Communicative Actions for Artificial Agents

Reference: Cohen, P. R. & Levesque, H. J. (1995). Communicative Actions for Artificial Agents. In Proceedings of the First International Conference on Multi-Agent Systems (ICMAS-95), San Francisco, June 1995, pp. 65–72. AAAI Press. Reprinted in J. M. Bradshaw (ed.), Software Agents (AAAI Press / MIT Press 1997), ch. 19. URL (AAAI PDF)

Summary

This paper is the high-water mark of mentalistic ACL semantics: the most explicit, systematic statement of the position that an agent communication act is a complex operator on the BDI states of sender and receiver, and that the semantics of an ACL performative is given by feasibility preconditions and rational effects expressed in modal logic over those mental states. Cohen and Levesque extend the Cohen–Levesque 1990 modal logic of intention into a logic of rational action in which speech acts are first-class actions whose definitions are derivable from more basic actions of attempting to bring about a state of affairs, together with assumed Gricean rationality on the part of both agents. The standard FIPA-ACL semantics in the FIPA Communicative Act Library Specification (FIPA00037) is essentially a streamlined adaptation of the Cohen–Levesque framework.

The mechanism is precise. A speech act e performed by speaker s toward hearer h has a feasibility precondition (e.g. s believes p, s believes h does not know p, s intends h to come to know p) and a rational effect (e.g. h believes p because h believes s sincerely informed). The semantics of inform, request, promise, commit, propose, and other performatives are derived by composition from the more primitive attempt: a request is an attempt to bring about that the hearer perform an action and that the hearer believe the speaker wants the action performed; an inform is an attempt to bring about that the hearer come to believe p and to know the speaker believes p; and so on. The framework is mathematically beautiful and ontologically heavy: it requires every speech act to be defined in terms of nested beliefs and intentions of speaker and hearer, often to several levels of nesting.

This is precisely why Singh 1998 writes the Rethinking critique. The Cohen–Levesque definitions are unverifiable in practice: no external observer can check that an agent believed p when it sent inform(p); the inferential web that fixes whether the agent “really” performed an inform speaks entirely about the agent’s mental state, which is exactly the inscrutable thing the protocol participants do not have access to. The paper is therefore the canonical negative example for CBCL and the commitment-based tradition: it shows what a fully worked-out mentalistic semantics looks like, and that shows why the field has had to move on. The right way to read it in 2026 is as the high statement of a coherent but unverifiable position, not as a blueprint to implement.

Key Ideas

Speech act = action on mental states: a communicative act is a complex action whose semantics is given by feasibility preconditions and rational effects expressed over the BDI states of speaker and hearer.
Attempt as the primitive: more elementary than the standard speech-act categories is the action of attempting — an agent attempts an action toward an end if and only if it performs the action with that goal and the belief that the action is the means.
Composition of performatives: standard performatives (inform, request, promise, propose, confirm, agree, refuse) are derived by composing attempt with specific mental-state preconditions and goals.
Sincerity and competence as background assumptions: the rational effects only follow if speaker and hearer are sincere (no lying) and competent (no false beliefs). When these fail, the framework’s predictions silently fail too.
Joint intentions in conversation: extends the 1990 framework with joint intentions — for conversational acts like agreement, both parties acquire a shared intention with mutual belief.
Verifiability is a known cost: the paper acknowledges that the mental-state preconditions are not externally observable; it argues this is the price of a real semantics rather than a behavioural surrogate.
Closest formal ancestor of FIPA: the FIPA-ACL CAL spec (FIPA00037) is a direct adaptation of this framework with light editorial smoothing.

Connections

Conceptual Contribution

Claim: Communicative acts can be given precise semantics by defining them as complex actions on the BDI states of sender and receiver, derived by composition from the primitive notion of attempt under shared rationality assumptions. The semantics of an ACL performative is its feasibility precondition and rational effect, expressed in modal logic over beliefs, goals, and intentions.
Mechanism: Extend the Cohen–Levesque 1990 modal logic of intention with a notion of attempt (an agent attempts an action toward an end iff it performs the action with that goal and the belief that the action serves the goal). Define each standard performative by composition: inform(s,h,p) requires s believes p, s believes h does not know p, s intends h to come to know p; the rational effect is that h comes to believe p by mutual recognition of s’s sincerity. Similar definitions for request, promise, propose, agree, refuse, with joint-intention machinery handling conversational acts.
Concepts introduced/used: Attempt (Cohen-Levesque), Feasibility Precondition, Rational Effect, Mentalistic Semantics, Joint Intentions, Sincerity Condition, Communicative Act Library.
Stance: foundational technical paper / formal-semantics manifesto.
Relates to: The closest formal ancestor of the FIPA Communicative Act Library (FIPA00037) — the FIPA spec is essentially a streamlined adaptation of this framework. It is the negative example against which the public-semantics / commitment-based line defines itself: Singh 1998 argues precisely that the BDI preconditions are unverifiable and that ACL semantics should be grounded in observable social commitments instead. Yolum & Singh 2002, Fornara & Colombetti 2004, and Singh 1999 develop the public alternative. CBCL then operationalises that alternative as a verified, trace-checkable, self-extending wire format — explicitly not what Cohen and Levesque built. The philosophical critique of mentalistic semantics runs deeper, through Sellars / Brandom / MIE — Cohen–Levesque takes mental states as pre-given semantic primitives, which is the move inferentialism rejects.

Tags

#cohen-levesque #mentalistic-semantics #bdi #speech-acts #acl #foundational #fipa-ancestor #classical-acl

Backlinks

Linked Pages

Inferentialism

The semantic view, developed in its modern form by Robert Brandom (building on Sellars, Wittgenstein, and Quine), that the meaning of a sentence is its role in the inferential practices of a community of speakers — what asserting it entitles you to assert, what claims it is incompatible with, what would entitle you to assert it. Reference, truth, and representational content are downstream of inferential articulation rather than upstream of it. The slogan: meaning is use, formalised. The position is the philosophical underwriting of the Public Semantics / Commitment-based Semantics line in agent communication — a worked-out Semantics-Without-Minds that lets a wire-format trace carry full semantic content without invoking sender or receiver mental states.

In this vault

Articulating Reasons - Brandom — entry point (the 1998 Locke Lectures in book form)
Making It Explicit - Brandom — the full treatise
Empiricism and the Philosophy of Mind - Sellars — Sellars’s Myth of the Given is the historical hinge
Philosophical Investigations - Wittgenstein — Meaning As Use / language-games
Two Dogmas of Empiricism - Quine — Semantic Holism
Material Inference
Deontic Scorekeeping
Semantics-Without-Minds
Public Semantics
Mentalistic Semantics
Commitment-based Semantics
ACL Rethinking Principles — Singh’s social-agency programme is the ACL-side analogue
An Ontology for Commitments in Multiagent Systems - Singh
CBCL - Safe Self-Extending Agent Communication — engineering realisation at wire-format granularity

Making It Explicit - Brandom

Making It Explicit: Reasoning, Representing, and Discursive Commitment

Reference: Brandom, R. B. (1994). Making It Explicit: Reasoning, Representing, and Discursive Commitment. Harvard University Press, Cambridge MA. ~700 pp. URL (Part One PDF, author-hosted) · Internet Archive · SEP: inferentialism

Summary

Making It Explicit is Brandom’s full statement of the inferentialist programme — the long, technical book that Articulating Reasons (2000) compresses into six lectures. Where the shorter book is the entry point, MIE is the reference manual: it works out, at the level of detail required to settle objections, how the basic discursive practice of giving and asking for reasons can serve as the foundation for an entire theory of meaning — including the parts (reference, truth, objectivity, intentionality) that representationalism takes as primitive. The book unfolds in two large parts: a pragmatic part, in which Brandom develops the deontic scorekeeping model of assertion and shows how it can recover everything one wants from a notion of speech act without recourse to mental states, and a semantic part, in which the recovery of singular terms, predicates, propositional content, and ultimately the de re / de dicto distinction is carried out in scorekeeping terms.

The book’s intellectual ancestry is openly stated: Quine on semantic holism and the analytic–synthetic collapse, Sellars on the Myth of the Given and the space of reasons, and Wittgenstein on meaning as use and language-games, all metabolised through a Hegelian appreciation of the social character of normativity. The technical innovation is to take Sellars’s insight — that the difference between a parrot trained to say “that’s red” and a person saying it is not phenomenological but inferential (a person can deploy the claim in the game of reasons) — and turn it into a full-scale semantic theory. The result is the most developed semantics-without-minds in the analytic tradition: a worked-out alternative to the mentalistic picture that has dominated philosophy of language since Searle and the early Cohen–Levesque tradition in ACL design.

For the agent-communication line, MIE is the place to send sceptics. The standard worry about public-semantics / commitment-based ACL design is that it gives up on “real” meaning in exchange for trace-checkability. Brandom’s answer, in a thousand pages, is no: deontic scorekeeping is not a thin behavioural surrogate for a richer mentalistic semantics — it is the foundation from which mentalistic talk is derivable. If Brandom is right, then Singh 1998’s move from BDI semantics to social-commitment semantics is not a retreat under pressure of verifiability; it is the correct place to ground meaning, with verifiability as a downstream bonus.

Key Ideas

Deontic scorekeeping as the basic discursive practice: speakers track, for themselves and each other, commitments (claims undertaken), entitlements (claims one is licensed to undertake), and incompatibilities (pairs of commitments that cannot both be entitled). Assertion is the basic move; the score is the running ledger.
Material inference as ground floor: inferences whose goodness is part of the meaning of the constituent terms (Pittsburgh is west of Princeton ⇒ Princeton is east of Pittsburgh) are prior to formal logical inference. Logic is a downstream expressive resource.
The expressive role of logic: conditionals, negation, and other logical vocabulary serve the function of making implicit inferential commitments explicit as new claims. This is the expressive (not foundational) role of logic.
De re / de dicto and singular terms: even classically representationalist topics — quantifying in, anaphora, singular reference — are reconstructed in scorekeeping terms, without taking reference as primitive.
Sapience without sentience: the distinction between concept-mongering creatures and the rest of nature lies in participation in the game of giving and asking for reasons, not in phenomenology.
Normative pragmatism: the social practice of holding one another accountable for commitments is the unanalysed foundation. Norms are instituted by the practice of scorekeeping, not read off antecedent facts.
Anti-representationalist but not anti-realist: truth, objectivity, and a mind-independent world are recovered from the perspectival structure of scorekeeping — not given up.

Connections

Conceptual Contribution

Claim: Linguistic meaning, including reference and objectivity, can be fully reconstructed from the social practice of deontic scorekeeping — undertaking, attributing, and tracking commitments and entitlements — without taking any mental state or representational primitive as basic.
Mechanism: A two-part construction. Pragmatic part: the basic act of asserting is the undertaking of a commitment; scorekeeping practices track commitments, entitlements, and incompatibilities. Semantic part: propositional content is the inferential role of a sentence in the scorekeeping practice; singular terms, predicates, de re / de dicto, and reference are recovered from the structure of perspectival scorekeeping. Logic is an expressive resource that makes implicit inferential commitments explicit.
Concepts introduced/used: Inferentialism, Deontic Scorekeeping, Material Inference, Commitment (Brandom), Entitlement (Brandom), Incompatibility (Brandom), Expressive Role of Logic, Sapience vs Sentience, De Re vs De Dicto, Normative Pragmatism, Semantics-Without-Minds.
Stance: foundational philosophical treatise.
Relates to: The book-length statement of which Articulating Reasons is the readable extract; read MIE only when the lectures leave a question unresolved. Genealogically continues the Wittgenstein / Sellars / Quine line — Sellars’s Myth of the Given is the antecedent move; Brandom’s scorekeeping is its destination. For agent communication, MIE is the deep philosophical underwriting of the public-semantics / commitment-based programme — Singh, Fornara & Colombetti, Yolum & Singh, and ultimately CBCL can all be read as engineering instantiations of fragments of the MIE picture.

Articulating Reasons - Brandom

Articulating Reasons: An Introduction to Inferentialism

Reference: Brandom, R. B. (2000). Articulating Reasons: An Introduction to Inferentialism. Harvard University Press. Based on the 1998 Locke Lectures (Oxford). URL · SEP entry on inferentialism

Summary

Articulating Reasons is the compact entry point to Brandom’s inferentialist programme — a semantics without minds in which the meaning of a sentence is its role in the inferential practices of a community of speakers, rather than a mental representation of how things stand or a Tarskian truth-condition fixed by reference. Where representationalism takes reference and truth as basic and explains inference downstream, Brandom inverts the order: the basic semantic fact is which moves count as good reasons for which other moves, and reference, truth, and propositional content are explained as features of discursive practice downstream of inferential articulation. The slogan is meaning is use, descended from Wittgenstein and Sellars, but Brandom upgrades it from a regulative idea into a worked-out pragmatist semantics.

The mechanism is a deontic scorekeeping account of assertion. To assert something is to undertake a commitment and to license other speakers to attribute that commitment back; the score every speaker keeps on every other is a record of which commitments are undertaken, which are licensed, and which are incompatible. The content of a claim is then exhaustively determined by the inferential articulation of those commitment relations: what entitles you to claim it, what it entitles you to claim, what claims it is incompatible with. The book unfolds this through six lectures — Toward an Inferentialist Semantics, Action / Reason / Inference, Insights and Blindspots of Reliabilism, What Are Singular Terms?, A Social Route from Reasoning to Representing, and Objectivity and the Normative Fine Structure of Rationality — extracting the spine of the 700-page Making It Explicit in a form readable in a week. The view explicitly avoids smuggling in mentalism: there are no beliefs or intentions in the foundations, only the public, trace-checkable practice of giving and asking for reasons.

For agent communication, inferentialism is the philosophical underwriting of the public-semantics programme: it shows that you can have a full theory of meaning — not just a thin behavioural sketch — without ever quantifying over mental states. Singh’s critique of FIPA-style mentalism gestures at this; Brandom delivers the goods. The natural pairing in this vault is with CBCL and the commitment-based semantics of Singh, Fornara, and Colombetti, all of which can be read as engineering realisations of Brandom’s deontic scorekeeping at wire-format granularity.

Key Ideas

Inferentialism: meaning is fixed by inferential role — what claims entitle a speaker to make, what they exclude, what claims entitle the speaker to make them — not by reference or truth-conditions, which are explained downstream.
Deontic scorekeeping: a speaker’s discursive score is the record of which commitments they have undertaken, which entitlements they have, and which incompatibilities apply. Assertion = undertaking a commitment + licensing attribution back to oneself.
Material vs formal inference: inferences like “Pittsburgh is west of Princeton, therefore Princeton is east of Pittsburgh” are materially good — their goodness is part of the meaning of west and east, not a downstream consequence of logical form plus reference.
Logical vocabulary is expressive, not constitutive: connectives like “if … then …” let speakers make explicit, in the form of claims, inferential commitments that were previously only implicit in practice. Logic is the technology for making practices explicit, not the foundation.
Sapience vs sentience: what distinguishes language-users from thermostats is participation in the game of giving and asking for reasons. No phenomenology required.
Singular terms and objectivity from social structure: even reference and the objectivity of claims (the gap between “what we take to be correct” and “what is correct”) are recovered from the structure of perspectival scorekeeping rather than imported as primitives.
Anti-representationalist but not anti-realist: inferentialism is compatible with robust truth, reference, and a mind-independent world — it just refuses to take those as semantic ground floor.

Connections

Conceptual Contribution

Claim: A complete theory of linguistic meaning can — and should — be built from the publicly observable practice of giving and asking for reasons, with no mental states (beliefs, intentions) in the foundations. Reference and truth are downstream of inferential articulation, not upstream of it.
Mechanism: Deontic scorekeeping: every participant in discourse maintains a score on every other participant tracking which commitments they have undertaken, which entitlements they hold, and which incompatibilities are in play. The content of a sentence is exhaustively given by its inferential articulation in this scorekeeping practice — what entitles you to assert it, what asserting it entitles you to, and what asserting it is incompatible with. Logical vocabulary is a downstream expressive layer that lets implicit inferential commitments be made explicit as further claims.
Concepts introduced/used: Inferentialism, Material Inference, Deontic Scorekeeping, Discursive Practice, Commitment (Brandom), Entitlement (Brandom), Incompatibility (Brandom), Sapience vs Sentience, Expressive Role of Logic, Semantics-Without-Minds.
Stance: foundational philosophical monograph / lecture series.
Relates to: The direct philosophical underwriting of the public-semantics / commitment-based line in agent communication: Brandom shows you can have a full theory of meaning — not just a thin behavioural sketch — without invoking mental states, which is precisely what Singh needs and what Cohen and Levesque’s mentalistic ACL semantics could not deliver. CBCL and the commitment-machine tradition can be read as engineering realisations of deontic scorekeeping at wire-format granularity: a CBCL trace is a deontic score, and a dialect contract names which inferential moves are licensed. Genealogically the book is the late chapter of the Wittgenstein / Sellars / Quine line; the Myth of the Given (Sellars) is the move that lets meaning bypass preconceptual reference, and Brandom shows how far that move actually carries.

Empiricism and the Philosophy of Mind - Sellars

Empiricism and the Philosophy of Mind

Reference: Sellars, W. (1956). Empiricism and the Philosophy of Mind. In Feigl & Scriven (eds.), The Foundations of Science and the Concepts of Psychology and Psychoanalysis (Minnesota Studies in the Philosophy of Science, vol. I, pp. 253–329). University of Minnesota Press. Reissued as a standalone book in 1997 with study guide by Brandom. URL (Ditext transcription) · SEP: Sellars

Summary

Sellars’s Empiricism and the Philosophy of Mind — often known by the abbreviation EPM — is the founding text of the Pittsburgh school of philosophy (Sellars, Brandom, McDowell) and the source of the move that makes semantics without minds possible. The paper’s central target is the Myth of the Given: the idea that knowledge must rest on a foundation of preconceptual, given sensory contents (sense data, qualia, immediate awareness) which are both non-inferential and epistemically authoritative. Sellars argues that this picture is incoherent: anything that could be epistemically authoritative — anything that could justify a belief — must already be conceptually articulated, and so cannot be preconceptual. There is no epistemic free lunch at the periphery; all knowledge lives inside the space of reasons.

The argument unfolds across sixteen sections. The early sections deconstruct sense-datum theory; the middle sections develop Sellars’s positive account of looking-talk (looks-red is parasitic on is-red, not the other way around); the late sections develop the famous Jonesean myth in which thoughts and inner episodes are introduced as theoretical posits modelled on overt speech, with sensory impressions as further theoretical posits modelled on the perceptible properties of physical objects. The Jonesean myth is Sellars’s positive reconstruction of mentalistic talk: mental states are not pre-given inner objects we somehow inspect, but theoretical entities whose semantic content is fixed by their inferential role — which means mentalistic vocabulary is parasitic on public language, not foundational for it. This single move — “the categories of inner episodes are modelled on the categories of intersubjectively available language” — is the historical hinge on which the inferentialist turn rotates.

For agent communication, EPM is the philosophical warrant for treating the wire as the semantic ground floor and the agent’s mind as a downstream theoretical posit. The standard worry about public-semantics ACLs is that they leave out “what the agent really meant”; Sellars’s answer is that “what the agent really meant” is itself a theoretical extrapolation from public discursive practice, not a pre-given inner episode the public practice approximates. The mentalistic ACL semantics that Sellars’s argument undermines is precisely the FIPA/Cohen–Levesque picture that Singh 1998 sets aside.

Key Ideas

The Myth of the Given: the foundationalist idea that knowledge rests on preconceptual, immediately-known sensory contents is incoherent. Anything that can justify a belief is already conceptually articulated; epistemic standing lives in the space of reasons.
Looks-talk is parasitic on is-talk: “X looks red to me” is not a more secure foundation than “X is red”; it is a hedge introduced after we have learned to deploy is-red, used when we want to undertake the commitment to a colour-impression without undertaking the commitment to the colour itself.
The Jonesean myth: a methodological fiction in which a community with only behavioural language develops mentalistic vocabulary by introducing thoughts (modelled on overt speech) and sensations (modelled on the perceptible properties of physical objects) as theoretical entities. The point: mentalistic talk is a theoretical posit, not a description of pre-given inner data.
The space of reasons: “In characterizing an episode or a state as that of knowing, we are not giving an empirical description of that episode or state; we are placing it in the logical space of reasons, of justifying and being able to justify what one says.” §36 — the most-quoted line in 20th-century epistemology.
Psychological nominalism: all awareness of universals, kinds, sorts, and resemblances is linguistic awareness — there is no preconceptual awareness of abstract entities.
Sapience over sentience: the distinction between concept-using creatures and others is participation in the game of reasons, not the having of qualia.

Connections

Conceptual Contribution

Claim: Knowledge cannot be grounded in preconceptual given sensory contents; epistemic standing requires conceptual articulation, which is inherently a public, language-involving achievement. Mentalistic vocabulary is a theoretical posit modelled on public discourse, not a description of pre-given inner data.
Mechanism: A dialectical demolition of sense-datum theory in §§1–7, a developmental account of looks-talk in §§10–20, and the Jonesean myth in §§48–63 in which mentalistic vocabulary is introduced into a behavioural community as a theory whose entities (thoughts, sensations) are modelled on already-public categories (overt speech, perceptible properties).
Concepts introduced/used: Myth of the Given, Space of Reasons, Psychological Nominalism, Sapience vs Sentience, Looking-Talk, Jonesean Myth, Theoretical Posit, Conceptual Articulation, Semantics-Without-Minds.
Stance: foundational philosophical paper.
Relates to: The historical hinge on which the entire inferentialist / Pittsburgh school turns. Brandom and MIE are the systematic development of the positive programme implicit in EPM’s negative demolition. The argument that mentalistic talk is parasitic on public language is the philosophical underwriting of Singh’s move from mentalistic to social-commitment semantics for ACLs, and of CBCL’s decision to ground meaning at the wire format rather than at the agent internals. The complementary moves in the same generation are Quine 1951 (against the analytic-synthetic distinction and for holism) and Wittgenstein 1953 (meaning as use).

CBCL - Safe Self-Extending Agent Communication

CBCL: Safe Self-Extending Agent Communication

Reference: O’Connor, H. (2026). LangSec Workshop, IEEE Security and Privacy Workshops (SPW 2026). arXiv:2604.14512v1 [cs.CR], 16 Apr 2026. Source file: oconnor-cbcl-langsec26.pdf. URL. Reference implementation: https://codeberg.org/anuna/cbcl-rs.

Summary

Building on McCarthy’s 1975/1982 Common Business Communication Language vision and the language-theoretic security programme of Sassaman, Patterson, Bratus and Locasto (Security Applications Of Formal Language Theory), this paper presents a contemporary CBCL: an agent communication language designed so that all messages — including runtime language extensions — remain within the deterministic context-free (DCFL) complexity class. The motivating diagnosis is that contemporary agent communication has slid up the Chomsky hierarchy without acknowledging the security cost: KQML and FIPA-ACL are CFL with informal extensibility, but MCP and LLM-based agent frameworks operate over inputs whose effective complexity is recursively-enumerable, where the validity of an arbitrary message is undecidable and “weird machines” (Exploit Programming - From Buffer Overflows To Weird Machines) become unavoidable. CBCL takes the opposite tack: minimal core (8 performatives — tell, ask, reply, hello, bye, ok, error, cancel) plus a homoiconic dialect mechanism that lets agents define, transmit, and adopt domain-specific vocabularies as first-class CBCL messages, with three machine-checked safety invariants — R1 (no recursion in dialect templates), R2 (declared resource bounds on depth, expansion size, verification time), R3 (core-vocabulary preservation) — that together guarantee DCFL preservation under arbitrary finite sequences of dialect installations.

The paper accompanies the design with a Lean 4 formalization (≈5,400 lines, 16 modules, 176 machine-checked theorems, zero sorry gaps, no custom axioms) covering parser correctness (soundness + completeness), R1–R3 verification, pipeline totality, and the central dcfl_preserved closure theorem; a verified parser binary cbcl-parse is extracted from the proofs. A separately-developed Rust reference implementation (cbcl-rs, ≈11,000 lines, no_std-compatible core) ships a hand-rolled O(n) parser, dialect verification engine, gossip-based dialect propagation (O(log n) convergence per Demers et al.), C FFI/WASM bindings, property-based and differential tests, and cargo-fuzz targets; differential tests cross-validate the Rust parser against the Lean-extracted binary, eliminating spec-implementation parser differentials. Five example dialects (precision agriculture, AI planning, cross-chain asset transfer, artifact management, email) are R1–R3-verified end-to-end. A draft IETF Internet-Draft specifying application/cbcl and a Nostr transport binding (cbcl-nostr) accompany the paper. The Discussion explicitly aligns the design with Singh’s social-agency programme: dialect installation is treated as a public commitment to the dialect’s declared semantics — semantic divergence becomes a breach of commitment, observable and accountable, rather than a hidden failure of shared mental state — sidestepping the unverifiable mentalistic semantics critique of Verifiable Semantics for ACLs.

Implementation status (post-paper, cbcl-rs). The reference implementation has shipped two further safety invariants the paper sketches as future work, plus a richer Lean formalisation: R4 (Integrity) — Ed25519-style signatures over canonical encodings via an algorithm-agnostic Signer trait, with three-valued install verdicts (Valid / Unsigned / Invalid) — and R5 (Contract Well-formedness) — optional (protocol …) and (shape …) clauses on a dialect, expressing causal Merkle DAG protocols and per-performative shape contracts; R5 enforces acyclicity, reachability from begin, performative definedness with ancestor closure for extends, step uniqueness, and depth-bound respect, all decidable in linear fuel at install time. The §VII-D structural-contracts vision is therefore live (SPEC-002, SPEC-003): verify_monotone, verify_all_is_meet, and verify_eventually_consistent are proved theorems showing causal-protocol verification is a lattice homomorphism that joins coordination-free under G-Set store merge — explicit CALM Theorem alignment. The Lean codebase has grown to 380+ declarations across 19 files (still zero sorry, only the standard axioms propext / Classical.choice / Quot.sound); the workspace ships 837 tests including 584 cbcl-core unit tests, 37 proptest cases, 21 differential integration tests against the Lean-extracted binary, libFuzzer harnesses, and cargo-mutants mutation testing at a 90% kill threshold. The crate layout has grown from the paper’s five to seven: the original cbcl-core / cbcl-parser / cbcl-cli / cbcl-wasm / cbcl-ffi plus cbcl-erl (Erlang/LFE binding, SPEC-009 — with SPEC-010 binding-conformance suite) and cbcl-arena (Agent Arena platform, SPEC-012 — composable referee on cbcl-lfe-router with capability-keyed message routing and signed receipt logs). A worked sealed-bid auction dialect (SPEC-004) demonstrates structural defence against false-claim manipulation — concrete evidence that the R5 contract layer is rich enough to encode mechanism-design integrity properties decidably. The earlier Scheme prototype (anuna-research/cbcl) is superseded; architecture decisions live as ADRs under .hence/ (purity boundary, parser library choice, error handling, WASM API surface, R4 adversarial review).

Key Ideas

DCFL as the Goldilocks complexity class: Regular is too weak for nested envelopes/dialects; general CFL admits ambiguous grammars and parser-differential attacks; context-sensitive is PSPACE-complete; Type-0 is undecidable. DCFL is the minimal class that supports nested structure with class-level unambiguity (parser equivalence under language evolution).
Homoiconic self-extension: Dialect definitions are themselves valid CBCL messages, parsed by the same recogniser used for ordinary communication — a single attack surface, no separate meta-language. Inspired by Racket’s #lang mechanism.
Three safety invariants R1–R3: declarative pattern-template substitution only (no recursion, no iteration, no reflection); declared resource bounds (depth ≤ 64, expansion ≤ 8192 chars, verification ≤ 1000 ms); the eight core performatives cannot be redefined.
DCFL preservation theorem: dialect invocations must appear inside a (lang name …) wrapper; the lang tag plus a unique dialect name forms a prefix-free partition that lets a deterministic pushdown automaton dispatch to the appropriate subgrammar without extra lookahead — circumventing the fact that DCFLs are not closed under union in general. Mechanised in Lean 4 as dcfl_preserved.
Lean 4 formalization with extraction: 176 theorems, 0 sorry gaps, no custom axioms; the verified parser binary cbcl-parse is extracted from the proofs and runs the same fuel-bounded recursive-descent parser as the model.
Rust reference implementation: cbcl-core (no_std, no unsafe), cbcl-parser, cbcl-cli, cbcl-ffi, cbcl-wasm. Differential tests against the Lean-extracted binary; cargo-fuzz over five entry points.
Eight core performatives (tell, ask, reply, hello, bye, ok, error, cancel) plus four message categories (simple, meta, lang-scoped, wrapped); keyword parameters in Common-Lisp style (:thread, :in-reply-to).
Single-pass template expansion: terminates in time linear in the template plus argument size; not Turing-complete; output is not fed back into the expander, ruling out unbounded re-expansion.
Epidemic dialect propagation: gossip-based with Demers et al.’s O(log n) convergence bound; agents independently verify R1–R3 and signatures before installing.
Canonical serialization per RFC 9804 for cryptographic operations — deterministic byte representation as a precondition for signature verification.
Dialect identity by content hash: name collisions resolved by canonical-form hash; downgrade attacks rejected at installation.
Self-expression vs self-adaptation (Zambonelli et al.): traditional ACLs support only parameter tuning within fixed structure; CBCL is a self-expressive protocol whose vocabulary structurally evolves under safety constraints.
Singh-aligned reading of dialect installation: a public commitment to declared semantics, with :examples clauses providing machine-checkable behavioural anchors — semantic divergence as observable breach rather than hidden mental-state mismatch.
Stated limitations: DCFL ceiling means no recursive transformations, no cross-field references (e.g. checksums over fields), no aggregation over variable-length collections, no context-sensitive validation. Standish-taxonomy paraphrastic only — no Orthophrase, no Metaphrase. Trust infrastructure (key distribution, revocation) and dialect-curation policy left to deployment.
Structural-contracts extension (sketched in §VII-D, shipped post-paper as R4 + R5): Ed25519-style dialect signatures plus protocol constraints as causal Merkle DAGs over performative-typed messages, with Visibly Pushdown Languages for shape constraints and coordination-free monotonic verification over an append-only store. Lean-mechanised lattice-homomorphism theorems (verify_monotone, verify_all_is_meet, verify_eventually_consistent) establish that replica verdicts join under G-Set merge.

Connections

Common Business Communication Language — McCarthy’s 1975/1982 origin; CBCL is the formally-verified realisation of that vision.
Security Applications Of Formal Language Theory — Sassaman et al.’s LangSec foundations.
Proof-Carrying Code - Necula — Necula 1997, the architectural ancestor of CBCL’s R4 split (host runs a small certified verifier; producer ships the proof).
Enforceable Security Policies - Schneider — Schneider 2000, the formal warrant for R5 monotone-verdict trace monitoring.
An Axiomatic Basis for Computer Programming - Hoare — Hoare 1969, root of the contract-based verification line CBCL inherits.
Authentication in Distributed Systems - Lampson Abadi Burrows Wobber — Lampson et al. 1992, the Speaks-For Calculus for delegated commitments.
Articulating Reasons - Brandom — Brandom 2000, the philosophical underwriting of Public Semantics (entry point).
Making It Explicit - Brandom — Brandom 1994, the full inferentialist treatise.
Empiricism and the Philosophy of Mind - Sellars — Sellars 1956, the Myth of the Given that makes Semantics-Without-Minds possible.
Philosophical Investigations - Wittgenstein — Wittgenstein 1953, Meaning As Use / language-games / rule-following.
Two Dogmas of Empiricism - Quine — Quine 1951, Semantic Holism.
Assertion - Stalnaker — Stalnaker 1978, Common Ground update semantics — operational analogue of CBCL’s verdict ledger.
Languages and Language - Lewis — Lewis 1975, Convention of Truthfulness picture of how an abstract language gets in force in a population.
Communicative Actions for Artificial Agents - Cohen Levesque — Cohen & Levesque 1995, the Mentalistic Semantics high-water mark CBCL deliberately is not.
FIPA-ACL Specifications — the engineering of FIPA-ACL (envelope, conversation-id, ontology slot) CBCL inherits; the semantics it replaces.
An Ontology for Commitments in Multiagent Systems - Singh — Singh 1999, the formal commitment ontology CBCL’s dialect contracts instantiate.
Jones-Sergot Normative Systems — Jones & Sergot 1993, the Counts-As Relation that gives wire events institutional meaning under a dialect contract.
Exploit Programming - From Buffer Overflows To Weird Machines — weird-machine analysis CBCL is designed to preclude at the parser layer.
PKI Layer Cake - Kaminsky Patterson Sassaman — concrete parser-differential attacks; CBCL’s class-level unambiguity rules these out at the grammar level.
The Halting Problems of Network Stack Insecurity
A Language-Based Approach To Prevent DDoS
LangSec
KQML as an Agent Communication Language
KQML - A Language And Protocol For Knowledge And Information Exchange
FIPA-ACL
ACL Rethinking Principles — Singh’s social-agency critique that CBCL’s “dialect installation as public commitment” inherits.
Agent Communication Languages - Rethinking the Principles
Verifiable Semantics for ACLs
A Common Ontology Of ACLs
Commitment-based Semantics
The State of the Art in Agent Communication Languages
Trends in Agent Communication Language
Toward Principles for the Design of Ontologies Used for Knowledge Sharing — Gruber’s ontological-commitment principle CBCL inherits.
Some Philosophical Problems from the Standpoint of Artificial Intelligence — McCarthy & Hayes’s representation/computation separation.
Elephant 2000 - A Programming Language Based on Speech Acts — McCarthy’s intra-program speech-act counterpart to CBCL’s inter-organisational vision.
Adjectival Modifiers
S-expression
Homoiconicity
Code as Data
Creating Languages in Racket — Flatt’s #lang mechanism that inspired CBCL’s homoiconic self-extension.
Extensibility in Programming Language Design - Standish
Language Extensibility Taxonomy
Paraphrase
Orthophrase
Metaphrase
Self-Expression
Self-Adaptation Self-Expression Self-Awareness ASCENS
Dialects and Idiolects
Keeping CALM - When Distributed Consistency is Easy — CALM theorem underwriting the forthcoming coordination-free contracts extension.
Visibly Pushdown Languages
MCP Landscape Security Threats And Future Research Directions
Survey Of AI Agent Protocols
Survey Of Agent Interoperability Protocols
ClawWorm Self-Propagating Attacks Across LLM Agent Ecosystems — concrete LLM-agent worm whose root-cause analysis CBCL’s lang-scoped provenance addresses.
Why AI Agents Communicate In Human Language
Why Do Multi-Agent LLM Systems Fail
Gossiping in Distributed Systems
Gossip-based Aggregation in Large Dynamic Networks

Conceptual Contribution

Claim: Agent communication languages can be simultaneously expressive, runtime-extensible, and tractably verifiable iff every message — including those that extend the language — is constrained to the deterministic context-free language class; this constraint is compatible with first-class self-extension, can be machine-checked end-to-end, and converts the unverifiable-mental-state problem of mentalistic ACLs into a public-commitment problem at the protocol layer.
Mechanism: Eight-performative core grammar (LL(1), DCFL); homoiconic dialect mechanism — dialect definitions are valid CBCL messages with extend clauses describing pattern-template substitutions; three safety invariants R1–R3 enforced at installation (no recursion via DFS cycle detection, declared resource bounds, core-vocabulary preservation); (lang name …) wrapper providing prefix-free deterministic dispatch into per-dialect sub-grammars so the union remains DCFL. Lean 4 formalization (LeanCbcl, ~5,400 LoC, 176 theorems) covering parser soundness/completeness, R1–R3, pipeline totality, and dcfl_preserved; verified parser extracted to a runnable binary (cbcl-parse). Rust reference implementation (cbcl-rs, ~11,000 LoC) with a ResourceContext-tracked single-pass expander, gossip-based dialect propagation (O(log n) per Demers et al.), canonical RFC-9804 serialization for signing, algorithm-agnostic Signer trait, C FFI / WASM bindings, property-based + differential tests, fuzz targets. Draft IETF application/cbcl Internet-Draft and Nostr transport binding.
Concepts introduced/used: Deterministic Context-Free Language, LangSec, Homoiconicity, S-expression, Dialects and Idiolects, Performatives, Self-Expression, Paraphrase, Orthophrase, Metaphrase, Visibly Pushdown Languages, CALM Theorem, Commitment-based Semantics, Public Semantics, Verifiable Semantics, Adjectival Modifiers, Ontological Commitment, Lean 4, Property-Based Testing, Parser Differential Attack, Weird Machine, Gossip Protocols, Canonical Serialization, Nostr, hence
Stance: engineering / formal-methods, with explicit position-taking on the agent-communication design space
Relates to: Realises McCarthy’s Common Business Communication Language vision (1975/1982) by giving formal safety guarantees McCarthy could only gesture at. Sits squarely in the LangSec programme of Security Applications Of Formal Language Theory and Exploit Programming - From Buffer Overflows To Weird Machines, extending it from input-validation analysis to protocol design — claiming, plausibly, to be the first ACL designed from LangSec principles and the first to demonstrate that LangSec is compatible with runtime self-extension. Inherits the DCFL-vs-ambiguous-CFG argument from PKI Layer Cake - Kaminsky Patterson Sassaman and applies it at the message layer rather than the certificate layer. Builds explicitly on Singh’s social-agency critique (ACL Rethinking Principles) and Wooldridge’s verifiability programme (Verifiable Semantics for ACLs) by treating dialect installation as a public commitment whose semantics are anchored by the :examples clause — a machine-checkable analogue of the commitment-trace conformance that Flexible Protocol Specification and Execution (Yolum & Singh) and Commitment Machines - Yolum and Singh establish for protocol actions. Where Pact - A Choreographic Language for Agentic Ecosystems takes the individual-rationality fork to answer “why follow a protocol?”, CBCL takes the publicness/verifiability fork: the meaning of a message is fully determined by the formal grammar plus declared semantics, with no mental-state inference required. Inherits Gruber’s ontological-commitment architecture but replaces “out-of-band agreement” with in-protocol propose/query/teach. The extensibility design draws on Creating Languages in Racket (Flatt’s #lang) and respects the boundary set by Extensibility in Programming Language Design - Standish: paraphrastic only, deliberately excluding orthophrase/metaphrase to keep the attack surface bounded. The forthcoming structural-contracts extension uses Visibly Pushdown Languages for shape constraints and the CALM Theorem for coordination-free verification — a natural bridge to commitment-machine semantics. The LLM-agent threat-model framing (ClawWorm Self-Propagating Attacks Across LLM Agent Ecosystems, MCP Landscape Security Threats And Future Research Directions) positions CBCL as the structural alternative to MCP/JSON-RPC-with-natural-language: same extensibility, vastly tighter security envelope.

An Ontology for Commitments in Multiagent Systems - Singh

An Ontology for Commitments in Multiagent Systems: Toward a Unification of Normative Concepts

Reference: Singh, M. P. (1999). An Ontology for Commitments in Multiagent Systems: Toward a Unification of Normative Concepts. Artificial Intelligence and Law 7(1): 97–113. Kluwer. DOI · Author copy via Academia.edu · Singh publications (NCSU)

Summary

This paper is the formal core of Singh’s commitment-based programme — a piece that sits between the polemical Rethinking the Principles (1998) and the operationalised commitment machines line (Yolum & Singh 2002). Singh argues that the multiplicity of normative concepts used across MAS, deontic logic, and law — obligation, permission, prohibition, promise, contract, delegation, cancellation, release — can be unified by taking the social commitment as the basic ontological primitive and reconstructing the rest as patterns over commitments. A social commitment is a four-place relation: a debtor is committed to a creditor for the fulfilment of some condition in the context of a particular institution or social scope. Once these four roles are fixed, the standard normative operations — create, discharge, cancel, release, delegate, assign — become commitment-state transitions, and the deontic vocabulary becomes a derived layer over the commitment substrate.

The construction is deliberately public: commitments live in the social state, not in the heads of any agent. A commitment exists when a publicly observable act has created it (a promise speech act, a contract signing, an assertion under appropriate sincerity context); it persists until a publicly observable act has discharged or cancelled it. The truth-conditions for “agent A is committed” are externally checkable: they reference the social record, not A’s mental state. This is the exact alternative to the mentalistic semantics of FIPA / Cohen and Levesque 1995 that Rethinking the Principles called for. The paper also sets up the bridge to law: Singh notes the close fit with Jones and Sergot’s “count-as” relation, with deontic logic, and with the speaks-for tradition in distributed systems — establishing commitments as a unifying normative substrate across philosophy, law, MAS, and computer security.

For CBCL and the broader public-semantics line, this is the ontology document: it defines what “commitment” means precisely enough that protocol designers can map performatives onto commitment-state transitions and verifiers can monitor compliance from a transcript. The four-place structure (debtor, creditor, condition, context) maps almost directly onto the ledger-of-commitments architecture in Fornara & Colombetti 2004 and the dialect contracts in CBCL. The paper is also the place to cite when arguing that commitment-based ACL semantics is not merely a behavioural surrogate but a real normative theory with established connections to legal and deontic logic.

Key Ideas

Commitment as the primitive normative concept: a four-place relation C(debtor, creditor, condition, context) — agent x is committed to agent y for the fulfilment of condition q in the social context s. The four roles must always be specified; commitments without a creditor are degenerate.
Standard commitment operations: create (a new commitment comes into being via a public act), discharge (the condition is satisfied), cancel (the debtor unilaterally retracts, possibly incurring meta-commitment), release (the creditor waives), delegate (the debtor passes the obligation to a third party with creditor consent), assign (the creditor passes the entitlement).
Conditional commitments: CC(x, y, p ⊃ q, s) — x is committed to y to bring about q if p holds. The conditional structure handles contracts, contingent obligations, and protocol-state dependencies.
Discharge by satisfaction: a commitment is discharged when its condition is satisfied (in the relevant social interpretation); discharge is monotone — once discharged, the commitment is closed.
Deontic vocabulary as derived: obligation, permission, prohibition, right, and duty are reconstructable from commitment patterns plus the relevant institutional context.
Public, externally checkable semantics: commitments are facts about the social record, not about agent mental states. Verification is by inspection of the transcript and the institutional rules.
Bridges to legal informatics and deontic logic: the framework is explicitly compatible with Jones and Sergot’s count-as relation and with classical deontic-logic operators, positioning commitments as the unifier across philosophy, law, MAS, and distributed-security normative reasoning.

Connections

Conceptual Contribution

Claim: The proliferation of normative concepts across MAS, deontic logic, and law can be unified by taking the social commitment — a four-place relation C(debtor, creditor, condition, context) — as the basic primitive and reconstructing obligation, permission, prohibition, contract, and delegation as commitment patterns. Commitments are public: their existence is determined by observable acts and observable conditions, not by agent mental states.
Mechanism: Define commitments as four-place relations (debtor / creditor / condition / context) and conditional commitments analogously. Specify the operations create / discharge / cancel / release / delegate / assign as commitment-state transitions. Show how standard deontic-logic operators and standard legal concepts (promise, contract, breach, novation) reduce to patterns over these primitives. Sketch the bridge to Jones and Sergot’s count-as analysis of institutional facts.
Concepts introduced/used: Social Commitment, Conditional Commitment, Commitment Operations (create / discharge / cancel / release / delegate / assign), Debtor, Creditor, Condition, Context (Commitment), Deontic Reduction.
Stance: foundational technical paper / unifying ontology.
Relates to: The formal statement of the programme Singh 1998 argued for polemically; the bridge to the operational accounts in Yolum & Singh 2002, Yolum & Singh 2002b, and Fornara & Colombetti 2004. The philosophical complement is Brandom: Singh’s commitments are precisely the commitment leg of Brandom’s deontic scorekeeping triple. The legal complement is Jones & Sergot 1993 — count-as gives the institutional grounding for what makes a publicly observable act count as creating a commitment. The distributed-systems complement is the speaks-for tradition (Lampson et al. 1992) — credentials and delegated assertion authority are commitment patterns of the same family. CBCL’s dialect contracts and verdict ledger directly instantiate this ontology at wire-format granularity.

A Commitment-Based Approach to Agent Communication

Reference: Fornara, N. & Colombetti, M. (2004). Applied Artificial Intelligence 18(9–10): 853–867. DOI: 10.1080/08839510490509054. The journal article is paywalled; the open-access AAMAS-02 conference precursor — Operational Specification of a Commitment-Based Agent Communication Language (pp. 535–542) — captures the same model and is the locally archived source. Source file: fornara-colombetti-aamas02.pdf. URL

Summary

Fornara and Colombetti develop an object-oriented operational semantics for an Agent Communication Language grounded entirely in social commitments, intended for open environments populated by self-interested, heterogeneous agents who cannot be assumed to share an honest mental architecture. A Commitment is an abstract data type with fields Identifier, Debtor, Creditor, State ∈ {empty, cancelled, precommitment, conditional, active, fulfilled, violated}, Content (a temporal proposition), Condition (another temporal proposition), and Time-out. Its evolution is given by an explicit finite-state machine driven by two kinds of transitions: agent-invoked methods (mc, mp, ap, cc, cp, rp) and event-driven update rules triggered when the truth value of the content or condition resolves.

The authors’ key innovation over the Yolum-Singh treatment is the precommitment state, which models the social situation a directive speech act creates: the speaker cannot directly commit the hearer, so a request instantiates a precommitment whose debtor is the hearer; the hearer either accepts it (turning it into an active or conditional commitment), rejects it, fulfills it implicitly by performing the action, or lets the time-out elapse. This machinery yields uniform commitment-based definitions for Searle’s main illocutionary categories — assertives (inform, informIf, informRef), commissives (promise, conditionalPromise), and directives (request, conditionalRequest, accept, reject, yes/noQuestion, whQuestion) — and lets a propose act be defined compositionally as a conditional request conjoined with a conditional promise. A worked auction-style proposal protocol is given as an interaction diagram whose state contents are computed from the speech-act definitions, and whose soundness is checked by requiring that all final-state commitments be empty, fulfilled, or violated.

Key Ideas

Commitment-as-object: a commitment is an abstract data type with a state in {e, c, p, cc, a, f, v} whose dynamics are described by an explicit FSM.
Temporal proposition class: the content/condition of a commitment is a sentence + time interval + ∀/∃ mode + state, resolved by a domain “notifier” — separating what is committed from when and how its truth is observed.
Precommitment models directive speech acts: a request creates C(p, hearer, speaker, P|Q) that the hearer can accept (ap), reject (rp), implicitly fulfil (update rule 5), or let time out.
Conditional commitment with a temporal condition becomes active when the condition is satisfied and is automatically cancelled if the condition fails.
Five update rules link the truth-state of content and condition propositions to commitment-state transitions (active→fulfilled/violated, conditional→active/cancelled, precommitment→fulfilled).
Searle’s taxonomy of illocutionary acts is recovered by composition: inform, promise, request, accept/reject, yes/noQuestion, whQuestion, propose.
Soundness of an interaction protocol is checked by an interaction diagram in which every final state’s commitments are empty, fulfilled, or violated — a structural correctness criterion for negotiation protocols.
The notion of a conversational commitment (a meta-commitment to react to interlocutor speech acts) is sketched as the principled justification for the time-out field.

Connections

Conceptual Contribution

Claim: Speech-act semantics for an ACL should be specified operationally — as state-machine transitions over a public commitment data type — so that meaning is independent of any agent’s internal mental architecture, observable to third parties, and compositional across the speech-act taxonomy; in particular, the directive family requires a dedicated precommitment state because no agent can unilaterally commit another.
Mechanism: Define an abstract Commitment class with seven explicit states and a transition FSM driven by methods (mc/mp/ap/cc/cp/rp) plus five event-driven update rules that read truth-states of Temporal Proposition objects; define each Searle category by a single-line operation on commitment objects (inform := mc(a,b,P,T), request := mp(a,b,P,T), propose := conditionalRequest ∧ conditionalPromise, etc.); validate interaction protocols structurally via a state-content interaction diagram in which final-state commitments must all be empty/fulfilled/violated.
Concepts introduced/used: Commitment, Social Commitment, Precommitment, Conditional Commitment, Temporal Proposition, Commitment-Based Protocol, Commitment-based Semantics, Public Semantics, Verifiable Semantics, Speech Act Theory, Directives, Conversation Protocols, Interaction Protocols, Open Multi-Agent Systems, Conversational Commitment
Stance: formal-semantic / engineering
Relates to: Closest neighbour is Flexible Protocol Specification and Execution (Yolum & Singh, AAMAS-02) — the authors explicitly compare the two approaches: where Yolum-Singh use the Event Calculus and an abductive planner over create/discharge/cancel/release/assign/delegate, Fornara-Colombetti use an OO/FSM data type and add the precommitment apparatus to cover directives. Both belong to the social-semantics programme catalysed by ACL Rethinking Principles and formalised verifiability-style by Verifiable Semantics for ACLs; both are subsumed under the role-based unification of A Common Ontology Of ACLs. Repudiates the mentalistic line of FIPA-ACL / Intention Is Choice with Commitment for interoperable ACL semantics while keeping speech-act theory (Speech Acts - An Essay in the Philosophy of Language, A Taxonomy of Illocutionary Acts) as the organising taxonomy. The 2004 Applied AI version this entry primarily cites elaborates the AAMAS-02 model with extended treatment of negotiation protocols and the soundness-via-conversational-commitment programme that the authors’ later artificial-institutions work develops.

Tags

Commitment Machines - Yolum and Singh

Commitment Machines

Reference: Yolum, P. & Singh, M.P. (2002). Intelligent Agents VIII: Agent Theories, Architectures, and Languages (ATAL-01), LNAI 2333, pp. 235–247. Springer. (A preliminary version appeared in WET-ICE 2000.) Source file: yolum-singh-2002-commitment-machines.pdf. URL

Summary

Yolum and Singh propose commitment machines (CMs) as a protocol formalism that, unlike finite-state machines or Petri nets, attaches declarative meaning to states and actions in terms of the participants’ Social Commitments. A CM is a triple ⟨M, Δ, F⟩ of a finite minimal set of meanings (formulas in a propositional language extended with a commitment operator Cₓp and a strict-implication operator ;), a set of actions ⟨a : e⟩ whose effect e is itself a meaning, and a set of consistent final meanings. Transitions are not enumerated — they are inferred from the logical consequences of applying an action’s effect to the current meaning. The running example is the NetBill Protocol, specified by atomic propositions (request, goods, pay, receipt) and abbreviations for conditional commitments (accept = C_c(goods ; pay), promiseGoods = C_m(accept ; goods), etc.); three reasoning rules govern how commitments evolve as content propositions are made true.

The paper’s central technical contribution is a compilation procedure that turns any complete CM (one whose meaning set is closed under antecedence) into a deterministic FSM that can be executed in constant space without commitment reasoning at run time. The procedure is shown sound (Theorem 2 — every realised computation is generated by the source CM) and complete (Theorem 3 — every CM-generated computation has a semantically-strongest, efficient FSM-realised counterpart from true), via a chain of lemmas about semantic superiority, efficient computations, and endpoint equivalence. Because the meanings of states are explicit, agents executing the CM directly can plan paths through the protocol that exploit opportunities (e.g. a merchant proactively quoting without a request, “try before you buy” deals) and handle exceptions, recovering autonomy that pure-token FSM/Petri-net specifications eliminate.

Key Ideas

Commitment machine ⟨M, Δ, F⟩: state space is a finite minimal set of meanings (formulas) rather than tokens; actions ⟨a : e⟩ carry effect-meanings; final states are a consistent subset of meanings.
Inferred transitions: q ⊨_⟨a:e⟩ r iff (q ∧ e) ⊢ r — transitions are derived from logical entailment, not enumerated edges.
No fixed start state: a CM has no s₀; participants may begin from any meaning whose commitments they accept (typically true).
Three reasoning rules over commitments: (1) Cₓp discharges when p holds; (2) Cₓ(p ; r) collapses to base-level Cₓr when p holds; (3) Cₓ(p ; r) ceases when r holds before p, with no new commitment.
Compilation to deterministic FSM under two restrictions: (R1) no transition mᵢ → mⱼ if mᵢ ⊢ mⱼ (no information-free moves); (R2) the target meaning must dominate all alternatives entailed by the action (forcing maximal information).
Completeness requires “complete” CMs — meaning set closed under antecedence — so that a unique strongest target meaning always exists; trivially achieved by closing under conjunction.
Soundness, completeness, determinism established as theorems over the computation abstraction (sequences of meanings interleaved with actions); computations are compared by semantic superiority and endpoint equivalence rather than literal action-sequence equality.
Flexibility recovered for free: since states encode meanings, agents can skip steps, reorder, or take unsolicited shortcuts whenever the resulting meaning is still in M and the path to a final meaning still exists.

Connections

Conceptual Contribution

Claim: Multi-agent protocols should be specified by giving states and actions declarative meaning in terms of the participants’ commitments — not by enumerating legal token sequences — and any such specification can be soundly and completely compiled to a deterministic FSM, recovering executability without forfeiting flexibility, autonomy, or the ability to handle exceptions and exploit opportunities.
Mechanism: A propositional language with a commitment operator Cₓ and strict-implication ;; meaning sets M and final-meaning sets F (consistent w.r.t. logical consequence); action effects given as meanings; transitions inferred via (q ∧ e) ⊢ r. Compilation Procedure 1 maps ⟨M, Δ, F⟩ → ⟨S=M, Σ={a}, s₀=true, Q=F, δ⟩ under the two information-monotonicity restrictions; Procedure 2 promotes a computation to its semantically strongest counterpart, Procedure 3 removes redundant self-transitions, yielding efficient semantically-strongest computations that are realised by the compiled FSM. Soundness (Thm 2), determinism (Thm 1), and completeness for complete CMs (Thm 3) are proved.
Concepts introduced/used: Commitment Machines, Commitment-Based Protocol, Commitment-based Semantics, Conditional Commitment, Social Commitment, Public Semantics, Verifiable Semantics, NetBill Protocol, Endpoint Projection (structural analogue), Conversation Protocols, Speech Act Theory
Stance: formal-semantic / engineering
Relates to: Direct precursor and structural sibling of Flexible Protocol Specification and Execution (Yolum & Singh, AAMAS-02), which lifts the same six commitment operations (Create / Discharge / Cancel / Release / Assign / Delegate) into the Event Calculus and adds an abductive planner; ATAL-01 here is the FSM-compilation half of that programme. Companion to A Commitment-Based Approach to Agent Communication (Fornara & Colombetti, AAMAS-02 / AAI-04), which gives an OO/FSM operational semantics for the same primitives plus a precommitment state for directives. Carries forward the social-agency programme of ACL Rethinking Principles (Singh 1998) and answers Wooldridge’s challenge in Verifiable Semantics for ACLs by grounding meaning in publicly-observable commitment formulas rather than agent mental state. The Discussion explicitly contrasts with Smith et al.’s joint-intention–based protocols (mental constructs vs. social constructs) — the same fork that Intention Is Choice with Commitment anchors on the mental side. Structurally a direct analogue of choreographic Endpoint Projection: both compile a globally-specified protocol artefact to a per-role executable, the CM/FSM compilation losing declarative meaning for runtime efficiency much as endpoint projection loses the global view for distributable execution. This makes ATAL-01 the load-bearing reference for the constructive synthesis suggested in the Pact - A Choreographic Language for Agentic Ecosystems entry — choreographies could carry both communication structure (Pact-side) and a CM-style commitment trace (Singh-side), with one compilation step yielding both deadlock-freedom and conformance-checkability.

Tags

ACL Rethinking Principles

Agent Communication Languages: Rethinking the Principles

Reference: Munindar P. Singh (1998). IEEE Computer, December 1998, pp. 40-47. Source file: computer-acl-98.pdf. URL

Summary

Singh surveys the state of Agent Communication Languages (ACLs) such as KQML and FIPA/Arcol, and argues that their dominant mental-agency semantics (defining communicative acts in terms of beliefs and intentions) is conceptually unsatisfying and practically untestable because we cannot read agents’ minds. He proposes a conceptual shift to social agency: ACL semantics should be grounded in a public perspective on commitments, roles, and societies, so compliance with the standard is observable and testable.

The paper maps the ACL design space along two critical dimensions — meaning (perspective, type, basis, context, coverage of communicative acts) and agent construction (design vs. execution autonomy) — and shows how both KQML and Arcol emphasize private, mental-state semantics and thus fail to enable true heterogeneous interoperation. Singh’s alternative emphasizes protocols, roles, and “society management” infrastructure as a richer public substrate for ACLs.

Key Ideas

Mental-agency ACL semantics (KQML, Arcol, early FIPA) cannot be verified without inspecting agent internals.
ACLs need a public perspective, conventional meaning, pragmatics, and full coverage of communicative act categories.
Seven categories of communicative acts: assertives, directives, commissives, permissives, prohibitives, declaratives, expressives.
Social agency replaces BDI with commitments, roles, and societies as the semantic basis.
Dialects/idiolects arise when only private perspectives are considered.

Connections

FIPA-ACL
FIPA-ACL Specifications
KQML
Speech Act Theory
Agent Communication Languages
Multi-Agent Systems
Communicative Actions for Artificial Agents - Cohen Levesque — the Mentalistic Semantics high-water mark Singh is critiquing
An Ontology for Commitments in Multiagent Systems - Singh — Singh’s own formal sequel: the four-place commitment ontology
Commitment Machines - Yolum and Singh
A Commitment-Based Approach to Agent Communication
Articulating Reasons - Brandom — the philosophical underwriting of public, commitment-based semantics
Making It Explicit - Brandom
Jones-Sergot Normative Systems — Counts-As Relation for institutional grounding of commitments
CBCL - Safe Self-Extending Agent Communication — O’Connor 2026: contemporary realisation of Singh’s social-agency programme (dialect installation as public commitment) in a Lean-verified LangSec-grounded ACL.

Conceptual Contribution

Claim: Agent Communication Language semantics must abandon mental agency (beliefs/intentions) and be grounded in a public, social perspective (commitments, roles, societies) in order to be testable and support heterogeneous interoperation.
Mechanism: Surveys KQML, Arcol, FIPA; lays out a two-dimensional design space (meaning × agent construction); shows that mental-state semantics cannot determine compliance; proposes social-agency framework using protocols, roles, and “society management” infrastructure.
Concepts introduced/used: Mentalistic Semantics, Public Semantics, Social Agency, Commitments, Communicative Acts, Verifiable Semantics, Interoperability, Dialects and Idiolects
Stance: critique / foundational
Relates to: Direct antecedent to Verifiable Semantics for ACLs (Wooldridge) which formalises the verification problem Singh names. Sharpens the critique of the mentalistic approach underlying KQML Overview and FIPA-ACL, and motivates commitment-based frameworks such as Agent Communication And Institutional Reality.

Tags

Commitment-based Semantics

Approach that grounds ACL message meaning in public social commitments rather than private mental states — making conformance verifiable.

In this vault

ACL Rethinking Principles
Agent Communication Languages - Rethinking the Principles
Agent Communication And Institutional Reality
A Common Ontology Of ACLs
Public Semantics
Mentalistic Semantics
Flexible Protocol Specification and Execution
A Commitment-Based Approach to Agent Communication
CBCL - Safe Self-Extending Agent Communication — modern LangSec-grounded ACL inheriting Singh’s social-agency programme; dialect installation as public commitment

Public Semantics

ACL semantics grounded in externally observable facts (commitments, roles, institutional state) rather than private mental state.

In this vault

ACL Rethinking Principles
Agent Communication And Institutional Reality
Commitment-based Semantics
Mentalistic Semantics
CBCL - Safe Self-Extending Agent Communication — dialect installation as a public commitment

FIPA-ACL Specifications

Reference: Foundation for Intelligent Physical Agents (2002). FIPA ACL Message Structure Specification (FIPA00061) and FIPA Communicative Act Library Specification (FIPA00037). Geneva, December 2002. (FIPA was absorbed into the IEEE Computer Society in 2005; specifications remain the canonical reference.) FIPA00061 (Message Structure) · FIPA00037 (Communicative Act Library) · FIPA00067 (Agent Message Transport) · IEEE FIPA standards committee

Summary

The FIPA-ACL specifications are the standards-track distillation of the late-1990s mentalistic ACL programme: the wire format and semantics that “ended up shipping” as the canonical example of an industry-grade agent communication language. The suite splits into three documents that matter for ACL design. FIPA00061 specifies the message structure — the surface syntax of an ACL message as a parameterised performative envelope with :sender, :receiver, :content, :language, :ontology, :protocol, :conversation-id, :reply-with, :in-reply-to, :reply-by, and a small set of related parameters. FIPA00037 specifies the communicative act library — twenty-two performatives (accept-proposal, agree, cancel, cfp, confirm, disconfirm, failure, inform, inform-if, inform-ref, not-understood, propagate, propose, proxy, query-if, query-ref, refuse, reject-proposal, request, request-when, request-whenever, subscribe) — each given by feasibility precondition (FP) and rational effect (RE) expressed in the FIPA Semantic Language (SL) over beliefs, intentions, and uncertainty. FIPA00067 specifies the message transport (HTTP, IIOP, WAP carriers; envelope and routing).

Two features make FIPA-ACL the canonical reference point — and the canonical negative example — for ACL semantics work. First, the direct lineage from Cohen and Levesque: the FP/RE structure of FIPA00037 is a streamlined adaptation of Cohen and Levesque 1995. The semantics of inform(p) is, modulo notation, exactly the Cohen–Levesque definition: the sender believes p, believes the receiver does not know p, and intends the receiver to come to believe p. The semantics of request mirrors attempt over a hearer action. Second, the unverifiability problem: precisely because the semantics is given in terms of sender and receiver mental states, no external observer can determine whether a message is FIPA-conformant. A platform that ships inform(p) in violation of its feasibility preconditions (e.g. the sender does not believe p, i.e. is lying) is indistinguishable on the wire from a platform that ships a conformant inform. This is the deficiency Singh 1998 names, Wooldridge formalises, and the commitment-based semantics tradition fixes.

For this vault, FIPA-ACL is the engineered artefact against which the public-semantics critique runs. The spec is well-engineered as a message format — the envelope, the protocol-id mechanism, the ontology / language slots are all sound — and the wire format itself has aged well. What has not aged well is the semantics by mental-state precondition: it is unverifiable, hostile to heterogeneous deployment, and incompatible with the public-semantics / commitment-based programme that CBCL inherits. The right reading is: keep the engineering, replace the semantics.

Key Ideas

Three-part suite: FIPA00061 (message structure), FIPA00037 (communicative act library), FIPA00067 (message transport).
Message structure: :sender, :receiver, :content, :language, :ontology, :protocol, :conversation-id, :reply-with, :in-reply-to, :reply-by, :performative. Standard envelope; the :content slot carries an arbitrary content-language expression interpreted by the :ontology.
Twenty-two performatives: from accept-proposal through subscribe, organised loosely into Searlean families (assertives, directives, commissives, declaratives). The set is small enough to remember and rich enough to cover most multi-agent interaction patterns.
Semantic Language (SL): FIPA’s formal language for FP/RE definitions; a modal logic over belief, uncertainty, intention, and action, descended from Cohen and Levesque.
Feasibility precondition / rational effect: each performative is defined by an FP (what must hold for the agent to perform the act in good faith) and an RE (what the agent intends to bring about). Both involve nested beliefs and intentions of sender and receiver.
Interaction protocols: FIPA also standardises a small set of interaction protocols (FIPA-Request, FIPA-Query, FIPA-ContractNet, FIPA-IteratedContractNet, FIPA-EnglishAuction, FIPA-DutchAuction, FIPA-Brokering, FIPA-Recruiting, FIPA-Subscribe, FIPA-Propose) — finite state machines over performatives that script common conversational patterns.
Unverifiability is intrinsic: the FP/RE conditions are stated over mental states; no external observer can check conformance without inspecting agent internals — a known design cost and the central target of the social-agency critique.

Connections

Conceptual Contribution

Claim: A standardised ACL can be built from a small set of performatives, each given by mental-state preconditions and intended effects in a modal logic, embedded in a standardised message envelope, with a standard library of interaction protocols. The result is the canonical industry ACL.
Mechanism: Three coordinated specs. FIPA00061 fixes the wire format (envelope parameters and message routing). FIPA00037 fixes the performative semantics in SL, with each of twenty-two performatives given by FP and RE in terms of belief, uncertainty, and intention nested over sender and receiver. FIPA00067 specifies the message transport. A small library of interaction protocols (FIPA-Request, FIPA-ContractNet, etc.) gives canonical conversational patterns as finite state machines over performatives.
Concepts introduced/used: FIPA Performative, Semantic Language (FIPA SL), Feasibility Precondition, Rational Effect, FIPA Interaction Protocol, ContractNet, ACL Message Envelope, Conversation ID.
Stance: standards specification suite / industry deliverable.
Relates to: Direct standardisation of Cohen and Levesque 1995 — the FIPA00037 semantics is essentially that paper’s framework with editorial smoothing. As the canonical engineering artefact of mentalistic ACL semantics, FIPA-ACL is the negative example for Singh 1998, Wooldridge, Yolum & Singh, Fornara & Colombetti, and the public-semantics tradition generally. CBCL reuses the engineering of FIPA-ACL (typed performative envelope, conversation-id, ontology slot, protocol-id) while replacing the semantics with publicly verifiable commitment-based meaning. The modern LLM-agent protocol generation (Model Context Protocol, Agent-to-Agent Protocol, LACP) has retreated from FIPA’s level of semantic ambition; the open question is whether that retreat will repeat the mentalistic mistake under a new guise (sycophantic JSON tool-calls) or learn from the FIPA experience.

Communicative Act Library

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Sincerity Condition

A precondition on speech acts requiring that the speaker actually hold the mental state the act expresses (e.g., belief for an assertion, intention for a promise). A persistent source of ACL verifiability problems.

In this vault

Joint Intentions

Cohen & Levesque’s theory of teamwork: joint persistent goals with mutual belief commitments.

In this vault

Mentalistic Semantics

ACL semantics in which each message commits the sender’s (and sometimes receiver’s) beliefs and intentions — powerful but unverifiable from outside.

In this vault

Rational Effect

In FIPA-ACL, the effect a sender of a communicative act intends to bring about in the recipient (e.g. that the hearer come to believe a proposition). Because it concerns private mental state it is unverifiable, and is the principal target of critiques that call for grounded or social semantics.

In this vault

Feasibility Precondition

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Attempt (Cohen-Levesque)

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Intention Is Choice with Commitment

Reference: Cohen, P.R. & Levesque, H.J. (1990). Artificial Intelligence 42(3): 213–261. Source file: cohen-levesque-intention-is-choice-with-commitment.pdf. URL

Summary

Cohen and Levesque formalise the “rational balance” that holds between an autonomous agent’s beliefs, goals, actions, and intentions. They define intention as a composite mental attitude: a persistent goal that the agent is committed to pursuing until it is achieved, known to be impossible, or no longer relevant. This yields a modal logic whose axioms capture Bratman’s three functional roles for intention — posing problems for means-end reasoning, acting as a screen of admissibility for future intentions, and prompting the agent to track (and re-try) the success of its actions.

The paper opens with the now-classic “Willie the robot” vignette (uncommitted, overcommitted, then homicidally committed), framing intention as what an agent must reason about to be both reliable and responsive. By relativising intentions to beliefs about another agent’s intentions the authors also sketch a theory of interpersonal commitment that anticipates speech-act and multi-agent communication semantics.

Key Ideas

Persistent goal (P-GOAL): a goal an agent will not drop until it is believed achieved, believed impossible, or its relevance condition fails.
Intention defined as a P-GOAL to have done an action while believing one is about to do it — closing Bratman’s gap between intending and acting intentionally.
Avoids the “side-effect problem”: agents don’t intend foreseen side-effects of their actions.
Mutual/relativised intentions as a foundation for interpersonal commitments and speech acts.
Desiderata list (beliefs, feasibility, non-futility, tracking) becomes a standard benchmark for intention logics.

Connections

Agent-Oriented Programming
Belief-Desire-Intention
BDI Logic
BDI Architecture
Joint Intentions
Commitment
Mental State
Rational Action Semantics
Speech Act Theory
Intentional Stance
Flexible Protocol Specification and Execution
A Commitment-Based Approach to Agent Communication
Communicative Actions for Artificial Agents - Cohen Levesque — the 1995 ICMAS sequel that turns the 1990 framework into an explicit speech-act / ACL semantics; direct ancestor of FIPA-ACL.
FIPA-ACL Specifications
Mentalistic Semantics
ACL Rethinking Principles — Singh’s critique of the BDI-based ACL semantics built on this foundation.

Conceptual Contribution

Claim: Intention is not a primitive mental state but a choice with commitment — a goal plus a meta-policy for when to drop it.
Mechanism: Modal logic over beliefs and goals plus a temporal operator for persistence; intention defined compositionally so its functional roles (planning, filtering, tracking) are theorems rather than axioms.
Concepts introduced/used: Persistent Goal, Commitment, Rational Balance, Mental State, Nested Beliefs, Joint Intentions.
Stance: foundational/formal.
Relates to: Shoham’s Agent-Oriented Programming cites this paper as the prime candidate for grounding AOP’s mental-state semantics; Shoham deliberately chooses a simpler obligation/commitment primitive for AGENT-0 but frames C&L as the rigorous theory AOP languages should eventually implement. The paper also underwrites FIPA-style Mentalistic Semantics and Rational Action Semantics for ACLs.

Tags

Semantics and Conversations for an ACL

Semantics and Conversations for an Agent Communication Language

Reference: Yannis Labrou and Tim Finin (1998). In Readings in Agents (Huhns & Singh eds., Morgan Kaufmann), reprinted from IJCAI-97. Source file: labrou-finin-1998.pdf. URL

Summary

Labrou and Finin supply the missing formal semantics for KQML. They treat KQML performatives as speech acts and, drawing on Searle and Vanderveken, describe each reserved performative (tell, ask-if, advertise, sorry, broker-one, …) by its preconditions, postconditions, and completion conditions over the cognitive states (BEL, KNOW, WANT, INT) of sender and receiver. On top of this performative-level semantics they add a conversation policy layer: a Definite Clause Grammar specifying legal sequences of performatives (conversations), giving KQML a two-tier account of meaning — individual acts plus interaction protocols.

This is the canonical mentalistic semantics that ACL Rethinking Principles critiques: KQML’s meaning is defined by what the agents are supposed to believe, know, and intend before and after sending each message, which is exactly the private, unverifiable mental-state grounding Singh objects to.

Key Ideas

KQML performatives carry illocutionary force; their meaning is given by speech-act-style preconditions and postconditions over agent mental states.
Four primitive mental-state operators: BEL(A,X), KNOW(A,X), WANT(A,X), INT(A,X); conjunctions and negations permitted but disjunction forbidden inside BEL/KNOW/WANT/INT.
Each performative specifies: intuitive meaning, content description, Pre(A)/Pre(B) preconditions, Post(A)/Post(B) postconditions, Completion condition, and an expected response performative.
advertise is analysed as a commissive — the sender commits to being able to process a later performative of the advertised type; tell as assertive; ask-if as directive.
Conversation policies: legal message sequences expressed as a DCG so that agents can plan and recognise multi-step exchanges (register-then-advertise-then-ask, broker patterns, etc.).
Negation of a mental-state expression means “not provable” from the agent’s knowledge base — making the semantics relative to the particular agent’s reasoner.

Connections

Conceptual Contribution

Claim: An Agent Communication Language acquires meaning at two layers — (1) per-performative speech-act semantics expressed as pre/post-conditions over the sender’s and receiver’s beliefs, knowledge, wants, and intentions, and (2) conversation policies expressed as a formal grammar over sequences of performatives — and this combination suffices to specify KQML.
Mechanism: Adopts Austin/Searle/Vanderveken speech-act categories, introduces the BEL/KNOW/WANT/INT operators, writes out pre/post/completion schemas for five reserved performatives (advertise, ask-if, tell, sorry, broker-one), and layers a Definite Clause Grammar to compose them into conversations.
Concepts introduced/used: Mentalistic Semantics, Performatives, Illocutionary Force, Conversation Policies, Preconditions and Postconditions, Commissives
Stance: constructive / foundational
Relates to: Direct target of the ACL Rethinking Principles critique — Singh names this mental-state grounding as the reason KQML compliance cannot be verified. Supplies the machinery later reused by FIPA-ACL and problematised by Verifiable Semantics for ACLs and Commitment-based Semantics.

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Verifiable Semantics for ACLs

Verifiable Semantics for Agent Communication Languages

Reference: Michael Wooldridge (1998). ICMAS-98 (International Conference on Multi-Agent Systems). Source file: icmas98.pdf. URL

Summary

Wooldridge tackles a central problem for ACL standardization: how can an external observer verify that an agent conforms to an ACL’s semantics when semantics are expressed in modal BDI logic (beliefs, desires, intentions)? He formalizes an agent communication framework as a tuple containing agent programs, local states, a communication language, a semantic language, and interpretation functions, and defines precisely what it means for a framework to be verifiable: whether one can decide, from program text alone, that the semantic conditions for a sent message are satisfied.

He shows that KQML and FIPA-97 ACL, which define the “sincerity condition” for an inform act using multi-modal quantified logics like SL, are not practically verifiable — deciding whether an agent program really believes what it says requires checking undecidable properties. In contrast, he gives two example frameworks with verifiable (even co-NP-complete) semantics by grounding meaning in program states rather than unobservable mental attitudes. The paper’s upshot: practical ACL conformance testing requires public, state-based semantics.

Key Ideas

Formal agent communication framework as a 2n+4 tuple.
Verifiability = decidability of semantic conformance from program text.
KQML and FIPA-97 semantics (SL modal logic) are not practically verifiable.
Grounding semantics in program states yields co-NP-complete verifiability.
Motivates social/public commitment-based ACL semantics.

Connections

KQML
FIPA-ACL
Speech Act Theory
Agent Communication Languages
Verifiable Semantics
Public Semantics
Commitment-based Semantics
Mental State
Mentalistic Semantics
BDI
CBCL - Safe Self-Extending Agent Communication — O’Connor 2026: a verifiable ACL grounded in DCFL grammars and Lean-checked safety invariants, answering Wooldridge’s challenge in the LLM-agent era.

Conceptual Contribution

Claim: An ACL standard is only useful if one can check whether an implementation respects it; existing ACLs (KQML, FIPA-97) whose semantics are given in multi-modal BDI logics are not practically verifiable, so ACL semantics should instead be grounded in program states.
Mechanism: Formalises an agent communication framework as a (2n+4)-tuple of agent programs, local states, communication language L_C, semantic language L_S, and interpretations; defines verifiability as decidability (in polynomial time) of whether an agent program respects a message’s semantic precondition; shows FIPA’s SL semantics undecidable; constructs two verifiable example frameworks (classical propositional logic, grounded propositional epistemic logic) with co-NP-complete verification.
Concepts introduced/used: Verifiable Semantics, Agent Communication Framework, Sincerity Condition, Grounded Semantics, Program Semantics, Model Checking, BDI Logic, Mentalistic Semantics
Stance: formal-semantic / critique
Relates to: Formal companion to ACL Rethinking Principles — Singh’s social-agency argument becomes Wooldridge’s verifiability theorem. Undermines the semantic ambitions of KQML Overview and FIPA-ACL; motivates commitment-based approaches such as Agent Communication And Institutional Reality and the program-grounded framework in Foundations Of Illocutionary Logic.

Tags

Agent Communication Languages - Rethinking the Principles

Agent Communication Languages: Rethinking the Principles

Reference: Singh, M. P. (1998). IEEE Computer (December 1998). Source file: singh-acl.pdf. URL

Summary

Singh argues that mainstream ACLs like KQML and FIPA/Arcol are built on an untenable mentalistic semantics — grounding message meaning in the sender’s beliefs and intentions — which cannot be verified from the outside and therefore cannot serve as a compliance standard. For true interoperability in heterogeneous multi-agent systems, he proposes shifting to a social agency model in which ACL semantics is defined in terms of public commitments, roles, and conventions rather than private mental states.

The paper maps the design space of ACLs along phisssspective (private/public), type of meaning (personal/conventional), basis (semantic/pragmatic), context (fixed/flexible), coverage (of communicative acts), and construction autonomy (design/execution). It motivates “societies” of agents with published protocols, where compliance becomes testable and dialects can usefully coexist. The move from mental to social semantics underpins later work on commitment-based protocols.

Key Ideas

Mentalistic ACL semantics is non-verifiables => poor basis for standards.
Social agency: commitments, roles, conventions as public meaning.
Design/execution autonomy orthogonal and both important.
Dialects are OK; idiolects are not.
Protocols as flexible specifications, not fixed FSMs.

Connections

Agent Communication Languages
FIPA-ACL
FIPA-ACL Specifications
KQML
Speech Act Theory
Commitment-based Semantics
Mentalistic Semantics
Public Semantics
Verifiable Semantics
Interaction Protocols
Conversation Policy
Multi-Agent Systems
Communicative Actions for Artificial Agents - Cohen Levesque — the mentalistic high-water mark this paper critiques
An Ontology for Commitments in Multiagent Systems - Singh — Singh’s own formal sequel: four-place commitment ontology
Articulating Reasons - Brandom — philosophical underwriting of Public Semantics
Making It Explicit - Brandom
Jones-Sergot Normative Systems — Counts-As Relation / institutional grounding
CBCL - Safe Self-Extending Agent Communication — O’Connor 2026 contemporary realisation

Conceptual Contribution

Claim: Mentalistic ACL semantics (KQML, FIPA/ARCOL) cannot ground interoperability because compliance with sincerity and belief conditions is externally unverifiable; ACLs should be rebuilt on a social semantics of public commitments, roles and conventions.
Mechanism: Singh maps the ACL design space along six axes — perspective (private/public), meaning type (personal/conventional), basis (semantic/pragmatic), context (fixed/flexible), coverage (communicative-act repertoire), and construction autonomy (design-time vs. run-time). He uses this scheme to argue that FIPA/KQML occupy an untenable region, and sketches a social-agency alternative in which agents belong to “societies” with published protocols, commitments are first-class, and dialects (but not idiolects) are tolerated.
Concepts introduced/used: Social Agency, Commitment-Based Semantics, Mentalistic Semantics, Conversation Policy, Dialect vs Idiolect, Design Autonomy, Execution Autonomy, ACL Verifiability
Stance: critique
Relates to: Directly targets the mentalistic stance of Agent-Oriented Programming, KQML as an Agent Communication Language, and FIPA-ACL; its social-semantic programme is operationalised by An Interaction-oriented Agent Framework for Open Environments (commitment-based Mercurio/JaCaMo) and cited approvingly by the surveys The State of the Art in Agent Communication Languages and Trends in Agent Communication Language.

Tags

Agent Communication Languages

A concept hub for agent communication languages (ACLs): languages whose speech acts let software agents exchange beliefs, goals, and commitments.

Canonical Languages

KQML — original knowledge-query language
FIPA-ACL — standardised successor

Surveys & Principles

The State of the Art in Agent Communication Languages
Trends in Agent Communication Language
ACL Rethinking Principles — Singh, mental vs. social semantics
Agent Communication Languages - Rethinking the Principles
A Common Ontology Of ACLs
Toward Automated Evolution of ACLs
Towards Automating the Evolution of Linguistic Competence

Semantics

Conversations & Protocols

Domain instances

Common Business Communication Language — McCarthy 1975/1982
CBCL - Safe Self-Extending Agent Communication — O’Connor 2026 (LangSec ’26): contemporary Lean-verified DCFL-bounded ACL realising McCarthy’s CBCL vision

KQML as an Agent Communication Language

Reference: Tim Finin, Richard Fritzson, Don McKay, and Robin McEntire (1994). CIKM ’94 (Proceedings of the Third International Conference on Information and Knowledge Management). Source file: 191246.191322.pdf. URL

Summary

Foundational paper on the Knowledge Query and Manipulation Language (KQML), developed under the ARPA Knowledge Sharing Effort. KQML is both a message format and a message-handling protocol for run-time knowledge sharing among intelligent agents. It builds on speech-act theory: each message (a performative) carries an illocutionary force (ask, tell, subscribe, advertise, recommend, broker, recruit, etc.) atop a content language (often KIF) and an ontology reference.

The paper describes the three-layer structure (content / message / communication), facilitator agents that provide matchmaking, brokering and content-based routing, and implementations including routers, facilitators, and KRIL interface libraries. KQML became the reference point against which later ACLs (notably FIPA-ACL) were designed.

Key Ideas

Performatives as speech-act-inspired message types
Separation of content language, message layer, and transport
Facilitators for advertise/subscribe, brokering, recruitment, routing
Reserved performatives: ask-if/ask-all, tell, stream-all, subscribe, monitor, advertise, recruit
KIF + ontologies as the assumed content layer

Connections

Conceptual Contribution

Claim: Interoperable knowledge sharing among heterogeneous intelligent agents requires a three-layer communication language (content / message / communication) whose message layer is built from speech-act-inspired performatives, and whose runtime infrastructure provides facilitator agents for matchmaking and brokering.
Mechanism: Specify ~30 reserved performatives (ask-if, tell, subscribe, advertise, recruit, broker-one, …) that wrap a content expression (typically KIF) with an ontology reference and transport metadata; implement via routers, facilitators, and per-application KRIL interface libraries; demonstrate advertise/subscribe, content-based routing, and recruitment patterns.
Concepts introduced/used: KQML, Performatives, Speech Act Theory, Facilitators, Facilitator Agents, Mentalistic Semantics, KIF, Ontologies, Agent Communication Languages, Conversation Policy, Interaction Protocols
Stance: engineering / standard-proposal
Relates to: Foundational reference against which FIPA-ACL, A Common Ontology Of ACLs, ACL Rethinking Principles, and Agent Communication Languages - Rethinking the Principles argue (over mentalistic vs commitment-based semantics). Performatives-as-protocol anticipates Agora’s Protocol Documents in A Scalable Communication Protocol for Networks of LLMs and the MCP/A2A/ANP layer of modern LLM agents (Model Context Protocol, Agent-to-Agent Protocol, Agent Network Protocol).

Tags

KQML Overview

An Overview of KQML: A Knowledge Query and Manipulation Language

Reference: KQML Advisory Group — Tim Finin, Don McKay, Rich Fritzson (and Hans Chalupsky, Stuart Shapiro, Gio Wiederhold) (1992/1993). Technical report, DARPA Knowledge Sharing Effort. Source file: kqmloverview.pdf. URL

Summary

This foundational technical report introduces KQML, the language and protocol designed under the DARPA-sponsored Knowledge Sharing Effort to enable interoperability among heterogeneous intelligent agents and knowledge-based systems. It identifies the canonical module types — End User Applications (EUAs), Knowledge-Based Systems (KBs), Knowledge Base Repositories (KBRs), Databases (DBs), and Active Sensors (ASs) — and enumerates the fifteen possible interfaces between them, selecting KB-to-KB knowledge interchange as the central target.

KQML is organized as three layers: a content layer (domain content in KIF or other logic), a message layer (performatives like tell, ask-one, subscribe, advertise, register), and a communication layer (sender, receiver, reply-ids, transport). The report details performatives, facilitators/routers (SKTP), ontology/topic matching, and a Prolog-based implementation. It set the vocabulary and architectural template for nearly all subsequent agent-communication work.

Key Ideas

Three-layer design: content, message, communication.
Performatives as named speech-act-like primitives (tell, ask, subscribe, advertise).
Facilitators/mediators (SKTP) for routing and knowledge-based-service discovery.
Module taxonomy: EUA, KB, KBR, DB, AS.
Separation of content language (KIF) from communication language (KQML).

Connections

KQML
FIPA-ACL
Agent Communication Languages
Ontologies
Speech Act Theory
Performatives
Facilitators
KQML Language And Protocol — journal companion
KQML as an Agent Communication Language — tutorial companion
KQML - A Language And Protocol For Knowledge And Information Exchange — 1994 workshop original
KIF
Mentalistic Semantics
Conceptualization

Conceptual Contribution

Claim: Large heterogeneous knowledge-based systems need a standard high-level language and protocol for interchange that separates domain content (ontologies/KIF) from communicative intent (performatives) and from transport — KQML provides this missing middle layer.
Mechanism: Defines module taxonomy (EUA, KB, KBR, DB, AS) and their 15 interfaces; proposes KQML’s three-layer architecture (content / message / communication); specifies performatives (tell, ask-one/all, stream, subscribe, advertise, register, broker, recruit, recommend) inspired by speech acts; specifies SKTP (facilitator) protocol for routing, ontology matching, and service discovery; gives a Prolog reference implementation.
Concepts introduced/used: KQML, Performatives, Facilitator, SKTP, Content Language, KIF, Knowledge Sharing Effort, Ontology Matching, Speech Acts
Stance: engineering / foundational
Relates to: The language critiqued in ACL Rethinking Principles and Verifiable Semantics for ACLs for its mentalistic informal semantics; its performatives are inherited by FIPA-ACL and the conversation work in Coordinating Agents Using ACL Conversations; its ontology-sharing aspirations are addressed by Ontolingua Portable Ontology Specifications.

Tags

KQML

Knowledge Query and Manipulation Language — one of the first ACLs, developed in the early 1990s by the ARPA Knowledge Sharing Effort. Performative-based, separating content language from communication.

Primary sources

Agent Communication Languages
FIPA-ACL — the standardised successor
Speech Act Theory
Ontolingua Portable Ontology Specifications — companion Knowledge Sharing Effort project
A Common Ontology Of ACLs
Verifiable Semantics for ACLs
CBCL - Safe Self-Extending Agent Communication — modern DCFL-bounded ACL with the same performative/extensibility ambitions but formal safety guarantees

FIPA-ACL

The Foundation for Intelligent Physical Agents Agent Communication Language — a standardised successor to KQML, defining performatives with mentalistic semantics (beliefs/intentions of sender and receiver).

Primary source

FIPA-ACL Specifications — the canonical standards documents (FIPA00037 Communicative Act Library, FIPA00061 Message Structure)
Communicative Actions for Artificial Agents - Cohen Levesque — Cohen & Levesque 1995, the direct semantic ancestor

Discussed in

Agent Communication Languages
Speech Act Theory
Multi-Agent Systems
Mentalistic Semantics
Public Semantics
Commitment-based Semantics
An Ontology for Commitments in Multiagent Systems - Singh
CBCL - Safe Self-Extending Agent Communication — DCFL-bounded ACL with public-commitment semantics, addressing the unverifiability of FIPA-ACL’s mentalistic SL semantics

Logic and Conversation

Reference: Grice, H. P. (1975). In P. Cole & J. L. Morgan (Eds.), Syntax and Semantics, Vol. 3: Speech Acts, pp. 41–58. Academic Press. (Originally delivered as the 1967 William James Lectures at Harvard.) Source file: grice_logic_and_conversation.pdf. URL

Summary

Grice’s foundational paper introduces the theory of conversational implicature: the mechanism by which speakers convey more than they literally say. Starting from the divergences formalists find between natural-language connectives (and, or, if, not, all, some) and their formal analogues, Grice argues the divergences do not show natural language is defective; rather, they arise from principles governing rational cooperative exchange, not from logical form.

At the centre is the Cooperative Principle: “Make your conversational contribution such as is required, at the stage at which it occurs, by the accepted purpose or direction of the talk exchange in which you are engaged.” The principle decomposes into four categories of maxims — Quantity (be as informative as required, no more), Quality (try to make your contribution true), Relation (be relevant), and Manner (be perspicuous). Speakers exploit these maxims — by apparently flouting them while the Cooperative Principle remains in force — to generate conversational implicatures that the hearer can calculate. The paper distinguishes what is said from what is implicated, and conventional from conversational implicatures, establishing the framework in which pragmatics has operated ever since. Its picture of communication as rational, cooperative, defeasible inference over an idealised shared purpose became a touchstone for ACL design, HCI dialogue systems, and the pragmatics of LLM prompting.

Key Ideas

What is said vs. what is implicated.
Conventional vs. conversational implicature.
Cooperative Principle as constitutive of rational discourse.
Four maxim categories: Quantity, Quality, Relation, Manner.
Implicatures arise from (apparent) maxim-flouting under the CP.
Implicatures are calculable, cancellable, non-detachable.
Natural-language/formal-logic divergences need not reflect semantic defect.

Connections

Conceptual Contribution

Claim: Successful communication rests on a presumed Cooperative Principle and its four categories of maxims; apparent violations of the maxims, against the background of presumed cooperation, generate implicatures — inferences about speaker meaning that go beyond literal content.
Mechanism: Grice frames discourse as goal-directed rational cooperation; derives the Cooperative Principle as a rationality constraint on contributions; distinguishes its maxims by Kantian category; shows that a speaker who says p while flouting a maxim (e.g., irrelevantly, uninformatively, or obscurely) signals that a further proposition q must be inferred to restore the presumption of cooperation — q is then conversationally implicated. Implicatures are calculable from the maxims plus context, cancellable without contradiction, and non-detachable from what is said.
Concepts introduced/used: Cooperative Principle, Conversational Implicature, Conventional Implicature, Gricean Maxims, Speaker Meaning, What Is Said
Stance: philosophical/pragmatic theory
Relates to: Complements the illocutionary classification of A Taxonomy of Illocutionary Acts by supplying a theory of pragmatic enrichment; informs the semantic/pragmatic layer distinctions in Agent Communication Languages and critiques of mentalistic ACL semantics in Agent Communication Languages - Rethinking the Principles; underpins the rational-speaker assumptions implicit in prompt engineering and LLM Agents.

Tags

Foundations Of Illocutionary Logic

Foundations of Illocutionary Logic

Reference: Searle & Vanderveken (1985). Cambridge University Press. Source file: 5F9BF68C-E1C8-11EE-931A-C444DB61CCB4.pdf. URL

Summary

Searle and Vanderveken construct a formalized logic of speech acts, filling the gap between philosophy of language and formal logic. The book recursively defines the space of illocutionary forces from five primitives (assertive, commissive, directive, declarative, expressive) via seven components of illocutionary force (illocutionary point, mode of achievement, propositional-content conditions, preparatory conditions, sincerity conditions, degree of strength, direction of fit).

It develops axiomatic propositional illocutionary logic, laws of illocutionary entailment, commitment, negation, conjunction, and conditionalization, and closes with a semantic analysis of over a hundred English performative verbs. The work is foundational for agent communication languages because it gives a rigorous semantics to the performatives (inform, request, promise, declare, etc.) later adopted by KQML and FIPA-ACL.

Key Ideas

Five illocutionary points: assertive, commissive, directive, declarative, expressive.
Seven components of illocutionary force.
Direction of fit: word-to-world vs world-to-word.
Formal calculus of success conditions and illocutionary entailment.
Semantic definitions of English performative verbs.

Connections

Conceptual Contribution

Claim: The space of possible speech acts is generated recursively from five illocutionary points and seven components of illocutionary force, and admits a genuine formal logic of success and entailment.
Mechanism: Axiomatic propositional illocutionary logic: laws of illocutionary entailment, commitment, negation, conjunction, and conditionalisation; closes with semantic definitions of over a hundred English performative verbs.
Concepts introduced/used: Speech Act Theory, Performatives, Illocutionary Force, Direction of Fit, Sincerity Conditions, Preparatory Conditions, Commitment-based Semantics, Mental State, Mentalistic Semantics
Stance: foundational / formal-semantic
Relates to: Supplies the philosophical semantics imported by KQML Language And Protocol and FIPA-ACL, and re-examined publicly in Agent Communication And Institutional Reality and A Common Ontology Of ACLs.

Tags

Speech Acts - An Essay in the Philosophy of Language

Speech Acts: An Essay in the Philosophy of Language

Reference: John R. Searle (1969). Speech Acts: An Essay in the Philosophy of Language. Cambridge University Press. Source file: Searle 1969 - Speech Acts.pdf. URL

Summary

Searle’s foundational monograph gives speech-act theory its first systematic, philosophically defended treatment. Extending Austin’s How to Do Things with Words, it argues that the minimal unit of linguistic communication is neither the symbol nor the sentence but the production of the symbol in the performance of a speech act. Searle develops a constitutive-rule analysis of illocutionary acts, codifies the felicity conditions of paradigm acts (promising, referring, predicating, asserting), and uses the framework to attack the fact/value distinction, deriving “ought” from “is” via the institutional fact of promising.

The book introduces the now-canonical machinery that McCarthy’s Elephant 2000 - A Programming Language Based on Speech Acts imports as programming-language primitives: the force/content distinction F(p), propositional-content conditions, preparatory conditions, sincerity conditions, and essential conditions. It is also the direct ancestor of Foundations Of Illocutionary Logic, which formalises what Searle here develops discursively.

Key Ideas

Speech acts as the unit of meaning: producing a sentence under appropriate conditions is performing an illocutionary act; meaning reduces to a recursive theory of these acts.
Force vs. content F(p): every utterance factors into illocutionary force (assert, promise, request, …) and propositional content.
Constitutive rules: rules of the form “X counts as Y in context C” create institutional facts (promises, marriages) rather than merely regulating antecedent behaviour.
Felicity conditions for promising (canonical analysis): propositional-content, preparatory, sincerity, and essential conditions — the template every later ACL performative inherits.
Reference and predication as distinct speech acts, each with their own rules.
Institutional facts and the is/ought derivation via promising as a constitutive practice.

Connections

Elephant 2000 - A Programming Language Based on Speech Acts — McCarthy’s direct source for the speech-act vocabulary of Elephant
Foundations Of Illocutionary Logic — Searle & Vanderveken 1985, formalises the present book
Speech Act Theory
Speech Acts
Performatives
Illocutionary Force
Sincerity Conditions
Preparatory Conditions
Agent Communication And Institutional Reality
KQML
FIPA-ACL
Agent Communication Languages
Commitment-based Semantics

Conceptual Contribution

Claim: Linguistic communication is irreducibly act-theoretic: the minimal unit of meaning is the illocutionary act, analysable by constitutive rules and felicity conditions, and this analysis extends to reference, predication, and the generation of institutional facts.
Mechanism: Case studies of promising, referring, and asserting yield a recursive schema F(p) with four condition-types (propositional-content / preparatory / sincerity / essential). The schema is then redeployed to distinguish regulative from constitutive rules and to dissolve the classical is/ought problem by showing that uttering “I promise” institutionally constitutes an obligation.
Concepts introduced/used: Performatives, Illocutionary Force, Sincerity Conditions, Preparatory Conditions, Speech Act Theory, Institutional Reality, Commitment-based Semantics
Stance: foundational / philosophical
Relates to: Imported wholesale by Elephant 2000 - A Programming Language Based on Speech Acts as the philosophical basis for speech-act I/O; formalised by Foundations Of Illocutionary Logic; re-examined for multi-agent systems in Agent Communication And Institutional Reality and operationalised in KQML / FIPA-ACL performative sets. McCarthy explicitly departs from Searle by adopting a design stance on these primitives — see Abstract Performative.

Tags

How to Do Things with Words

Reference: Austin, J. L. (1962). How to Do Things with Words. The William James Lectures delivered at Harvard University in 1955. Oxford: Clarendon Press (ed. J. O. Urmson). Source file: austin-1962-how-to-do-things-with-words.pdf. Cited by Elephant 2000 - A Programming Language Based on Speech Acts (McCarthy 1989).

Summary

Austin’s posthumously edited William James Lectures are the founding text of speech-act theory. Austin begins by isolating a class of utterances - “performatives” (e.g. “I promise”, “I do”, “I name this ship”) - that do not describe or report but instead perform an action, and cannot be evaluated as true or false but only as happy or unhappy (felicitous or infelicitous). Through twelve lectures he progressively dissolves the performative/constative distinction in favour of a general theory in which every utterance performs a locutionary, illocutionary, and perlocutionary act. The taxonomy of illocutionary force (verdictives, exercitives, commissives, behabitives, expositives) directly anticipates Searle/Vanderveken’s Foundations Of Illocutionary Logic and the performative vocabulary of KQML and FIPA-ACL.

Key Ideas

Performative utterance: saying is doing. “I promise” is not a report of a promise - it is the promise.
Felicity conditions: instead of truth conditions, performatives succeed or fail by satisfying procedural, sincerity, and uptake conditions.
Locution / illocution / perlocution: three layers of every speech act - what is said, what is done in saying it, and what is achieved by saying it.
Five illocutionary classes (verdictives, exercitives, commissives, behabitives, expositives) - taxonomy later refined by Searle into five primitives.
Dissolution of the performative/constative boundary: assertion itself turns out to be a species of illocutionary act.

Connections

Conceptual Contribution

Claim: Many utterances are not descriptions that can be true or false but actions that are performed in the saying; and on closer inspection the descriptive/performative divide collapses, so every utterance is a layered act with illocutionary force.
Mechanism: Contrast between constative and performative utterances; introduction of felicity conditions (A.1-A.2, B.1-B.2, Gamma.1-Gamma.2 misfires and abuses); the tri-layer locution/illocution/perlocution analysis; provisional five-way classification of illocutionary verbs.
Concepts introduced/used: Performatives, Illocutionary Force, Felicity Conditions, Locutionary Act, Perlocutionary Act, Speech Act Theory
Stance: foundational / ordinary-language-philosophy
Relates to: Provides the raw speech-act ontology that Searle formalises in Speech Acts and that McCarthy imports in Elephant 2000 - A Programming Language Based on Speech Acts; the felicity-condition apparatus recurs under “feasibility” and “sincerity” preconditions in FIPA-ACL semantics and in Commitment-based Semantics.

Tags

#speech-acts #philosophy-of-language #foundational #austin #performatives

Speech Act Theory

Philosophy-of-language framework (Austin, Searle, Vanderveken) in which utterances perform actions (illocutionary acts) — the semantic backbone of most Agent Communication Languages.

Sources

Foundations Of Illocutionary Logic — Searle & Vanderveken
Three Models for the Description of Language — Chomsky, foundations
Agent Communication And Institutional Reality

Applied in

Lineage

graph TD
  A["Austin (1962)<br/>How to Do Things with Words"] --> A1[Locutionary]
  A --> A2[Illocutionary]
  A --> A3[Perlocutionary]
  A2 --> S["Searle (1969, 1975)<br/>Speech Acts · Taxonomy of Illocutionary Acts"]
  S --> S1[Assertives]
  S --> S2[Directives]
  S --> S3[Commissives]
  S --> S4[Expressives]
  S --> S5[Declarations]
  G["Grice (1975)<br/>Logic and Conversation"] -.cooperative principle.-> S
  S --> V["Searle & Vanderveken (1985)<br/>Foundations of Illocutionary Logic"]
  V --> M["McCarthy (1989)<br/>Elephant 2000"]
  V --> KQML[KQML performatives]
  V --> FIPA[FIPA-ACL performatives]
  M --> FIPA
  KQML --> ACL[[Agent Communication Languages]]
  FIPA --> ACL

Papers: How to Do Things with Words · Speech Acts - An Essay in the Philosophy of Language · A Taxonomy of Illocutionary Acts · Logic and Conversation · Foundations Of Illocutionary Logic · Elephant 2000 - A Programming Language Based on Speech Acts

Persistent Goal

Cohen-Levesque: a goal the agent is committed to until it is achieved, becomes impossible, or its reason disappears — the key modal operator behind their intention-as-commitment definition.

In this vault

BDI Logic

A family of multimodal logics (Rao & Georgeff, Cohen & Levesque) that formalise the attitudes of Belief, Desire and Intention, giving axioms for their interaction over branching time. BDI logic underpins mentalistic semantics for agent communication languages.

In this vault

Belief-Desire-Intention

Alternative spelling of the BDI agent architecture; see BDI for the canonical entry.

In this vault

Rational Action Semantics

Cohen-Levesque-style ACL semantics in which each speech act has a rational effect deducible from the sender’s beliefs and goals — formal but famously unverifiable.

In this vault

Cohen and Levesque

Philip R. Cohen and Hector J. Levesque, whose joint and individual work in the 1980s–1990s formalised intention, joint intention, and the rational-balance constraints on BDI-style agents. Their 1990 paper Intention Is Choice with Commitment (AIJ 42) is the canonical formal model of intention as a persistent goal — a commitment to maintain a goal until it is believed achieved, believed unachievable, or its motivating reason dissolves. Cohen & Levesque (1991) Teamwork extends the analysis to joint action and joint intentions in multi-agent settings.