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 #commitments #protocol-specification #fsm-compilation #verifiability #foundational #social-agency

Backlinks

Linked Pages

Pact - A Choreographic Language for Agentic Ecosystems

Pact: A Choreographic Language for Agentic Ecosystems

Reference: Gopinathan, K., Feser, J., Naim, M., Tavares, Z. & Bingham, E. (2026). 2nd International Workshop on Choreographic Programming (CP 2026), Boulder, CO, June 15–19. arXiv:2605.03143v1 [cs.PL], 4 May 2026 (talk paper). Basis Research Institute. URL

Summary

Gopinathan et al. extend Choreographic Programming to the open-systems setting where participants are self-interested and may not faithfully execute a protocol. Choreographies (Montesi 2023; Bates et al. 2025) give correct-by-construction, deadlock-free distributed protocols by writing one global program that is mechanically projected to local endpoints, but they assume cooperative participants — they cannot answer why an autonomous agent should follow the projected protocol. Pact answers that question by adding three operators to a core choreographic calculus: agent.choose(τ) for explicit strategic non-determinism, agent.values(x) for declared utility dependencies, and world.choose(τ) for exogenous “nature” variables that capture each agent’s priors over the environment. Every Pact program then maps unambiguously to a formal extensive-form game.

The headline analysis is a decision-policy solver built on the Memo Programming Language (Chandra et al. 2025), a probabilistic-programming DSL for cognitive theory-of-mind models. From the projected Pact program a memo model is constructed in which each role recursively simulates the other to depth ℓ; running inference yields a level-ℓ bounded-rational policy mapping observations to choices. Applied to the canonical book-seller choreography the solver recreates Akerlof’s Market for Lemons: at depth 0 the buyer naïvely treats price as a signal of quality and the seller exploits this; as ℓ grows the acceptance probability flattens. The implementation is an embedded Python DSL on top of the Effectful algebraic-effects library, with endpoint projection realised as effect handlers. The paper is positioned as preliminary work; next steps named are formalising the semantics, proving correctness of projection-to-game, and adding incentive-compatibility / equilibrium / mechanism-design analyses.

Key Ideas

Choreography + game theory: a global protocol gets three game-theoretic operators (choice, value, nature) so that endpoint projection produces both a runnable program and a formal game.
values as type signature, not utility: declarations name the variables that influence an agent’s payoff but not the function — utilities are private and adversarially incentive-incompatible to disclose. The role of values is to constrain which protocols are mutually negotiable.
Theory-of-mind solver via memo: bounded-rational level-ℓ recursion over agent models, with the recursion bottoming out at naïve priors at ℓ = 0.
Lemons re-derived from a choreography: information asymmetry over an exogenous book.quality variable is enough to reproduce Akerlof’s unravelling result on the bookseller protocol.
Algebraic-effects implementation: endpoint projection implemented as effect handlers in Python (effectful); choreography is a single program that runs differently depending on which handler (Endpoint Projection) is installed.
Motivation framed against LLM agent failure modes: prompt injection, sycophancy, and coercion of LLM agents are cited as the reasons untrusted-counterpart coordination needs formal protocol artefacts rather than free-form natural-language negotiation.

Connections

Conceptual Contribution

Claim: Choreographic protocols for autonomous-agent ecosystems should make agent strategy first-class — explicit choices, declared utility dependencies, and exogenous priors — so that every protocol corresponds to a formal game and can be analysed for whether self-interested agents will participate.
Mechanism: Three new constructs added to a core choreographic calculus (agent.choose, agent.values, world.choose); a structural map from Pact programs to extensive-form games; a level-ℓ bounded-rational decision-policy solver built by translating the projected program into a Memo Programming Language theory-of-mind model and running probabilistic inference over it; an embedded-DSL implementation in Python via algebraic effects realising endpoint projection.
Concepts introduced/used: Choreographic Programming, Endpoint Projection, Theory of Mind, Memo Programming Language, Bounded Rationality, Market for Lemons, Mechanism Design, Algebraic Effects, Negotiation, Game-Theoretic Trust, Mentalistic Semantics
Stance: position / preliminary engineering (CP 2026 workshop talk paper)
Relates to: A contemporary LLM-era restatement of the individual-rationality answer to “why follow a protocol?” first formalised by Deals Among Rational Agents (Rosenschein & Genesereth 1985) and lifted to mental attitudes by Intention Is Choice with Commitment (Cohen & Levesque 1990). The paper is structurally adjacent to — but does not engage — the entire commitment-protocol tradition: Flexible Protocol Specification and Execution (Yolum & Singh 2002) gives a global protocol semantics in the Event Calculus with explicit Create / Discharge / Cancel / Release / Assign / Delegate operations whose runs project to local agents in a way directly analogous to choreographic endpoint projection, and A Commitment-Based Approach to Agent Communication (Fornara & Colombetti 2004) gives an operational FSM semantics for the same primitives. ACL Rethinking Principles (Singh 1998) and Verifiable Semantics for ACLs (Wooldridge 1998) anticipate the central limitation: a semantics grounded in agent utilities and recursive belief models is unverifiable from message traces alone — the very failure modes the paper opens with (prompt injection, sycophancy, coercion) destabilise the priors and rationality assumptions the solver depends on. The Lemons demo, taken at face value, is an argument for institutional / commitment mechanisms (warranties, refund obligations, certification) of the kind Singh’s programme articulates rather than for theory-of-mind solving. The constructive synthesis the paper does not propose is to layer commitment operations onto the choreographic substrate so that protocols carry both a public, observable commitment trace (Singh-style verifiability) and a game-theoretic acceptability analysis (Pact-style strategic reasoning); choreographies are a particularly natural host because endpoint projection already gives the global-to-local move that Commitment Machines approximates by FSM compilation. On the LLM-agent side the paper’s diagnosis converges with Why AI Agents Communicate In Human Language (formal protocol artefacts beat free-form natural-language negotiation) and complements the standardisation argument of LLM Agent Communication Protocol Requires Urgent Standardization.

Tags

Endpoint Projection

The mechanical translation from a global choreographic program — which describes the joint behaviour of all participants — to a per-participant local program that, when run in parallel with the others, realises the choreography. Endpoint projection is the operation that makes Choreographic Programming practical: the global program is the source of truth, and projection to each role is a syntactic/semantic transformation that preserves the communication structure and (under standard well-formedness conditions) deadlock-freedom. Implementations differ in how role information is tracked — type-system roles (Choral, ChoRus), census polymorphism (Bates et al. 2025), or algebraic-effect handlers (Pact, Effectful) — but all share the global-to-local move that distinguishes choreographic from session-typed programming. The structural analogue in commitment-based protocol theory is Commitment Machines, which compiles a global commitment specification to per-role finite-state machines.

In this vault

Choreographic Programming
Structured Communication-Centred Programming for Web Services — origin of the Theorem of End-Point Projection
Multiparty Asynchronous Session Types — multiparty projection G ↾ p
Introduction to Choreographies
Session Types
Pact - A Choreographic Language for Agentic Ecosystems
Commitment Machines
Algebraic Effects

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

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

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

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

Event Calculus

A logic-based formalism (Kowalski & Sergot 1986; Shanahan’s planner formulation 2000) for reasoning about events that initiate and terminate fluents — properties whose truth value changes over time. Events are described by Initiates, Terminates, Happens, HoldsAt, Clipped, and Declipped predicates plus a small set of axioms.

In the agent-communication strand it is used to give an executable, planner-driven semantics to commitment-based protocols: each commitment is a fluent, each communicative act an event with Initiates/Terminates clauses, and protocol runs are abductively generated from initial- and goal-state descriptions.

In this vault

Flexible Protocol Specification and Execution

Flexible Protocol Specification and Execution: Applying Event Calculus Planning Using Commitments

Reference: Yolum, P. & Singh, M.P. (2002). Proceedings of the 1st International Joint Conference on Autonomous Agents and Multiagent Systems (AAMAS ’02), pp. 527–534. ACM, Bologna. Source file: yolum-singh-2002-flexible-protocol.pdf. URL

Summary

Yolum and Singh argue that finite-state-machine and Petri-net protocol formalisms over-constrain multi-agent interactions because they fix legal sequences of message tokens without regard to what those messages mean. They develop a commitment-based alternative in which each protocol action is reified as an operation on social commitments — Create, Discharge, Cancel, Release, Assign, Delegate — and the rules for how commitments evolve are formalised in a variant of the Event Calculus (Kowalski-Sergot, in Shanahan’s planner formulation). Base-level commitments C(x,y,p) and conditional commitments CC(x,y,p,q) become event-calculus fluents whose Initiates/Terminates clauses constitute the protocol specification.

The running example is the NetBill e-commerce protocol. Three reasoning postulates capture how a base-level commitment is discharged when its content holds, how a conditional commitment resolves into a base-level commitment when its precondition fires, and how CC is consumed when its consequent already holds. An abductive event-calculus planner (Shanahan) is then used to generate protocol runs from an initial state to a goal state, allowing agents to skip steps, reorder messages, or repair exceptions at runtime — provided every base-level commitment created during the run is eventually discharged. The result satisfies Singh’s three social-semantic desiderata: meaningful (content captured), verifiable (compliance checkable from public commitment trace), and declarative (specifies what each action achieves, not how to sequence actions).

Key Ideas

Commitment as fluent in event calculus: C(x,y,p) and CC(x,y,p,q) represented by the EC predicates Initiates, Terminates, HoldsAt, Happens, etc.
Six commitment operations (Create, Discharge, Cancel, Release, Assign, Delegate) compiled into Initiates/Terminates clauses.
Three postulates link content fluents to commitment fluents: discharging on content satisfaction, conditional-commitment resolution, and conditional consumption when consequent already true.
A protocol run is a sequence of Happens events; complete iff no base-level commitment is left holding — incomplete runs identify non-compliant agents.
Abductive planning (Shanahan) generates legal protocol runs from initial-state + goal-state descriptions, restoring autonomy/flexibility lost in FSM models.
Skipping steps and reordering (e.g. send-goods-before-accept) is supported because preconditions are over commitment state, not over a path through an FSM.
Permissions encoded via action preconditions; prohibitions encoded as commitments-not-to-bring-about.

Connections

Conceptual Contribution

Claim: Multi-agent protocols should be specified by the meaning of their actions — concretely, by how each action transforms the agents’ social commitments — rather than by legal token sequences; doing so simultaneously delivers meaningful, verifiable, and declarative semantics, and lets agents skip, reorder, or repair steps via runtime planning while still being held to their obligations.
Mechanism: Reify commitments as event-calculus fluents and define the six manipulation operations (Create/Discharge/Cancel/Release/Assign/Delegate) as Initiates/Terminates clauses; add three reasoning postulates governing base-level discharge and conditional-commitment resolution; use Shanahan’s abductive event-calculus planner to compute runs (sets of Happens clauses with a partial order) from initial states to goal states under the protocol’s preconditions; declare a run complete iff no base-level commitment is left holding, providing an objective compliance criterion.
Concepts introduced/used: Commitment, Conditional Commitment, Commitment-Based Protocol, Commitment-based Semantics, Event Calculus, Abductive Planning, Public Semantics, Verifiable Semantics, Conversation Protocols, Interaction Protocols, NetBill Protocol, Commitment Machines
Stance: formal-semantic / engineering
Relates to: Direct response to FSM- and Petri-net-based protocol traditions critiqued in ACL Rethinking Principles; supplies the operational machinery whose mentalistic counterpart (KQML/FIPA-SL) is shown unverifiable in Verifiable Semantics for ACLs. Companion to Singh’s social-agency programme and to the institutional-reality strand of Agent Communication And Institutional Reality. Conditional-commitment treatment derives from Colombetti’s earlier work and is contemporaneous with A Commitment-Based Approach to Agent Communication (Fornara & Colombetti AAMAS-02 / AAI-04), which gives a complementary object-oriented account of the same primitives (those authors note Yolum-Singh as the closest relative). Commitment-machine compilation to FSMs is the subject of the authors’ parallel ATAL-01 paper. Empire of mentalistic semantics from Intention Is Choice with Commitment is the foil — here intentions/persistence are not needed because the protocol semantics is exhausted by the public commitment trace.

Tags

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

Conversation Protocols

Stateful, multi-turn interaction patterns (Contract Net, auction, query) specified as a finite automaton, Petri net, or role-based dialogue over performatives. Promote tractable ACL use by constraining expected message sequences, and are the unit on which ACRE’s reasoning engine operates.

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NetBill Protocol

An e-commerce payment protocol (Sirbu, IEEE Spectrum 1997) in which a customer requests a quote, the merchant delivers (encrypted) goods after acceptance, the customer sends an electronic payment order, and the merchant returns a receipt that contains the decryption key. Used as the canonical worked example in Yolum & Singh’s commitment-based protocol-specification papers because its conditional payment-for-key structure exhibits the opportunities and exceptions that finite-state-machine protocol models cannot accommodate flexibly.

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Verifiable Semantics

ACL semantics whose conformance can be checked against observable agent program state — the key demand behind moving from mentalistic to public semantics.

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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

Social Commitment

A commitment treated as a public, social object — owned by the dyad of debtor and creditor and observable to third parties — rather than a private mental state of an individual agent. Social commitments are the central primitive of commitment-based ACL semantics: their lifecycle (created, conditional, active, fulfilled, violated, cancelled) is what an external observer monitors to verify protocol compliance. Castelfranchi 1995 is the foundational reference; Singh, Colombetti, Yolum, and Fornara give operational accounts.

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Conditional Commitment

A commitment of the form if condition Q is satisfied, then debtor x is committed to creditor y for content P — written CC(x, y, P, Q) (Yolum-Singh) or C(cc, x, y, P|Q) (Fornara-Colombetti). When Q resolves to true the conditional commitment becomes an active base-level commitment C(x, y, P); when Q resolves to false it is cancelled. Conditional commitments are the workhorse for negotiation, conditional promises, proposals, and bidding in commitment-based ACL protocols.

In this vault

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

Commitment-Based Protocol

An interaction protocol specified not by a fixed message sequence but by the social commitments agents create, discharge, cancel or delegate through their messages. This gives an objective, verifiable semantics that tolerates flexible enactment.

In this vault

Commitment Machines

Yolum & Singh’s (ATAL-01) protocol formalism: states and actions carry declarative meaning in terms of the participants’ commitments rather than being mere FSM tokens, and transitions are inferred from the logical consequences of applying an action’s effect to the current meaning. A complete commitment machine is sound-and-completely compilable to a deterministic FSM, combining the executability advantages of FSMs with the meaning-preserving semantics of commitment-based specification — agents that cannot reason logically can still follow the compiled FSM, while agents that can reason logically can plan novel paths to a final meaning. Structurally a direct analogue of Endpoint Projection in Choreographic Programming.

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Choreographic Programming

A programming paradigm in which a single global program describes the joint behaviour of all participants in a distributed protocol, and a mechanical endpoint projection derives the local program for each participant. Choreographic languages are designed so that well-typed choreographies are deadlock-free by construction — every send is matched by a corresponding recv in the projected counterpart. Originating in WS-CDL and formalised in the π-calculus / session-types community (Carbone, Honda, Yoshida), the paradigm has since been embedded in production languages (Choral for Java, ChoRus for Rust, HasChor for Haskell, Bates et al.’s census-polymorphic projection at PLDI 2025) and extended towards adversarial settings via cryptographic primitives (Sarkar & Russo; Veiga). Structurally adjacent to the Commitment-Based Protocol tradition: both specify protocols globally and project to local roles, but choreographic semantics is operational/communicational while commitment-based semantics is normative/social.

In this vault

Endpoint Projection
Structured Communication-Centred Programming for Web Services — Carbone, Honda & Yoshida ESOP 2007 / TOPLAS 2012, the foundational paper
Multiparty Asynchronous Session Types — Honda, Yoshida & Carbone POPL 2008, multiparty generalisation
Introduction to Choreographies — Montesi 2023 (Cambridge), the canonical textbook
On the Monitorability of Session Types — Bartolo Burlò, Francalanza & Scalas ECOOP 2021, runtime monitoring
Session Types
Pact - A Choreographic Language for Agentic Ecosystems
Commitment-Based Protocol
Commitment Machines
Flexible Protocol Specification and Execution
Algebraic Effects

Commitment

A public, directed obligation from one agent to another to bring about some condition; commitments serve as the social-semantic alternative to mentalistic ACL semantics and ground protocol correctness in observable state rather than private beliefs.

In this vault

A Common Ontology Of ACLs

A Common Ontology of Agent Communication Languages: Modeling Mental Attitudes and Social Commitments using Roles

Reference: Boella, Damiano, Hulstijn, van der Torre (2006). Applied Ontology 3(1-3). Source file: ao07b.pdf. URL

Summary

The authors propose a common ontology that bridges two dominant semantic traditions for Agent Communication Langua mental-attitude-based semantics (FIPA-ACL) and social-commitment-based semantics (Singh, Colombetti). The unifying device is the role: each agent plays role instances in dialogue sessions, and both beliefs/intentions and commitments are attributed to role instances rather than to private mental states, sidestepping the unverifiability problem.

They develop Role-SL, a BDI logic extended with roles and dialogue sessions, and show translation schemes from FIPA speech acts and from actioandopositional commitment semantics into this role-based ontology. The framework accommodates mixed dialogues (e.g., persuasion intertwined with negotiation) that neither tradition handles cleanly alone.

Key Ideas

Roles as first-class carriers of public mental attitudes.
Role-SL: extension of FIPA-SL with role instances and dialogue sessions.
Mappings from FIPA-ACL and commitment-based ACLs into one ontology.
Public beliefs/intentions sidestep mental-state unverifiability.
Distinguishes action commitments (request/propose) from propositional (assert/challenge).

Connections

Conceptual Contribution

Claim: Mental-attitude and social-commitment ACL semantics can be unified under a common ontology by attributing both to roles instantiated in dialogue sessions, rather than to private agent minds.
Mechanism: Extends FIPA-SL into Role-SL (BDI + roles + dialogue sessions); provides translation schemes from FIPA speech acts and from action/propositional commitment semantics; handles mixed dialogues (persuasion + negotiation).
Concepts introduced/used: Roles, BDI, Commitment-based Semantics, Mental Attitudes, Mentalistic Semantics, Public Semantics, Verifiable Semantics, Dialogue Sessions, FIPA-ACL, Speech Act Theory, Ontologies, Agent Communication Languages
Stance: formal-semantic
Relates to: Bridges the two traditions typified by FIPA-ACL (mentalist) and Agent Communication And Institutional Reality (commitment-based); uses ontology machinery catalogued in Handbook On Ontologies.

Tags

Agent Communication And Institutional Reality

Agent Communication and Institutional Reality

Reference: Fornara, Viganò, Colombetti (2005). Agent Communication II, LNAI 3396, Springer. Source file: 978-3-540-32258-0_1.pdf. URL

Summary

Fornara, Viganò, and Colombetti propose regarding an Agent Communication Language as a set of conventions acting on a fragment of institutional reality, defined within an artificial institution. They reformulate commitment-based ACL semantics so that all commonly used communicative act types reduce to a single basic type, declarations, within a Basic Institution that regulates the lifecycle of social commitments.

Special institutions (e.g., English Auctions) extend the Basic Institution with ontological and normative elements. The approach is notable for making the semantics of speech acts publicly verifiable and independent of agents’ mental states, while retaining a uniform formal account of institutional actions and counts-as relations.

Key Ideas

ACL messages are institutional actions governed by counts-as rules.
Basic Institution manages creation/update/cancellation of social commitments.
All speech act types reducible to declarations within the institution.
Special institutions layer domain norms and ontologies on top.
English Auction given as worked example.

Connections

Conceptual Contribution

Claim: An ACL is best understood as a set of conventions operating on institutional reality; all communicative act types reduce to declarations within a Basic Institution that governs the lifecycle of social commitments.
Mechanism: Defines artificial institutions with counts-as rules; models message effects as declarations creating/updating/cancelling commitments; layers domain norms in Special Institutions (English Auction worked example).
Concepts introduced/used: Commitment-based Semantics, Institutional Reality, Counts-as Rules, Declarations, Performatives, Speech Act Theory, Public Semantics, Verifiable Semantics, Mentalistic Semantics, Ontologies, FIPA-ACL, Multi-Agent Systems
Stance: formal-semantic
Relates to: Offers the publicly-verifiable alternative to mental-state semantics of FIPA-ACL, which A Common Ontology Of ACLs then unifies via roles; grounded philosophically in Foundations Of Illocutionary Logic.