BDI Agent Design (Móra et al.)

Skill ID: bdi-agent-design-mora
Version: 1.0
Author: Based on "BDI Models and Systems: Reducing the Gap" by Móra, Lopes, Viccari, and Coelho
Activation Triggers: BDI architecture, agent systems, intention reasoning, belief-desire-intention, operational semantics, agent deliberation, commitment mechanisms, rational agents

Description

Design and implement rational agent systems using the Beliefs-Desires-Intentions (BDI) paradigm with executable semantics. This skill bridges the theory-practice gap by using Extended Logic Programming with paraconsistent semantics as both formal specification AND reasoning engine.

When to Use This Skill

Load this skill when facing:

• Theory-practice gaps: Formal agent specifications that can't be executed, or implemented systems lacking formal grounding
• Commitment modeling: Designing how agents maintain intentions over time without perpetual re-deliberation
• Desire conflicts: Systems where goals naturally contradict and agents must choose rationally among competing objectives
• Deliberation control: Determining when agents should reconsider commitments vs. persist with current plans
• Belief revision: Handling contradictory information or discovering beliefs incompatible with intentions
• Practical rationality: Building agents that make "good enough" decisions with bounded computational resources

Decision Points

Core Architecture Choice

IF building theoretical specification OR formal verification required
├─ Use axiomatic modal/temporal BDI logics (Cohen & Levesque, Rao & Georgeff)
└─ Accept theory-implementation gap

IF building executable agent system
├─ Use Extended Logic Programming with operational semantics
└─ Formal specification IS the reasoning engine

Intention Revision Triggers

IF action completes/fails
├─ Remove completed intentions from commitment set
├─ Check if failure makes other intentions impossible
└─ Filter satisfied desires from candidate pool

IF deadline reached
├─ Remove expired intentions
├─ Re-evaluate previously delayed desires
└─ Trigger replanning for dependent actions

IF belief-intention contradiction detected
├─ IF abduction can find missing preconditions → revise beliefs
└─ IF intention truly impossible → abandon intention

IF higher-priority desire becomes feasible
├─ IF conflicts with current intentions → trigger deliberation
└─ IF compatible → adopt without disrupting commitments

IF no trigger condition met
└─ Maintain current intentions (commitment persistence)

Negation Strategy Selection

IF representing "agent actively believes/desires X is false"
└─ Use explicit negation: ¬P

IF querying "is there evidence for X?"
└─ Use negation-by-failure: not P

IF detecting conflicts between mental states
├─ Need explicit negation for: desire(P) ∧ desire(¬P)
└─ Negation-by-failure cannot detect this contradiction

Conflict Resolution Approach

IF desires directly contradict (P ∧ ¬P)
├─ Apply priority ordering
└─ Keep higher-priority desire, remove lower

IF desires have incompatible resource requirements
├─ Use abduction to test joint feasibility
├─ IF multiple consistent subsets exist → apply maximality preference
└─ IF no consistent subset → escalate to user/higher-level goal

IF paraconsistent contradiction detected
├─ Trigger minimal revision procedure
├─ Restore consistency through preference-guided removal
└─ Use contradiction as deliberation input, not error condition

Failure Modes

Modal Logic Without Proof Procedures

Detection: Elegant BDI specifications exist but implementation uses ad-hoc data structures with no resemblance to specification
Root Cause: Choosing specification formalisms that cannot execute
Fix: Use formalisms where specification IS executable (Extended Logic Programming) or commit to mechanized modal logic with runtime theorem proving

Negation Conflation

Detection: System uses only not P for both "unknown" and "actively false"; cannot represent negative intentions like "intend NOT to interrupt user"
Root Cause: Treating negation-by-failure as sufficient for all negative information
Fix: Use explicit negation ¬P for affirmative negative knowledge; reserve not P for closed-world queries

Perpetual Re-deliberation

Detection: Agent recalculates optimal intentions every cycle; never executes plans longer than one decision cycle; high CPU usage in deliberation
Root Cause: No commitment mechanism; treating all desires as immediate commands
Fix: Implement trigger-based revision with explicit commitment constraints; intentions persist between triggers

Contradiction Crashes

Detection: System enters undefined state or throws exceptions when desires conflict; requires pre-filtering desires for consistency
Root Cause: Classical logic semantics where contradictions make everything provable
Fix: Use paraconsistent semantics (WFSX) where contradictions are detectable signals triggering deliberation

Combinatorial Preference Explosion

Detection: System generates all possible consistent desire subsets then applies preference; exponential slowdown with desire set size
Root Cause: Treating preference as post-processing filter rather than search guidance
Fix: Integrate preference into revision procedure; guide search toward preferred revisions without enumerating all possibilities

Beliefs and Intentions in Separate Systems

Detection: Belief reasoner separate from intention manager; manual synchronization required; no integrated feasibility checking
Root Cause: Representing beliefs and intentions in independent systems with no unified semantics
Fix: Represent beliefs and intentions in the same logical framework (ELP); unified revision mechanisms enable integrated consistency checking and abductive reasoning

Worked Examples

Example 1: Belief-Intention Contradiction Resolution

Scenario: Household robot intends to serve_coffee but discovers coffee_maker_broken.

% Initial state
belief(coffee_maker_broken).
intention(serve_coffee).
action_precondition(serve_coffee, working_coffee_maker).

% Contradiction detection (paraconsistent semantics)
contradiction :- 
    intention(serve_coffee),
    belief(coffee_maker_broken),
    action_precondition(serve_coffee, working_coffee_maker),
    not belief(working_coffee_maker).

% Abductive feasibility check
missing_precondition(X) :-
    intention(A), action_precondition(A, X),
    not belief(X), not belief(¬X).

% Option 1: Abandon intention
revised_intentions_1([]) :- contradiction.

% Option 2: Abductive belief revision (find alternative)
revised_beliefs_2([belief(use_instant_coffee), belief(working_instant_dispenser)]) :-
    contradiction,
    alternative_action(serve_coffee, use_instant_coffee),
    abducible(working_instant_dispenser).

Decision Process: (1) Contradiction detected → trigger deliberation. (2) Check abductive alternatives → instant coffee possible. (3) Preference evaluation → satisfying desire preferred over abandoning. (4) Revise beliefs, maintain intention.

Novice Miss: Abandons intention immediately without checking alternatives
Expert Catch: Uses abduction to find feasible alternative means to same end

Example 2: Competing Desire Deliberation

Scenario: Personal assistant agent with conflicting scheduling desires.

desire(schedule_meeting(client_A, 2pm)).
desire(¬schedule_meeting(client_A, 2pm)).  % Explicit negation - active aversion
desire(schedule_workout(2pm)).

priority(schedule_meeting(client_A, 2pm), 8).
priority(schedule_workout(2pm), 6).

conflicts(schedule_meeting(client_A, 2pm), schedule_workout(2pm)) :- 
    same_time_slot(2pm, 2pm).

% Paraconsistent contradiction detection
find_contradictions([(desire(P), desire(¬P)) | Rest]) :-
    desire(P), desire(¬P), find_contradictions(Rest).

% Priority-based resolution
resolve_by_priority([(desire(P), desire(¬P))], [desire(P)]) :-
    priority(P, X), priority(¬P, Y), X > Y.

Decision Process: (1) Explicit negation detects desire(schedule_meeting) ∧ desire(¬schedule_meeting). (2) Priority resolution: meeting (8) beats ¬meeting. (3) Resource check: meeting conflicts with workout. (4) Adopt schedule_meeting(client_A, 2pm), reject others.

Novice Miss: Uses only negation-by-failure, missing the explicit aversion
Expert Catch: Recognizes explicit negative desires as different from mere absence

Example 3: Commitment Persistence Under Temptation

Scenario: Study assistant maintains focus intention despite social media desires.

committed_intention(study_mathematics, until(exam_complete)).
committed_intention(¬use_social_media, until(study_session_end)).

desire(check_facebook).
desire(browse_instagram).

conflicts_with_commitment(X) :-
    committed_intention(¬X, Until),
    \+ condition_met(Until).

trigger_deliberation :-
    (action_completed(_) ; deadline_reached(_) ; impossibility_detected(_)).

current_intentions(Result) :-
    \+ trigger_deliberation,
    findall(I, committed_intention(I, _), Result).

Decision Process: (1) New desires arise but no trigger condition met. (2) Commitment constraints block social media desires. (3) Study intentions persist without re-evaluation.

Novice Miss: Re-evaluates all desires, breaking commitment
Expert Catch: Commitment means NOT reconsidering unless specific triggers fire

Quality Gates

• Contradiction detection uses paraconsistent semantics (can detect P ∧ ¬P without system failure)
• Explicit negation distinguished from negation-by-failure (represents both "actively false" and "unknown")
• Commitment persistence prevents arbitrary re-deliberation (intentions persist unless trigger conditions met)
• Abductive feasibility checking available for intention adoption (detects missing preconditions before commitment)
• Trigger conditions explicitly specified for deliberation (action completion, deadlines, impossibility, higher-priority opportunities)
• Preference ordering integrated into revision procedure (guides search, doesn't post-filter all options)
• Beliefs and intentions represented in same logical framework (enables integrated consistency checking)
• Minimal revision procedures prefer smaller changes (stability over arbitrary change)
• Resource conflict detection prevents incompatible simultaneous intentions
• Deliberation termination criteria prevent infinite reconsideration loops

Reference Files

• diagrams/01_stateDiagram-v2_bdi_agent_mental_state_lifecyc.md — Mermaid state diagram showing belief acquisition, desire formation, consistency checks, and intention adoption cycles. Read when designing the mental state transitions of a BDI agent.

• diagrams/02_flowchart_deliberation_&_revision_proced.md — Decision tree for deliberation triggers (inconsistency, action failure, deadline, belief change) and conflict resolution paths. Read when implementing deliberation logic or choosing negation/paraconsistent strategies.

• diagrams/03_timeline_agent_execution_timeline_with_.md — Timeline showing action execution, trigger evaluation, and conditional deliberation phases. Read when modeling agent execution cycles and when deliberation should fire.

• references/abduction-as-intention-feasibility-check.md — How agents use abduction to verify intentions are achievable before commitment, avoiding impossible goals. Read when designing belief revision or intention filtering logic.

• references/computational-commitment-through-revision-constraints.md — Making commitment operational by filtering future intentions through revision constraints. Read when implementing intention persistence and preventing perpetual re-deliberation.

• references/desires-as-search-space-not-commands.md — Distinguishing desires (candidate goals) from intentions (committed goals) and structuring deliberation before commitment. Read when architecting goal-driven systems or designing desire-to-intention filtering.

• references/event-calculus-as-operational-time-and-action-model.md — Using event calculus for temporal reasoning in BDI agents (durative goals, action consequences, deadline detection). Read when adding time-dependent reasoning or deadline-triggered deliberation.

• references/preference-over-consistency-restoring-revisions.md — Encoding deliberation policy by ranking multiple conflict-resolution options. Read when multiple consistent subsets exist and agent must choose rationally among them.

• references/revision-mechanisms-as-non-monotonic-deliberation.md — How paraconsistent logic enables deliberation with contradictory desires before commitment. Read when handling conflicting goals or designing non-monotonic reasoning.

• references/triggers-and-attention-in-committed-agents.md — Balancing commitment persistence against responsiveness; when deliberation should be triggered. Read when tuning commitment strength or designing trigger conditions.

NOT-FOR Boundaries

This skill is NOT for:

• Pure theorem proving: For formal verification without execution, use modal BDI logics instead
• Reactive architectures: For stimulus-response systems without deliberation, use reactive-agent-patterns
• Multi-agent negotiation: For inter-agent protocols, use agent-communication-protocols
• Learning-based adaptation: For goal adaptation via ML, use reinforcement-learning-agents
• Real-time hard constraints: Where deliberation latency is unacceptable, use real-time-agent-scheduling
• Distributed consensus: For coordinating intentions across agents, use distributed-agent-coordination

Delegate when: agent must learn new goals → goal-learning-systems | agents must coordinate plans → multi-agent-planning | environment fully observable/deterministic → classical-planning-agents

Shibboleths: Recognizing Deep Understanding

Surface-level says: "BDI agents have beliefs, desires, and intentions as data structures" | "Commitment means intentions don't change" | "When desires conflict, pick the highest priority"

Deep internalization recognizes:

• "The formalism's operational semantics determines whether the theory-implementation gap exists": Asks "what's the proof procedure?" before "what's the axiomatization?"
• "Explicit negation enables conflict detection; negation-by-failure represents incomplete information": desire(¬P) (active aversion) is distinct from absence of desire(P) (indifference)
• "Paraconsistent semantics make contradictions productive inputs to deliberation": Conflicting desires are the reason deliberation exists, not errors to prevent
• "Commitment is operationalized through revision constraints, not persistence axioms": Can specify trigger conditions; explains how new intentions are checked against existing ones
• "Preference over revisions encodes deliberation policy in the revision procedure itself": Priority graphs guide search without enumerating all consistent subsets

The tell-tale question: "How does your agent detect when two desires conflict?"

• Hasn't internalized: "We check if they're logically inconsistent" or "The planner fails when constraints contradict"
• Has internalized: "We use explicit negation (desire(P) and desire(¬P)), then paraconsistent semantics detect the contradiction as a signal invoking preference-ordered revision. Negation-by-failure alone can't detect this—absence of desire(P) isn't contradictory with desire(P). We need affirmative representation of both positive and negative desires."

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