1 / 10

CS598-EA Logic in AI / Logic-Based AI Lecture #3

CS598-EA Logic in AI / Logic-Based AI Lecture #3. Professor: Eyal Amir Spring Semester 2009. Previously. Logic: propositional, first-order, equality. Today: Examples in FOL: Situation Calculus (Temporal Reasoning). Sitatuation Calculus Language & inference in First-Order Logic

ranger
Download Presentation

CS598-EA Logic in AI / Logic-Based AI Lecture #3

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CS598-EALogic in AI / Logic-Based AILecture #3 Professor: Eyal Amir Spring Semester 2009

  2. Previously • Logic: propositional, first-order, equality

  3. Today: Examples in FOL: Situation Calculus (Temporal Reasoning) • Sitatuation Calculus • Language & inference in First-Order Logic • Frame problem and Explanation Closure • Other problems: Ramification; Qualification • Action Languages • Event Calculus • Applications and tasks

  4. Situation Calculus • A first-order language for describing the effects of actions and events over time • Constants: S0 – initial state; action constants • Functions: result(act,situation) [= do(act,sit.)] • Predicates: “fluents” – properties that change over time at(1, S0) at(x,s) at(x+1,result(move_fwd,s)) Query: at(1+1,s’)  ans(s’) ? at(1+1,s’)  ans(s’)

  5. Situation Calculus • Requires axioms describing effects and non-effects of actions/events • Can be used for planning, projection, diagnosis, filtering (tracking) • Frame Problem: the compact and natural-language-like specification of effects of actions • Qualification Problem: the preconditions of actions

  6. Situation Calculus: Details • Types • Situations: S0, variables, result(act,situation) • Actions: action constants, functions • E.g., go(agent,loc1,loc2) • Fluents: features (propositions, predicates, functions) that change over time • E.g., at(agent1,loc1,situation) • Atemporal features: predicates, functions, object constant symbols

  7. Situation Calculus: Details • Basic axiom types • Initial state description: at(agent1,loc1,S0) • Possibility of action: Preconds(s)  Poss(a,s) • Effects of action: Poss(a,s)  fluents(do(a,s)) • Observations

  8. Situation Calculus: Frame Problem • How do we specify that things don’t change? • Frame Axioms • Nonmonotonic techniques • Explanation closure • Successor-State axioms

  9. Situation Calculus: Ramification • How do we specify ramifications of our actions? • Compilation into effect axioms • State constraints

  10. Situation Calculus: Details • Basic axiom types • Initial state description: on(A,B,S0) • Possibility of action: • PrecondsA(s)  Poss(A,s) • PrecondsA formula containing exactly one situation argument • Effects of action: • Poss(a,s)  (F(s)  F’(do(a,s))) • F,F’ formulae that contain exactly one situation argument • Observations • On(A,B,do(pickUp(A,B,S0)))

More Related