Lecture-planning-1 - Planning • Chapter 11 • Yet...

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Unformatted text preview: Planning • Chapter 11 • Yet another popular formulation for AI – Logic-based language – One of the most structured formulations • Can be translate into less structured formulations such as state-space, CSP, SAT, etc. What is Planning • Generate sequences of actions to perform tasks and achieve objectives. – States, actions and goals Objective: John wants to go to NYC Plan: taxi(John,home,STL) board(John,plane) fly(plane,STL,JFK) exit(John,plane) taxi(John,JFK,5 th Ave) • Classical planning environment: fully observable, deterministic, finite, and discrete. Difficulty of real world problems • What’s wrong with state-space search, e.g. A*? – Which actions are relevant? Too many irrelevant actions • Board(Mary,plane), board(Tim,plane), taxi(John, home, six flags), fly(plane, LAX, SFO), …. – What is a good heuristic functions? • It is difficult to come up with domain-independent heuristics if only a state-space description is given – How to decompose the problem? • Most real-world problems are nearly decomposable. • E.g. John, Mary, and Tim want to go to different cities Planning language • What is a good language? – Expressive enough to describe a wide variety of problems. – Restrictive enough to allow efficient algorithms to operate on it. – Planning algorithm should be able to take advantage of the logical structure of the problem. • STRIPS Example: air cargo transport Init(At(C1, SFO) ∧ At(C2,JFK) ∧ At(P1,SFO) ∧ At(P2,JFK) ∧ Cargo(C1) ∧ Cargo(C2) ∧ Plane(P1) ∧ Plane(P2) ∧ Airport(JFK) ∧ Airport(SFO)) Goal(At(C1,JFK) ∧ At(C2,SFO)) Action(Load(c,p,a) PRECOND: At(c,a) ∧ At(p,a) ∧ Cargo(c) ∧ Plane(p) ∧ Airport(a) EFFECT: ¬At(c,a) ∧ In(c,p)) Action(Unload(c,p,a) PRECOND: In(c,p) ∧ At(p,a) ∧ Cargo(c) ∧ Plane(p) ∧ Airport(a) EFFECT: At(c,a) ∧ ¬In(c,p)) Action(Fly(p,from,to) PRECOND: At(p,from) ∧ Plane(p) ∧ Airport(from) ∧ Airport(to) EFFECT: ¬ At(p,from) ∧ At(p,to)) [Load(C1,P1,SFO), Fly(P1,SFO,JFK),Unload(C1,P1,JFK), Load(C2,P2,JFK), Fly(P2,JFK,SFO), Unload(C2,P2,SFO)] Example: air cargo transport Init(At(C1, SFO) ∧ At(C2,JFK) ∧ At(P1,SFO) ∧ At(P2,JFK) ∧ Cargo(C1) ∧ Cargo(C2) ∧ Plane(P1) ∧ Plane(P2) ∧ Airport(JFK) ∧ Airport(SFO)) Goal(At(C1,JFK) ∧ At(C2,SFO) ∧ At(P1,SFO) ) Action(Load(c,p,a) PRECOND: At(c,a) ∧ At(p,a) ∧ Cargo(c) ∧ Plane(p) ∧ Airport(a) EFFECT: ¬At(c,a) ∧ In(c,p)) Action(Unload(c,p,a) PRECOND: In(c,p) ∧ At(p,a) ∧ Cargo(c) ∧ Plane(p) ∧ Airport(a) EFFECT: At(c,a) ∧ ¬In(c,p)) Action(Fly(p,from,to) PRECOND: At(p,from) ∧ Plane(p) ∧ Airport(from) ∧ Airport(to) EFFECT: ¬ At(p,from) ∧ At(p,to)) [Load(C1,P1,SFO), Fly(P1,SFO,JFK),Unload(C1,P1,JFK), Load(C2,P2,JFK), Fly(P2,JFK,SFO), Unload(C2,P2,SFO), Fly(P1,JFK,SFO) ] Example: air cargo transport Init(At(C1, SFO) ∧ At(C2,JFK) ∧ At(P1,SFO) ∧ At(P2,JFK) ∧ Cargo(C1) ∧ Cargo(C2) ∧ Plane(P1) ∧ Plane(P2) ∧ Airport(JFK) ∧ Airport(SFO)) Goal(At(C1,JFK)...
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Lecture-planning-1 - Planning • Chapter 11 • Yet...

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