Ai lecture 7(unit02)
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Goal stack planning is a method in artificial intelligence for managing interactive compound goals by utilizing a stack to hold goals and actions. The process involves working backward from a goal, satisfying preconditions, and potentially creating sub-goals, using methods such as pushing and popping elements from the stack. An example of goal stack planning is provided through a block world puzzle, detailing the initial state, goal state, and the series of actions taken to achieve the goals.
Ai lecture 7(unit02)
- 1. Topic To Be Covered: Goal Stack planning with example Jagdamba Education Society's SND College of Engineering & Research Centre Department of Computer Engineering SUBJECT: Artificial Intelligence & Robotics Lecture No-07(UNIT-02) Prof.Dhakane Vikas N
- 2. Goal stack planning Basic idea to handle interactive compound goal in Artificial Intelligence is Goal stack planning. Here Stack contains Goals, Operators like Add(Push) ,Delete(POP) & Preconditions. We work backwards from the goal, looking for certain action to perform and then trying to satisfy the preconditions of the action. The preconditions of the action become sub goals that must be satisfied. Goal Stack Planning Example:
- 3. Goal stack planning Goal stack planning uses a stack to hold goals and actions to satisfy the goals, and a knowledge base to hold the current state, action schemas. Goal stack is like a node in a search tree; if there is a choice of action, we create branches. Goal stack planning pseudo code : Push the original goal on the stack. Repeat until the stack is empty If stack top is a compound goal, push its unsatisfied sub goals on the stack. If stack top is a single unsatisfied goal, replace it by an action that makes it satisfied and push the action’s precondition on the stack. If stack top is an action, pop it from the stack, execute it and change the knowledge base by the action’s effects. If stack top is a satisfied goal, pop it from the stack. Goal Stack Planning Example:
- 4. Goal stack planning RULE PRECONDITION ACTION Pickup(X) on(X, table) clear(X) handempty holding(X) Putdown(X) Holding(X) on(X, table) clear(X) handempty Stack(X,Y) holding(X) clear(Y) On(X,Y) clear(X) Unstack(X,Y) On(X,Y) clear(X) holding(X) clear(Y) Rules to Solve Block World Puzzle Problem
- 5. Goal stack planning Goal Stack Planning Example: Initial State: On(A,B) :On(C,D) Goal State: On(B,D) & ON (A,B) Solution: Step:1:Start from Goal state with predicate form: ON(B,D)^ON (A,B) ON(B,D)^ON (A,B) ON(B,D) ON (A,B) B A D C D A B In Broken Form
- 6. Goal stack planning Solution: Start from Goal state with predicate form: ON(B,D)^ON (A,B) ON(B,D)^ON (A,B) ON(B,D) ON (A,B) A:Stack(B,D) P:hold(B)^ clear(D) Hold(b) Clear(D) A:Unstack(C,D) P:AE^On(C,D))^ clear(C)- AE On(C,D) clear(C) A:Pickup(B) P:AE^OnT(B)^ clear(B) AE OnT(B) clear(B) A:UnStack(A,B) P:AE^On(A,B))^ clear(A) AE On(A,B) clear(A) A:Putdown(C) P:hold(C)- hold(C) A:Putdown(A) P:hold(A)- hold(A)
- 7. Goal stack planning Solution: Start from Goal state with predicate form: ON(B,D)^ON (A,B) ON(B,D)^ON (A,B) ON(B,D) ON (A,B) A:Stack(A,B) P:hold(A)^ clear(B) Hold(A) Clear(B) A:Pickup(A) P:AE^OnT(A)^ clear(A) AE OnT(A) clear(A)
- 8. Goal stack planning Solution: List OF Actions Action:1 Action:4 Action:2 Action:5 Action:3 Action:6 B A D C B A D C B D C A A B D C A C D B A D C B
- 9. Goal stack planning Solution: List OF Actions Action:7 Goal stack planning utilizes both forward planning as well backward planning. A D B Action:8 C A B D