Artificial Intelligence Russell

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Artificial IntelligenceRussell
NorvigChapter 12

• By
• Sukhvinder Bahra

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Practical Planners

• OPTIMUM-AIV
• Generate Plans Monitors
• Replan
• Automatically generate plans
• Input Output Representations
• - Must be expressive easy to understand

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STRIPS inefficiency

• Hierarchical Plans
• Complex Conditions
• Time
• Resources

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Hierarchical Decomposition

• High Level Abstraction
• - not able to directly feed into agents
  effectors.
• Low Level Abstraction
• - too much time and steps.
• Abstract Operator
• Primitive Operator

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Extending the Language

• Partition Operators
• - Primitive Operators
• - Non-Primitive Operators
• Add set of Decomposition Methods.

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Analysis of Hierarchical Decomposition

• Subroutines are good
• - can be combined to create large plans.
• Abstract solution
• Two solutions
• - downward solution
• - upward solution

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• A simplified model
• Assume that there is one solution with n
  primitive steps.
• Time to choose right steps.

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• (see figure12.5)
• Non-Hierarchical Planner
• - worst case O(bn)
• Hierarchical Planner
• - search decompositions to abstract solution

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Decomposition v Approximation

• Hierarchical Planning
• - Hierarchical Decomposition
• abstract, non-primitive operator
• decomposed into steps.
• - Abstraction Hierarchies
• single operator planned at different
• levels of abstraction

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Negated Disjunctive Goals

• Negated Literals
• Unification Function
• p p
• Initial State - dont specify false conditions
• Disjunctive PreConditions - p v q
• Disjunctive Effects - hard to incorporate

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Universal Quantification

• Extend for Universally Quantified PreCondition.
• eg, Clear(b)
• Extend for Universally Quantified Effects.
• eg, Carry(bag,x,y)

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Condition Effects

• Operators have different meanings
• - Blocks world
• Initial state On(a,b)
• Goal state Clear(b)
• Single Operator
• - e.g, Move(b,x,y)
• effect when condition

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Measures of Planning

• Measures can be logical terms.
• Measures that change over time.
• Planners need declarations up-front.
• Resource Measures
• e.g, Cash, GasLevel
• Effect operator
• left-handside is a measure.
• right-handside is expression involving
  measure.

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Temporal Constraints

• Time is a resource.
• Initial-state has a start-time for plan.
• Add time to time for each operation.
• e.g, 10 seconds to pump gallon of gas.
• 3 minutes for rest of filling up.