IJCAI Introduction

1
Temporal Planning Part 2
Brian C. Williams 16.412J/6.834J Oct 3rdst, 2001
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2
Goals
Histories(?)
Projective Task Expansion
Scheduler
Temporal Planner
Flexible Sequence (Plans)
Task Dispatch
Plan Runner
Goals
Modes
Reactive Task Expansion
Commands
Observations
3
Outline

• Representing Plans
• Representing Time
• Plan Consistency and Scheduling

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Cassini Saturn Orbital Insertion
courtesy JPL
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Planning in a continuous world
Attitude Control System
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Planning in a continuous world

• Turn (a, b)

Attitude Control System
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Planning in a continuous world

• Turn (a, b)

Attitude Control System
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Planning in a continuous world

• Turn (a, b)

Attitude Control System
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Planning in a continuous world

• Turn (a, b)

Attitude Control System
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Planning in a continuous world

• Turn (a, b)

Attitude Control System
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Planning in a continuous world

• Turn (a, b)

Attitude Control System
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Planning in a continuous world

• Point (b)

Attitude Control System
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Planning in a continuous world

• Point (b)

Attitude Control System
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Action/State dichotomy in a continuous world

• Turn is an action, Point is a state
• Both Turn and Point are actions
• Both Turn and Point are state

Point (b)
Turn (a, b)
Attitude Control System
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Both Actions and States are Tokens
Thrust Goals
Power
Attitude
Thrust (b, 200)
Engine
Off
Warm Up
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Planning Constraints are Specified by
Compatibilities
Thrust Goals
Power
equals
contained_by
Point(?x)
Attitude
contained_by
meets
met_by
Thrust (?x, ?y)
Engine
Warm Up
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Example of Compatibility Instantiation
Thrust Goals
Power
contains
Attitude
Thrust (b, 200)
Engine
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Example of Compatibility Instantiation
Thrust Goals
Power
equals
contained_by
Point(b)
Attitude
contained_by
meets
met_by
Thrust (b, 200)
Engine
Warm Up
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Planner/Scheduler Architecture
Engine
Domain Knowledge
Goals
Plan
Plan Database
Initial state
to EXEC
from EXEC
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Planner Resolves Flaws
PLAN
NO
Uninstantiated compatibility
. . .
Instantiate compatibility
. . .
Backtrack
Schedule token
NO
YES
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Types of Flaws

• No Disjunct of Compatibility Selected.
• Unsatisfied Subgoal
• There is a hole in the timeline immediately
  before Thrust (b, 200)
• Floating Token, Needs to be Placed on Timeline.
• Uninstantiated Variable in a Token
• Thrust (?x a, b, c, ?y 190, 300

The Plan Database can be modified only by
primitives that resolve each of these flaws.
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Planner/Scheduler Architecture
Engine
Domain Knowledge
Search Control
Goals
Plan
Plan Database
Initial state
to EXEC
from EXEC
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Search Control Determines Order and Type of Flaw
Resolution
PLAN
T
f2I(P) Plan has no subgoal flaws
Unsatisfied subgoal
Search Control
. . .
Instantiate subgoal
. . .
. . .
Backtrack
Schedule token
f1I(P) Plan is consistent
F
T, ?
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Search Control Language
met_by
Turning_on( )
Camera
(subgoal (master-match (Camera Ready))
(slave-match (Camera Turning_on)) ?
(priority 50) (method-priority ((method
add) (sort asap))
((method connect))
((method defer))))
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DS1 Planner/Scheduler

• DS1 PS is a constraint-based, backtrack search,
  generative planner operating on a fully temporal
  domain model
• Model size (Remote Agent Experiment)
• state variables 18
• procedure types 42
• Plan size
• tokens 154
• variables 288 (81 time points)
• constraints 232 (114 distance bounds)
• Performance
• search nodes 649
• search efficiency 64

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Goals
Histories(?)
Projective Task Expansion
Scheduler
Temporal Planner
Flexible Sequence (Plans)
Task Dispatch
Plan Runner
Goals
Modes
Reactive Task Expansion
Commands
Observations