What is a Planning Graph?
A Planning Graph is a data structure primarily used in automated planning and artificial intelligence to find solutions to planning problems. It represents a planning problem’s progression through a series of levels that describe states of the world and the actions that can be taken. Here’s a breakdown of its main components and how it functions:
- Levels: A Planning graph has two alternating types of levels: action levels and state levels. The first level is always a state level, representing the initial state of the planning problem.
- State Levels: These levels consist of nodes representing logical propositions or facts about the world. Each successive state level contains all the propositions of the previous level plus any that can be derived by the actions of the intervening action levels.
- Action Levels: These levels contain nodes representing actions. An action node connects to a state level if the state contains all the preconditions necessary for that action. Actions in turn can create new state conditions, influencing the subsequent state level.
- Edges: The graph has two types of edges: one connecting state nodes to action nodes (indicating that the state meets the preconditions for the action), and another connecting action nodes to state nodes (indicating the effects of the action).
- Mutual Exclusion (Mutex) Relationships: At each level, certain pairs of actions or states might be mutually exclusive, meaning they cannot coexist or occur together due to conflicting conditions or effects. These mutex relationships are critical for reducing the complexity of the planning problem by limiting the combinations of actions and states that need to be considered.
Planning Graphs in AI
Planning graphs play a vital role in AI planning by visually representing possible states and actions that aid in decision-making. This article explores STRIP-like domains that construct and analyze the compact structure called graph planning. We will also delve into the role of mutual exclusion, providing a suitable example using a graph planning algorithm.
Table of Content
- What is a Planning Graph?
- Levels in Planning Graphs
- Working of Planning Graph
- Mutual Exclusion in Planning Graph
- Planning a Graph for a CAKE Problem
- Steps in the Graph Plan Algorithm
- Properties of Graph Plan
- Conclusion
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