Artificial intelligenceLesson 1 of 2 in the course Planning and constraint satisfaction

HTN Task Types, Decomposition, and Computational Limits

5 flashcards · 5 quiz questions · 5 match pairs · 3 fill-in sentences · English

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Summary

Hierarchical task network (HTN) planning is an approach to automated planning that represents how complex activities can be broken down into simpler tasks. It is useful when a planning problem includes not only a desired outcome but also knowledge about the procedures and dependencies involved in achieving it.

An HTN problem is specified using tasks and relationships among them. Tasks fall into three broad categories.

All flashcards

What is hierarchical task network (HTN) planning?
An automated planning approach that represents activities as hierarchically structured tasks and relationships.
What is a primitive task?
An action that can be executed directly when the current state satisfies its preconditions.
How do compound tasks and goal tasks differ?
A compound task is decomposed into simpler tasks; a goal task specifies a condition to achieve.
What is a task network?
A set of tasks and constraints, such as ordering relationships, that guide how tasks are carried out.
What is a computational limitation of unrestricted HTN planning?
The general planning problem is undecidable, though many restricted forms are decidable.

Quiz questions

  1. What distinguishes a primitive task from a compound task in HTN planning?Answer: A primitive task can execute when its preconditions hold; a compound task must be decomposed.
  2. What does a goal task specify in HTN planning?Answer: A condition that planning must make true.
  3. What does a task network contain?Answer: Tasks together with constraints that govern how they may be carried out.
  4. How does an HTN planner generally turn an initial task network into a solution?Answer: It decomposes compound tasks, respects constraints, and produces executable primitive tasks.
  5. What follows from HTN planning being more expressive than STRIPS in the general case?Answer: HTN can represent hierarchical task structure, but unrestricted planning is undecidable.

Based on the Wikipedia article Hierarchical task network, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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