Section 6 : Reasoning with default information

Commentary

Section Goals

• To discuss the basic ideas of reasoning with default information.

Learning Objectives

Learning Objective 1

• Discuss the open and closed world assumption.
• Outline the basic problems and solutions of nonmonotonic and default logic.
• Explain the following concepts or terms:
  • Open and closed-world assumption
  • Negation as failure
  • Stable model
  • Answer set
  • Answer set programming
  • Nonmonotonic logic
  • Circumscription
  • Default logic
  • Truth maintenance system
  • Belief revision

Objective Readings

Required readings:

Reading topics:

Reasoning with Default Information, Truth Maintenance Systems (see Sections 12.6 - 12.7 of AIMA3ed).

Supplemental Readings

Eiter, T., Ianni, G., Lukasiewicz, T., Schindlauer, R., and Tompits, H. (2008). Combining answer set programming with description logics for the Semantic Web. Artificial Intelligence, 172(12-13), 1495-1539.

Lifschitz, V. (2002). Answer set programming and plangeneration. Artificial Intelligence, 138(1-2), 39-54

Objective Questions

• Name some of the newly-developed truth maintenance systems.
• When are closed-world assumptions actually adopted?
• What methods are introduced to handle "negation" problems?

Objective Activities

• Explore answer set programming methods for description logic (as introduced in the Supplemental Readings of this section).