Reasoning in Inconsistent Knowledge Bases

John Grant, V. S. Subrahmanian

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


Databases and knowledge bases could be inconsistent in many ways. For example, during the construction of an expert system, we may consult many different experts. Each expert may provide us with a group of rules and facts which are self-consistent. However, when we coalesce the facts and rules provided by these different experts, inconsistency may arise. Alternatively, knowledge bases may be inconsistent due to the presence of some erroneous information. Thus, a framework for reasoning about knowledge bases that contain inconsistent information is necessary. Such a framework was described in [1], [21]. However, existing frameworks for reasoning with inconsistency do not support reasoning by cases and reasoning with the law of excluded middle (“everything is either true or false”). In this paper, we show how reasoning with cases, and reasoning with the law of excluded middle may be captured. We develop a declarative and operational semantics for knowledge bases that are possibly inconsistent. We compare and contrast our work with work on explicit and non-monotonic modes of negation in logic programs and suggest under what circumstances one framework may be preferred over another.

Original languageEnglish (US)
Pages (from-to)177-189
Number of pages13
JournalIEEE Transactions on Knowledge and Data Engineering
Issue number1
StatePublished - Feb 1995
Externally publishedYes


  • deductive databases
  • Logic programming
  • nonmonotonic negation
  • reasoning with inconsistency

ASJC Scopus subject areas

  • Information Systems
  • Computer Science Applications
  • Computational Theory and Mathematics


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