A prime rule is called redundant if it is not present in any irredundant prime knowledge base which is logically equivalent to the given one. Redundant rules can be viewed as the ``least important'' prime rules of a knowledge base. The recognition of redundancy of a particular prime rule in a knowledge base will eliminate such rule from consideration in any future simplifications of the knowledge base.
This paper provides combinatorial characterization of essential and redundant
rules of propositional Horn knowledge bases, and develops, whenever possible,
efficient computational procedures for recognizing essentiality and redundancy
of prime rules of Horn knowledge bases.
Paper available at: ftp://dimacs.rutgers.edu/pub/dimacs/TechnicalReports/TechReports/1994/94-42.ps