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Generalized Subsumption

The definition of generality presented so far is local to the set of clauses. Referring to implication instead of the weaker subsumption relationship would also consider generalization w.r.t. current knowledge. In [\protect\citeauthoryearPlotkin1971] a generalization relative to a set of clauses is defined as follows: A clause generalizes a clause relative to a set of clauses if there exists a substitution such that . Buntine defines generalized subsumption of definite Horn clauses as an extension of -subsumption with the restriction that the corresponding clause heads must be about the same concept [\protect\citeauthoryearBuntine1988]. Informally speaking, if a clause generally subsumes clause , then can be converted to by (1) turning variables to constants or other terms, (2) adding atoms to the body, and (3) partially evaluating the body by resolving some clause in with an atom in the body. The third conversion process is additional to the conversion for -subsumption.


Harold Boley, Stefani Possner, Franz Schmalhofer (possner@dfki.uni-kl.de)