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A Hierarchical Database Model for a Logic Programming Language
March 1, 1988
This paper presents an extended Clausal Database Model for a logic programming language. Instead of being restricted to a single global database, as in Prolog, we allow the database to be segmented into units linked together into a semi-lattice. Each database unit defines a database view that includes clauses asserted in that unit, as well as clauses inherited from ancestors higher in the lattice structure. This model supports arbitrary retraction. Retracting a clause in a database unit effectively blocks its inheritance for that unit and all of its descendants. Motivations for using this model are given. We also discuss implementing a Prolog meta-interpreter that uses this model. (hereafter referred to as (Phd or Prolog Hierarchical Database). This meta-interpreter is in the spirit of Prolog and therefore includes versions of assert, retract, and cut.
TechReport
University of Pennsylvania
Department of Computer and Information Science
MS-CIS-88-22
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