A Hierarchical Database Model for a Logic Programming Language

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This paper presents an extended Clausal Database Model for a logic programming language. Instead of being restricted to one global database, as is the case with Prolog, we allow segmentation of the database into database units that are linked together into a semi-lattice. Each database unit defines a database view which includes clauses that have been asserted into that unit as well as clauses inherited from its 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 the implementation of 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 has a version of assert, retract, and cut.


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database, logic programming, prolog

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University of Pennsylvania

Department of Computer and Information Science

MS-CIS-88-22

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