Extending logic programming

摘要

An extension of logic programming, called "ordered logic programming", which includes some abstractions of the object-oriented paradigm, is presented. An ordered program consists of a number of modules (objects), where each module is composed by a number of rules possibly with negated head predicates. A sort of "isa" hierarchy can be defined among the modules in order to allow for rule inheritance. Therefore, every module sees its own rules as local rules and the rules of the other modules to which it is connected by the "isa" hierarchy as global rules. In this way, as local rules may hide global rules, it is possible to deal with default properties and exceptions. This new approach represents a novel attempt to combine the logic paradigm with the object-oriented one in knowledge base systems. Moreover, this approach provides a new ground for explaining some recent proposals of semantics for classical logic programs with negation in the rule bodies and gives an interesting semantics tologic programs with negated rule heads.