DURAL: an Extended Prolog Language

This paper proposes a new programming language DURAL which is an extension of the Prolog language. DURAL takes advantage of modal logic to classify clauses. The main features of DURAL are the following: 1) Modal symbols are introduced to discriminate between clauses. 2) The relative Horn clause represents the clause containing executable predicates. 3) The unit resolution as well as input resolution is adopted to facilitate debugging.