DisLog - A Disjunctive Deductive Database Prototype
(system description)


by Dietmar Seipel 
Universität Würzburg, Germany 


Abstract 

DISLOG is a system for reasoning in disjunctive deductive databases. It seeks to combine features 
of disjunctive logic programming, such as the support for incomplete information, with those of 
deductive databases, such as all-result inference capabilities. Several basic operators are provided 
for logical and non-monotonic reasoning: The logical consequence operator derives all logically 
implied disjunctive clauses from a disjunctive database. The non-monotonic operators are seman-
tically founded on generalizations of the well-known closed-world-assumption and the negation-
as-failure concept.
Reasoning in disjunctive deductive databases is very complex, even for small examples. Many dif-
ferent optimization techniques are integrated in DISLOG to speed up the application performance. 
The clause tree is used as a data structure that allows for an efficient and transparent evaluation.
The DISLOG-system has been developed in PROLOG - currently a core part of DISLOG is reim-
plemented in C++. DISLOG offers two different types of user interfaces. The user-friendly inter-
faces allow for quickly experimenting with semantics on example databases - which can even be 
done remotely through the WWW. The DISLOG-library provides various operators that can be 
loaded into PROLOG applications.