Foundations

Deductive databases (DDB) are an extension of Relational databases which support more complex data modeling. In general, they are logic programming systems designed for applications with large quantities of data. Deductive databases generalize relational databases by exploiting the expressive power of (potentially recursive) logical rules and of non-atomic data structures [25].

Such approach greatly simplifies the task of application programmers, providing extended knowledge processing capabilities at the database level. The database becomes not only a data-source, but also a knowledge-source. Thus, a deductive database is a combination of a conventional database containing facts, knowledge base containing rules, and inference engine which allows the derivation of information implied by the facts and rules.

There have been several efforts taken to create such systems [22,6]. In general, a deductive database system is based on the following principles [22]:

1. It has a declarative language, that is logic, serving both as the communication method (query language) and a host language, providing DDL and DML.
2. It supports principle features of database systems, that is efficient access to massive amounts of data, sharing of data, and concurrent access to data.