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Datalog


Datalog is a declarative logic programming language that syntactically is a subset of Prolog. It is often used as a query language for deductive databases. In recent years, Datalog has found new application in data integration, information extraction, networking, program analysis, security, and cloud computing.

Its origins date back to the beginning of logic programming, but it became prominent as a separate area around 1977 when Hervé Gallaire and Jack Minker organized a workshop on logic and databases.David Maier is credited with coining the term Datalog.

Unlike in Prolog, statements of a Datalog program can be stated in any order. Furthermore, Datalog queries on finite sets are guaranteed to terminate, so Datalog does not have Prolog's cut operator. This makes Datalog a truly declarative language.

In contrast to Prolog, Datalog

Query evaluation with Datalog is based on first order logic, and is thus sound and complete. However, Datalog is not Turing complete, and is thus used as a domain-specific language that can take advantage of efficient algorithms developed for query resolution. Indeed, various methods have been proposed to efficiently perform queries, e.g., the Magic Sets algorithm, tabled logic programming or SLG resolution.


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