Rule-based languages

The paper presents a survey of the main formal rule-based languages and semantics. Both procedural (fixpoint) and declarative (model-theoretic) semantics are defined and discussed, including inflationary and noninflationary fixpoint semantics, and the semi-positive, stratified and well-founded semantics. The relative expressive power and com-plexity of the various languages are provided. Nondeterministic rule-based languages are also discussed, and it is shown how nondeterminism can circumvent some difficulties concerning the expressive power of the deterministic languages. Finally, languages with value invention (in the spirit of object-creation in oodbs) are presented and issues of expressive power specific to such languages are discussed.