EFTA: a database retrieval algebra for feature-terms

摘要

We define a data-model based on the notation of a feature-term. A Feature-Term Algebra (FTA) for database-retrieval of feature-terms is presented. FTA is comparable to other attempts to extend or modify Relational Algebra to cope with complex objects and set-valued attributes etc., but extends these proposals to an open-world-assumption for the processing of incomplete knowledge. Since we want to define the algebra as an intermediate language for the compilation of feature-logic database-queries, we augment it by a closure-operator to be able to compile recursive queries. Formal semantics of this Extended Feature-Term Algebra (EFTA) are given, its expressive power is investigated, and the algebra is discussed in the context of related work.