A database interface for complex objects

Abstract We describe a formal design for a logical query language using - terms as data structures to interact effectively and efficiently with a relational database The structure of - terms provides an adequate representation for so - called complex objects They generalize conventional terms used in logic programming: they are typed attributed structures, ordered thanks to a subtype ordering Unification of - terms is an effective means for integrating multiple inheritance and partial information into a deduction process We define a compact database representation for - terms, representing part of the subtyping relation in the database as well We describe a retrieval algorithm based on an abstract interpretation of the - term unification process and prove its formal correctness This algorithm is efficient in that it incrementally retrieves only additional facts that are actually needed by a query, and never retrieves the same fact twice