Modeling complex structures in object-oriented logic programming

Abstract

In this paper, we present a type model for object-oriented databases. Most object-oriented databases only provide users with flat objects whose structure is a record of other objects. In order to have a powerful expression power, an object-oriented database should not only provide objects but also complex values recursively built using the set, tuple and disjunctive constructors. Our type model presents two notions: that of classes whose instances are objects with identity and that of types whose instances are complex values. The two notions are mixed in that an object is modeled as a pair containing an identifier and a value, and a value is a complex structure which contains objects and values. We define in this context the notions of subtyping and provide a set inclusion semantics for subtyping.