Semantics and verification of object-role models

Abstract

In this paper we formalize data models that are based on the concept of predicator, the combination of an object type and a role. A very simple model, the Predicator Model, is introduced in a rigid formal way. We introduce the concept of population as an instantiation of an information structure. A primitive manipulation language is defined in the style of relational algebra. Well-known types of constraints are defined in terms of the algebra introduced, as restrictions on populations. They are given more expressive power than is usually the case. Constraints are of central importance for identification purposes. Weak identification ensures identifiability of objects within a specific population, while structural identification ensures identifiability of objects within every population. Different levels of constraint inconsistency are defined and it is shown that the verification of two important levels is NP-complete.