Entity-Relationship Models: Formal Specification and Comparision

Much too often, the Entity-Relationship approach is merely perceived as a set of graphical conventions to grossly sketch the data structures of a future database. It is not uncommon to find in some papers or textbooks a strong confusion between the E-R model, diagrammatic representations of E-R constructs, and E-R-based database design methodologies. However, at present time, the E-R model (or E-R models, to be more precise) can be provided with axiomatic definitions, generally pertaining to logic or set theory. Such a sound theoretical foundation is important in order to give the E-R constructs and query languages precise semantics, to compare different E-R models or to design semantics-preserving schema restructuring, to mention only some applications.