Entity-relationship-attribute designs and sketches (Q2768442)

Entity-Relationship-Attribute (ERA) diagrams are commonly used to specify and design information systems. In a previous paper the authors have shown how ERA diagrams can be enhanced by the inclusion of commutative diagrams and specification of finite limits and finite sums to model constraints and queries. NEWLINENEWLINENEWLINEIn the present paper the authors argue that the categorical notion of sketch is the natural environment to formalize the data base design process. NEWLINENEWLINENEWLINEA data base design is a finite-limit, finite-sum sketch with a terminal node, called EA sketch, a data base state is a model of an EA sketch in a lextensive category. The category of models of an EA sketch is an object of models of the sketch in a 2-category of lextensive categories. Moreover, modelling the same sketch in certain objects in other 2-categories defines both the query language for the data base and the updates for the data base. NEWLINENEWLINENEWLINETherefore, the categorical model idea is used to capture not only the statics of the data base, namely the states, but also the dynamics, namely queries and updates.