An ER Calculus for the Entity-Relationship Complex Model
Christine E. Parent, Hélène Rolin, Kokou Yétongnon, Stefano Spaccapietra · 1989
The entity-relationship (ER) approach still lacks sound and complete theoretical foundations for modern, more sophisticated, ER models. We already proposed an algebra as a basis for data manipulation languages for such an advanced ER model, called ERC. The aim of this paper is to formally define a companion ERC calculus. We first investigate a general calculus, which is more natural (straight derivation from the model), but too powerful as it also allows expressions which are semantically inconsistent with the existing database. We then define what restrictions should be imposed, and how, to lead to a calculus whose expressive power is equivalent to the one of the ERC algebra. Keywords: entity-relationship, database theory, data manipulation languages, query languages, algebra, calculus _________________________________________ This work was supported by a research contract with INRIA as part of the "Programme de Recherches Coordonnes Bases de donnes de troisime gnration" (PRC BD3)....