Relational heterogeneity relaxed by subtyping

Abstract

Homogeneous relation algebra is an elegant calculational framework with many applications in computing science. In one application of relation algebra, called Ampersand, heterogeneous relation algebra is used as a specification language for business processes and information systems. For this purpose a typed version of relation algebra is needed together with subtyping. This requires heterogeneous relational algebra. However, the partiality of the composition and union operators in heterogeneous relational algebra are detrimental to its manipulative power. This paper proposes a practical solution to this problem. The authors suggest to relax the partiality of the heterogeneous operators. By suitable choices this homogenisation allows for a type-based specification language, which has sufficient manipulative power. © 2011 Springer-Verlag.