Algebra Transformation Systems and their Composition

Algebra transformation systems are introduced as formal models of components of open distributed systems. They are given by a transition graph modelling the control ow and partial algebras and method expressions modelling the data states and their transformations. According to this two{level structure they cover both labelled transition systems and rule based speciication approaches, corresponding to information, computation and engineering viewpoint models. Diierent composition operations for algebra transformation systems are investigated. Limits and colimits model parallel and sequential composition of components, signature morphisms yield appropriate syntactical support for such compositions. The most important compositionality properties known from algebraic speciication, like colimits of signatures and amalgamation of models, also hold for the framework of algebra transformation systems.