Automatic Mediation between Incompatible Component Interaction Styles

Incompatibility of component interaction styles is identified as a major obstacle to interoperability when using off-the-shelf components or dealing with legacy software in compositional development. It is argued that a language for defining abstract interfaces – AID – can serve as a basis for accommodating heterogeneous interaction styles. AID is independent of any concrete style, such as invocation, pipe-and-filter, event-based or others. An AID text just specifies elementary input and output events which happen at the boundary of a component. Code that mediates between different styles can then be generated automatically from an abstract interface description. The focus of this paper is on mediating between dataflow and invocation interaction. The design of the mediation code for invocation-based interaction with mismatching push/pull modes is described in some detail. How to accommodate event-based interaction is shown in the context of the CORBA Notification Service. Enterprise Java Beans are taken as an example of a complex component model, and the problems of accommodating the message-driven beans of EJB 2.0 are analyzed.