Web services interaction models. Current practice

Each middleware approach has one or more interaction models associated with it that determine how applications built on top of the middleware interact with each other. Message-oriented middleware (MOM) applications interact rather simply, for example, by posting messages to and retrieving messages from queues. Object-oriented middleware applications such as those based on Corba or Enterprise Java Beans (EJB) interact by invoking methods on distributed objects. Because interaction models significantly influence the types of abstractions a middleware system makes available to applications, they figure prominently in determining the breadth and variety of application integration that the middleware supports. As Web services evolve, they too will acquire standard interaction models; otherwise, their use will be limited to small-scale proprietary systems, rather than providing the standards-based "middleware for middleware" for uniting disparate islands of integration. At this point, however, the industry and standards bodies have yet to reach consensus on Web services interaction models. I consider some of the problems associated with a popular current approach to Web services interaction models