Distributed programming with typed events
The remote-procedure-call abstraction, including its derivates (underlying, for example, Java RMI, CORBA, and .NET), currently represents one of the most popular paradigms for devising distributed applications. Objects (when acting as servers) are invoked remotely (by clients) through proxies (also called stubs). Because proxies offer the same interfaces as their respective associated remote objects, they hide distribution details, leading to a convenient distributed-programming style that enforces type safety and encapsulation. However, RPC-style interaction does not apply equally well in all contexts. In its classic form, it tends to strongly synchronize-and hence couple-the invoking and invoked objects. Several proposed asynchronous variants of RPC illustrate the severity of this drawback. Type-based publish-subscribe is an appealing candidate programming abstraction for inherently decoupled and completely decentralized applications that run over large-scale and mobile networks. Like RPC, TPS enforces type safety and encapsulation; unlike RPC, it provides decoupling and scalability. To illustrate, we discuss two TPS implementations in Java.