Cover Model: A Framework for Design and Execution of Distributed Applications

Many problems of distributed object-oriented applications can be uniformly resolved in the frame of approach based on the concept of cover. The cover is defined as an environment which transparently controls all aspects of object’s community life: creation, interaction etc. To enable transparency, an objectoriented application must obey a principle of late binding, a reference to server object being obtained by the client at run time from a system environment. To implement cover services, the technique of metaobject control is applied, which provides extensions of program’s semantics without changing the program code, by means of attaching additional method calls to each application object invocation. A special language (TL) in which the user can incrementally define new metaservices is described and illustrated by numerous examples.