A modeling approach is here introduced for distributed applications. During the East years computer networks have dominated the world forcing the development of applications operating in a network environment Since new technologies WWW, middleware and co-operative software emerged, distributed applications functionality became rather complex and the requirements from the underlying network increased considerably. Distributed applications usually consist of interacting services provided in a multi-level hierarchy. In order to effectively evaluate their performance through simulation, we introduce a multi-layer object-oriented modeling scheme that facilitates the in-depth and detailed distributed application description and supports most popular architectural models, as the client/server model and ifs variations. Application functionality is described using predefined operations, which can be further decomposed into simpler ones through a multi-layer hierarchy resulting into elementary actions that indicate primitive network operations, such as transfer or processing. Important features of the modeling scheme are extendibility and wide applicability. The simulation environment build according to this modeling scheme is also presented along with an example indicating key features and sample results.
