Performance Modeling of Distributed Collaboration Services

This paper deals with performance modeling of distributed applications, service compositions and workflow systems. From the functional perspective, the distributed application is modeled as a collaboration involving several roles, and its behavior is defined in terms of a composition from several sub-collaborations using the standard sequencing operators found in UML Activity Diagrams and similar formalisms. For the performance perspective, each collaboration is characterized by a certain number of independent input events and dependent output events, and the performance of the collaboration is defined by the minimum delays that apply for a given output event in respect to each input event on which it depends. We use a partial order to model these delays. The paper explains how these minimum delays can be measured through testing. It also provides general formulas by which the performance of a composed collaboration can be calculated from the performance of its constituent sub-collaborations and the control structure which determines the order of execution of these sub-collaborations. Proofs of correctness for these formulas a given and a simple example is discussed throughout the paper.