A Framework for Simulation Models of Service-Oriented Architectures

Abstract Service-Oriented Architectures (SOA) are one of the main paradigms for future software systems. Since these software systems are composed of a large number of different components it is non trivial to assure an adequate Quality of Service (QoS) of the overall system and performance analysis becomes an important issue. To consider performance issues early in the development process, a model based approach becomes necessary which has to be embedded into the development process of SOA to avoid overhead and assure consistency. In particular the specification of the software system should be used as a base for the resulting performance model. However, since common specification techniques for SOA are very high level, many details have to be added to come to an executable simulation model which is often needed for a detailed analysis of performance or dependability. This paper presents an approach which combines an extended version of process chains to describe the SOA components and some quantitative specifications at the higher levels. For the modelling of the detailed architecture and protocols the simulation tool OMNeT++ is used. Both modelling levels are combined resulting in an executable simulation model for the whole architecture

"QN + PN = QPN" - Combining Queueing Networks and Petri Nets

System analysis is often done due to qualitative and quantitative aspects. Queueing networks and Petri nets are suitable and wide spread model worlds for such a form of analysis, because for both a well founded theory exists. The problem is that Petri nets and queueing networks are only suitable for qualitative analysis resp. quantitative analysis. So the analyst has to create two models of the same system. In recent years several model worlds have been developed, combining qualitative and quantitative aspects thus reducing the modelling effort. The stress nowadays is on timed and stochastic Petri net models. The main disadvantage of these model worlds lies in the difficulties of describing scheduling strategies with Petri net elements. This paper describes a new model world, the QPN world, combining queueing networks and Petri nets for qualitative and quantitative analysis eliminating this disadvantage. It is shown that queueing networks, Petri nets and timed and stochastic Petri nets..

Queueing Petri Nets - A Formalism for the Combined Qualitative and Quantitative Analysis of Systems

System analysis is often needed with respect to both qualitative and quantitative aspects. In the last decades, several formalisms have been developed that attempt to combine these aspects in one description. Present emphasis is on Stochastic Petri Nets. Amongst others, one disadvantage of these formalisms lies with the difficulties when describing scheduling strategies with Petri Net elements. This article describes a new version of Queueing Petri Nets (QPNs), which combines Queueing Networks and Petri Nets, aiming at eliminating these disadvantages. The new version also exhibits the modeling of timed transitions and 'timeless' queues for describing pure scheduling mechanisms. QPNs are a superset of Queueing Networks and (Generalized Stochastic) Petri Nets. The analysis of QPNs is discussed and it is shown that efficient analysis techniques from Petri Net theory can be exploited for analysis of QPNs, thus supporting the general objective of combining Petri Net and Queueing Network for..