Defining Formalisms for Performance Evaluation With SIMTHESys
Electronical Notes in Theoretical Computer Science
Tools for the analysis and modeling of complex systems must be able to support the extensibility of formalisms, reusability of models and customization of formalism compositions. From this perspective, SIMTHESys (Structured Infrastructure for Multiformalism modeling and Testing of Heterogeneous formalisms and Extensions for SYStems) is a new approach to the specification of performability oriented formalisms and the evaluation of models. Its originality emerges from the explicit definition of
... cit definition of both syntax and evolution semantics of the considered formalism elements. The solution of models is made possible by using a set of non-specialized solving engines used to generate automatically formalism-specific reusable solvers. This paper explains how formalisms can be created in SIMTHESys by showing how three widely known modeling languages are successfully implemented. Open access under CC BY-NC-ND license. can be addressed by analyzing models based on many different performability formalisms. Modeling is a complex task because of the heterogeneity of the system needed to be studied. The customization of some of the formalisms for a specific task can simplify the modeling process at a cost of creating a tool to solve a model based on an extended formalism. The idea of creating a tool for each formalism extension seems not to be feasible. Notwithstanding the huge number of known modeling formalisms, they share some basic fundamental ideas that suggests a classification in families. These can be re-grouped using a common solver that can be specialized for the different cases. The SIMTHESys approach, presented in  4 moves onward from such premise to propose a new solution to the problem. SIMTHESys offers a compositional, metamodeling based framework to describe and extend formalisms 5 . This paper aims to demonstrate how to design formalisms belonging to the Exponential Event Formalisms (EEF) family. Three cases are presented, showing how three common performance evaluation frameworks, namely Stochastic Petri Nets (SPN)  , Tandem Finite Capacity Queueing Networks (TFCQN)  and Gordon and Newell Queueing Networks (GNQN)  can be defined using the SIMTHESys approach. Two solution components architectures have been designed for the EEF family. Respectively, they perform stochastic simulation and numerical solution. Additionally, a simple model is analyzed to show the possibilities offered by the solution components. The paper is organized as follows. After a brief review of the SIMTHESys approach to multiformalism modeling in Section 2, in Section 3 the exponential transition based family of formalisms is introduced. Section 4 describes the implementations of SPN, TFCQN and GNQN. Section 5 presents the solution engines for the mentioned family. Conclusions and future work are described in section 6.