1 DEVSML: Automating DEVS Execution Over SOA Towards Transparent Simulators Saurabh Mittal*, José Luis Risco-Martín, Bernard P. Zeigler* {saurabh, zeigler} @ece.arizona.edu, jlrisco@dacya.ucm.es *Arizona Center for Integrative M&S ECE Department, University of Arizona Tucson, AZ 85721 Departamento de Arquitectura de Computadores y Automática Universidad Complutense de Madrid 28040 Madrid, Spain Keywords: DEVSML, SOA, Web services, JavaML Abstract Discrete Event Specification (DEVS) formalism has been used to study dynamics of discrete event systems. DEVS environments are typically open architectures that have been extended to execute on various middleware such as CORBA, Grid computing, P2P networks, RMI and others. The present work aims to provide another development environment using the Service Oriented Architecture (SOA) framework. The proposed DEVS Modeling Language (DEVSML) is built on XML and provides model interoperability among DEVS models located at remote locations. The DEVSML environment is built on client-sever paradigm and the simulation is executed at the server’s end. The proposed DEVS atomic and coupled DTDs are open to standardization from the community for successful model sharing and collaboration. The DEVSML framework provides the needed feature of run-time composability of coupled systems using the SOA framework. DEVSML also provides the capability to translate model to and from XML and JAVA programming language leading to model composability and validation. This paper will demonstrate the client application as well as the server architecture underlying the DEVSML framework. 1. Introduction DEVS formalism [1] exists in many implementations, primarily in DEVS/C++ and DEVSJAVA [2]. Extensions of these implementations are available as DEVS/HLA [3], DEVS/CORBA [4], cell-DEVS [5], and DEVS/RMI [6]. Since DEVS is inherently based on object oriented methodology, C++ and Java are the chosen programming languages. Almost all of the extensions capitalize on the underlying object orientation provide by these two programming languages. The models are coded either in C++ or Java. DEVS formalism categorically separates the model, the Simulator and the Experimental frame. However, one of the major problems in this kind of mutually exclusively system is that the formalism implementation is itself limited by the underlying programming language. In other words, the model and the simulator exist in the same programming language. Consequently, legacy models as well as models that are available in one implementation are hard to translate from one language to another even though both the implementations are object oriented. Other constraints like libraries inherent in C++ and Java are another source of bottleneck that prevents such interoperability. The motivation for this work stems from this need of model interoperability between the disparate simulator implementations and provides a means to make the simulator transparent to model execution. We propose DEVS Modeling Language (DEVSML) that is built on eXtensible Markup Language (XML) [7] as the preferred means to provide such transparent simulator implementation. The present work has been done with Java and efforts are ongoing in the direction to provide C++ implementation of the concept. This work is built on the JAVAML research done by Vladimir for DEVS Meta Language [8]. While his work aims to provide a stand-alone XML schema for DEVS formalism that can be used by any of programming implementations, research is still ongoing to specify the logic behavior in atomic models. The present work aims to extend his approach and provide complete behavioral support in DEVSML by implementing the proposed universal Atomic and Coupled DTDs. We look forward toward standardization of these DTDs so that models across the web can participate in Dynamic Modeling & Simulation over Net-centric web services. We have implemented our proposed DTDs in web service architecture; specifically a Service Oriented Architecture (SOA) [9] and paper will illustrate the Server as well as Client designs. We also propose modifications in the DEVS formalism as well that will make a DEVS model to be a DEVS Service model that can be readily deployed using Model-continuity principles [10]. The paper is organized as follows. The next section provides information about the related work. Section 3 provides basic information about the underlying technologies for the development of DEVSML SOA framework. Section 4 provides an overview of DEVSML layered architecture. Section 5 provides detailed DEVS DTDs. Section 6 presents the Web Service Architecture with both Server and Client designs. Section 7 demonstrates how a client can use the DEVSML transparent simulator implementation and compose models with existing remote models. Section 8 provides conclusion and the recommended future work.