Multi-formalism modeling for the enterprise

No single model can capture the complexities of modern enterprises. Machinery and plants are being instrumented generating large amounts of data. Plants and administrative locations are all interconnected through a variety of networks. These networks have also enabled the creation of very diverse and active social networks within organizations. None of the individual components are new. What is new is their diversity and the speed with which they evolve. When multiple models are used, often expressed in different modeling languages, to capture and support different aspects of the enterprise, it often becomes necessary to have these models interoperate. However, each modeling language, while it offers unique insights, also makes specific assumptions about the domain being modeled. For example, social networks [1] describe the interactions (and linkages) among group members but say little about the underlying organization and/or functional structure of the enterprise. Similarly, organization models [3] focus on the structure of the organization and the prescribed interactions based on authorities and responsibilities but say little about the social/behavioral aspects of the members of the organization. Timed Influence net models [6,7] a variant of Bayesian net models, describe cause-and-effect relationships and can be used to assess the decisions made and alternative courses of action that may be executed by management but say little about the decision makers and operators themselves. In order to address the modeling and simulation issues that arise when multiple models are to interoperate, four layers need to be addressed. The lowest layer, the Physical one, i.e., hardware and software, is a platform that enables the concurrent execution of multiple models expressed in different modeling languages and provides the ability to exchange data and also to schedule the events across the different models. The second layer is the Syntactic layer which ascertains that the right data are exchanged among the models. The Physical and Syntactic layers have been addressed through such developments as the C2 Wind Tunnel (C2WT) [2] by Vanderbilt University in collaboration with UC-Berkeley and George Mason University. The C2WT is an integrated, multi-modeling simulation environment. Its framework uses a discrete event model of computation as the common semantic framework for the precise integration of an extensible range of simulation engines, using the Run-Time Infrastructure (RTI) of the High Level Architecture (HLA) platform. Once the technical means to execute concurrently inter-operating models expressed in different modeling languages is achieved, a third problem needs to be addressed at the Semantic layer, where the interoperation of different models is examined to ensure that conflicting assumptions in different modeling languages are recognized and form constraints to the exchange of data. Finally, at the top layer, the Workflow layer, valid combinations of interoperating models are considered to address specific issues. Different issues require different workflows and may also require domain-specific workflow modeling languages [4]. The use of multiple interoperating models is referred to as multi-modeling (or multiformalism modeling) while the analysis of the validity of model interoperation is referred to as metamodeling.