An integrated simulation environment combining process-driven and event-driven models

A simulation framework that integrates process-driven and event-driven approaches offers a powerful combination of tools to the modeler. In process-driven simulation models, the system can be represented by block diagrams or system networks through which entities flow to mimic real life system objects. In event-driven models, the system can be represented by event graphs, which focus on the abstraction of the event rather than on observable physical entities. In this research, a simulation environment is proposed to integrate both the approaches, i.e. process and event. The main purpose of this research is to mitigate complexity of large models through process orientation, while retaining the control over the attributes, variables and the logic through event orientation. Discrete event simulation is often taught to the students at either the event level or the process level. A simulation tool that effectively preserves both the levels would be useful from the simulation education perspective.;An important feature of standard event graphs is parameterization of the event vertices, allowing similar model sub-graphs to be combined together as a generic sub-graph distinguished by parameter values. A framework based on an Integrated Entity/Event (IE2) approach has been further enhanced to explicitly represent entities at the event-driven level. The integrated simulation framework works towards attenuation of the abstraction involved in parameter passing. The solution lies in explicitly passing the entities through the event-driven model. Event parameters are replaced by entity attributes. The usage of entities in the event-driven layer serves two purpose, (a) reduces the abstraction by manipulating entity objects instead of working with parameters as in a programming language, and (b) gives the intuitive feel of process-driven models to modelers at the event level, which enhances the appeal of the event-driven models.;The advantage of using the entity attributes in the IE 2 model is that the similar model sub-graphs can be combined together as a generic sub-graph distinguished by entity attribute values. At the event level, entities are handled as objects in a way that is analogous to their treatment in the process models. The attributes of an entity are defined by the modeler, enabling the flexibility and explicit handling of entities at the event level. Instead of passing information as event parameters to other nodes as in a programming language, the IE2 model defines them explicitly as attributes of entities that are associated with events as they are scheduled.;The contributions of the IE2 simulation framework can only be realized through a decent interface. The essential elements discussed by Kuljis (1996) were considered in the research as guidelines for constructing user interface for the IE2 simulation framework. Though Buss et al. (2002) attempted to integrate process-driven and event-driven approaches on the user interface level; the interface for IE2model is different by explicitly defining the role of process- and event-driven models in the IE2 simulation framework. In order to measure the benefits of the IE 2 simulation framework as standard simulation software, it has to be tested against current modeling frameworks. An experiment has been conducted to test the features of the IE2 software vis-a-vis pure process-driven models. The test results showed that the average performance of the IE2 simulation framework is better than the pure process-driven models.;The research has successfully integrated two different models i.e. process- and event-driven, in the simulation framework as hierarchical layers. The simulation framework is designed to handle the processing of entities and events. A formal relationship among process-driven models, event-driven models and resident entities, like resources and queues, has been established. This formalism enables the DES (Discrete Event Simulation) models in the integrated simulation framework to be more accurate and elegant by using both process- and event-driven components in a logically consistent way. In an effort to build models that accurately represent real-world structure, this ability is critical.