Andreas Tolk

Using Web services to integrate heterogeneous simulations in a grid environment

The distributed information technologies collectively known as Web services recently have demonstrated powerful capabilities for scalable interoperation of heterogeneous software across a wide variety of networked platforms. This approach supports a rapid integration cycle and shows promise for ultimately supporting automatic composability of services using discovery via registries. This paper presents a rationale for extending Web services to distributed simulation environments, together with a description and examples of the integration methodology used to develop significant prototype implementations, and argues for combining the power of Grid computing with Web services to further expand this demanding computation and database access environment.

Composable M&S Web Services for Net-Centric Applications

Service-oriented architectures promise easier integration of functionality in the form of web services into operational systems than is the case with interface-driven system-oriented approaches. Although the Extensible Markup Language (XML) enables a new level of interoperability among heterogeneous systems, XML alone does not solve all interoperability problems users contend with when integrating services into operational systems. To manage the basic challenges of service interoperation, we developed the Levels of Conceptual Interoperability Model (LCIM) to enable a layered approach and gradual solution improvements. Furthermore, we developed methods of model-based data engineering (MBDE) for semantically consistent service integration as a first step. These methods have been applied in the U.S. in collaboration with industry resulting in proofs of concepts. The results are directly applicable in a net-centric and net-enabled environment.

What Comes After the Semantic Web - PADS Implications for the Dynamic Web

The Internet started as a web of documents. The Semantic Web is targeting a web of data, enabling efficient machine-to-machine data exchange. In order to utilize the Internet for distributed simulation, procedures are needed for migration, alignment, and orchestration of the execution, which means higher levels of interoperation. This paper introduces related concepts leading to the idea of the Dynamic Web, which will be a web of composable services. This paper is a concept paper written to encourage discussion. It summarizes related ideas and contributions in a loose style and doesn’t claim to be complete or inclusive. Contributions are more than welcome.

Engineering Principles of Combat Modeling and Distributed Simulation: Tolk/Engineering Principles Combat Modeling

Explore the military and combat applications of modeling and simulation Engineering Principles of Combat Modeling and Distributed Simulation is the first book of its kind to address the three perspectives that simulation engineers must master for successful military and defense related modeling: the operational view (what needs to be modeled); the conceptual view (how to do combat modeling); and the technical view (how to conduct distributed simulation). Through methods from the fields of operations research, computer science, and engineering, readers are guided through the history, current training practices, and modern methodology related to combat modeling and distributed simulation systems. Comprised of contributions from leading international researchers and practitioners, this book provides a comprehensive overview of the engineering principles and state-of-the-art methods needed to address the many facets of combat modeling and distributed simulation and features the following four sections:

Reference modelling in support of M&S—foundations and applications

Whether by design or by practice, systems engineering (SE) processes are used more and more often in Modeling and Simulation (M&S). While the two disciplines are very close, there are some differences that must be taken into account in order to successfully reuse practices from one community to another. In this paper, we introduce the M&S System Development Framework (MS-SDF) that unifies SE and M&S processes. The MS-SDF comprises the SE processes of requirements capture, conceptual modelling, and verification and validation (V&V), and extends them to M&S. We use model theory as a deductive apparatus in order to develop the MS-SDF. We discuss the benefits of the MS-SDF especially in the selection between federation development and multi-model approaches and the design of composable models and simulations. Lastly, a real life application example of the framework is provided.

Implied ontological representation within the levels of conceptual interoperability model

The Levels of Conceptual Interoperability Model LCIM has been developed to provide both a metric of the degree of conceptual representation that exists between interoperating systems and also as a guide showing what is necessary to accommodate a targeted degree of conceptual representation between systems. The model was originally developed to support the interoperability of simulation systems, but has been shown to be useful for other domain areas. The model is stratified into seven general levels, and these are introduced and defined. Implied within the model is that the information and processes of one system should be described and that description is then made available to another system. This description of information and processes can take many forms, but is generally an ontological representation. The components of an ontological representation are defined in form and also as elements for the various layers of the LCIM.

Observations on new developments in composability and multi-resolution modeling

MRM (MRM) and Composability are two of the most challenging topics in M&S. They are also related. In this paper, which was written to set the stage for conference discussion of related papers, we discuss how addressing the MRM challenge is sometimes a necessary - although not sufficient - step towards solving the composability challenge. This paper summarizes recent developments in theory drawing distinctions among issues of syntax, semantics, pragmatics, assumptions, and validity. The paper then discusses how technology for ontology development may be useful in improving both composability and MRM. Two examples illustrate how some of the issues arise. One involves a large analytic war gaming system from the past; the other involves current counter-terrorism modeling in which many of the complications are due to the social- science nature of the problem area.

An Architecture for Web-Services Based Interest Management in Real Time Distributed Simulation

The Experimentation Command and Control Interface (XC2I) project has developed an architecture for a Web-service based viewer/controller for use with distributed simulations supporting military experiments. As part of this activity, a capability for Interest Management with three functions is being created. The functions are Role-Based Access Control (RBAC), Area of Interest Management (AOIM), and Aggregation Interest Management (AGIM). While the approach is compatible with High Level Architecture (HLA) for Modeling and Simulation, primary information exchange takes place using the Web services, i.e. software-to-software messaging interfaces that operate over Web protocols such as XML/SOAP. This paper presents a Web Services Internet Management (WSIM) architecture designed to achieve these capabilities in a way that is compatible with simulations using the HLA. The protocols and information flow structure are described, along with the architectures design rationale, interest management rules, and plans for its implementation. The paper concludes with a description of potential for future development of WSIM, including adoption of the Command and Control Information Exchange Data Model (C2IEDM) and use of Overlay Multicast for data distribution.

Ontology for modeling and simulation

This paper establishes what makes an ontology different in Modeling and Simulation (M&S) from other disciplines, vis-a-vis, the necessity to capture a conceptual model of a system in an explicit, unambiguous, and machine readable form. Unlike other disciplines where ontologies are used, such as Information Systems and Medicine, ontologies in M&S do not depart from a set of requirements but from a research question which is contingent on a modeler. Thus, the semiotic triangle is used to present that different implemented ontologies are representations of different conceptual models whose commonality depends on which research question is being asked. Ontologies can be applied to better capture the modelers perspective. The elicitation of ontological, epistemological, and teleological considerations is suggested. These considerations may lead to better differentiation between conceptualizations, which for a computer are of importance for use, reuse and composability of models and interoperability of simulations.

Using Web Services to Integrate Heterogeneous Simulations in a Grid Environment

The distributed information technologies collectively known as Web services recently have demonstrated powerful capabilities for scalable interoperation of heterogeneous software across a wide variety of networked platforms. This approach supports a rapid integration cycle and shows promise for ultimately supporting automatic composability of services using discovery via registries. This paper presents a rationale for extending Web services to distributed simulation environments, including the High Level Architecture (HLA), together with a description and examples of the integration methodology used to develop significant prototype implementations. A logical next step is combining the power of Grid computing with Web services to facilitate rapid integration in a demanding computation and database access environment. This combination, which has been called Grid services, is an emerging research area with challenging problems to be faced in bringing Web services and Grid computing together effectively.