The paper "Composable Mission Spaces and M&S Repositories - Applicability of Open Standards" on top of the recommended reading list of the recent Spring Simulation Interoperability Workshop 2004 (04S-SIW-009) deals with challenge of generating a federation "on the fly." So far, no satisfying solution serving this need has been accomplished. The use of open source doesn't satisfy the industry, which has a vital interest to keep their core solutions in-house and to protect their intellectual property. The use of interface-driven solutions based on black boxes leads to discrepancies and inconsistent federations, as has been shown in the paper on top of the recent Fall Simulation Interoperability Workshop 2003 (03F-SIW-007), in which the Levels of Conceptual Interoperability Model (LCIM) was introduced.
The LCIM shows that meaningful interoperability on the implementation level requires composability on the conceptual level. This circumstance was already pointed out before in slightly different wording, when Zeigler stressed that meaningful interoperability cannot be achieved by standards targeting the implementation level during the Panel Discussion on "Priorities for M&S Standards," conducted together with the Society for Modeling and Simulation (SCS) on the Spring Interoperability Workshop, in Orlando, March 2003.
While the view on the various levels of conceptual interoperability given in 03F-SIW-007 was very data centric, we developed the model further in order to cope more efficient with dynamic issues. The improvements have been influenced by ongoing studies at the University of the Federal Armed Forces in Munich, Germany, dealing with the applicability of linguistic research results to cope with issues like ontology driven interoperable solutions. Marko Hofmann introduced a pragmatic level above the semantic level, meaning that the receiver of the information not only understand its meaning (semantic level), but also knows what to do with it. This led to the definition of the enhanced version of the Levels of Conceptual Interoperability Model (LCIM):
Level 1, technical level: physical connectivity is established allowing bits and bytes to be exchange.
Level 2, syntactical level: data can be exchanged in standardized formats, i.e., the same protocols and formats are supported.
Level 3, semantic level: not only data but also its contexts, i.e. information, can be exchanged; common reference models define the unambiguous meaning of data.
Level 4, pragmatic/dynamical level: information and its use and applicability, i.e. knowledge, can be exchanged; the applicability of information is here defined in an unambiguous form.
Level 5, conceptual level: a common view of the world is established; this level not only comprises the implemented knowledge, but also the interrelations between these elements.
Paper 04S-SIW-009 evaluates several open standards and show how they fit into the LCIM. It shows how they can be applied and how they have to be aligned. Among these standards are XML, SOAP, WSDL, UDDI, the DoD Metadata Registry and Clearinghouse (DDMS), UML (focusing on the improvements of the new version 2.0), the Model Driven Architecture (MDA), and new emerging standards Work Service Flow Language (WSFL), Workflow Environment for Web Services (WEWS), Web Service Offering Language (WSOL), and Business Process Execution Language for Web Services (BPEL4WS). All these solutions contribute to the main issues of distributed simulation, namely contributing to answer the following core questions:
1. How to ensure reuse of the M&S components, which includes the migration from the current solution towards the future standard?
2. How to ensure composability within the standard, i.e., how to make sure that only components are technically composed for which it makes conceptually and operationally sense?
3. How can the composition be orchestrated during the execution, i.e., can different time models be aligned?
The recommended solution of 04S-SIW-009 is to set up a web-based repository. Elements of such a repository dealt with in the paper in more detail are the Common Namespace Management and the Developing of a Common Shared Model of the Joint and Combined Mission Space.
Common namespace management must not be limited to tag set administration, but it must use the means of common data engineering to work towards a common ontology. However, the DDMS mentioned in the standard sector, the DoD Metadata Registry and Clearinghouse processes, must be part of this solution to avoid a solution different from the solution supporting Joint Command and Control (JC2) within the Global Information Grid (GIG).
For the Developing of a Common Shared Model of the Joint and Combined Mission Space, existing standards can be enahnced and modified. That UML can be used to describe dynamics of agile models should be obvious, in particular when M&S formalisms like DEVS are used to enrich the actual set of diagrams. These methods can be used to reach level 4 of interoperability in the LCIM, and they maybe even applicable to set up a real common conceptual model in the future, in other words: Level 5 is in reachable distance.
In summary, the best paper of SIW S04 shows how the consequent application of web-based open standards in an aligned and harmonized manner can be used to make the vision of a web-based repository of composable M&S applications a reality now, not only in a distant future. We already have in hand what we need to start these processes.
For the upcoming Fall Simulation Interoperability Workshop, the next step of this processes will be described, namely the use of "Metamodels and Mappings" extending the LCIM by a metamodel dimension and utilizing platform independent models to enable the mapping of alternative solutions to each other, hence ending the everlasting war on which standard solution is more compatible than the others (04F-SIW-105).
For more information on these topics, please refer to:
[Tolk & Muguira, 2003] Andreas Tolk and James A. Muguira. The Levels of Conceptual Interoperability Model (LCIM). Fall Simulation Interoperability Workshop 2003, Paper 03F-SIW-007, Orlando, Florida, September 2003
[Tolk, 2004a] Andreas Tolk. Composable Mission Spaces and M&S Repositories – Applicability of Open Standards. Spring Simulation Interoperability Workshop 2004, Paper 04S-SIW-009, Arlington, VA, April 2004
[Tolk, 2004b] Andreas Tolk. Metamodels and Mappings – Ending the Interoperability War. (submitted) Fall Simulation Interoperability Workshop 2004, Paper 04F-SIW-105, Orlando, Florida, September 2004
To view online visit:
03F-SIW-007 - Application of Data Fusion to Military Simulation
www.sisostds.org/doclib/doclib.cfm?SISO_RID_1005115
04S-SIW-009 - Composable Mission Spaces and M&S Repositories - Applicability of Open Standards
www.sisostds.org/doclib/doclib.cfm?SISO_RID_1005430
04F-SIW-105 - Metamodels and Mappings – Ending the Interoperability War
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