XML-Based Messaging in the JSIM Simulation Environment

1. XML-Based Messaging in the JSIM Simulation Environment Masters Defense by Xueqin Huang

2. Acknowledgements Major professor Dr. John Miller Committee: Dr. Robert Robinson Dr. Dan Everett ...

3. Overview Problem: interoperability in federated simulations Current solution: HLA Proposed solution: Jini and XML Prototype implementation: JSIM Conclusions Future work

4. Problem Reuse of and runtime interoperability b/w simulation components (federates) developed without prior knowledge of each other are the key issues facing federated simulation systems.

5. Current Simulation Interoperability Solution High Level Architecture (HLA) DoD mandate and IEEE standard for simulation interoperability federates interact with each other through a runtime infrastructure (RTI) all exposed simulation functionality and object interactions for each federate must be documented in its Simulation Object Model (SOM) and Federation Object Model (FOM) in accordance with the HLA Object Model Template (OMT) HLA-style simulation systems: Federated Simulations Development Kit; JavaGPSS

6. Problems with HLA RTI offers a low-level operating system like conceptual framework, which makes it a central authorization for running a federation. Pitfalls: too complex to implement, too difficult to scale and evolve goes against the time-honored design principle of layering for distributed systems OMT is a DoD proprietary specification, which cannot be understood by non-HLA style systems

7. Proposed Solution with Jini and XML Jini: the network computing model for the Java platform, offering a service-oriented peer-to-peer communication framework for computers of the future vs. the non-layered approach with HLA RTI a simple programming model that makes it easy to develop Jini-compliant distributed components vs. the complexity in implementing HLA RTI and HLA-compliant components XML: the universal format for data exchange on the Web, offering an open standard for data exchange vs. the proprietary HLA OMT Data Interchange Format (DIF) potential syntactic and semantic interoperability across disparate systems vs. the limited interoperability with HLA

8. Jini: the Network Computing Model for Java Offers service-oriented peer-to-peer communication framework for computers of the future Supports join/discovery protocol lease-based service access security distributed transaction object mobility distributed event model

9. Jini (contd) Participants of the Jini distributed event model remote event object event generator/publisher/source/sender remote event listener/subscriber/target/receiver also allows for third party event routing agents

10. Data Exchange with XML What is XML self-descriptive text-based meta-data standard by W3C Sample XML document (message.xml) Document Type Definition (DTD) (message.dtd) XML Schema (message.xsd) XML RDF (message.rdf) designed for the exchange of data on the Web XML messaging standards The Simple Object Access Protocol (SOAP) ebXML, ... How XML may help with interoperability

11. Data Interoperability with XML Syntactic interoperability well-defined and widely accepted format for data exchange freely and readily available standard-compliant tools Semantic interoperability approach #1: define a domain-specific DTD or XML Schema approach #2: use XML RDF to achieve ontology-based interoperability approach #3: use a general purpose DTD or XML Schema to structure the data while providing additional domain-specific semantic support

12. A Prototype Implementation with JSIM Use Jini-style publish-subscribe eventing with XML-based event data to leverage the power of mainstream interoperability technologies to provide an open and flexible framework for JSIM, a component-based simulation environment targeted for simulation analysts

13. Publish-Subscribe Eventing in JSIM

14. JSIM XML Messages with KOML KOML: the Koala Object Markup Language the KOML serialization package provides bi-directional conversion b/w Java objects and XML uses a single DTD for XML data converted from all types of Java objects allows access and manipulation of the converted XML data at an object level instead of the element level The use of XML as the format for the exchange of simulation data opens up the possibility for JSIM to inter-operate with other simulation systems at both the syntactic and semantic levels.

15. Enhanced Semantic Support via Performatives What are performatives meaning words that act/perform, originated from the �speech acts� theory in modern linguistics; used in the Knowledge Query and Manipulation Language (KQML) to represent agent vocabularies. The use of performatives in JSIM messages further enhances the capability of JSIM components to dynamically make decisions based on the context of their conversations.

16. Architecture of JSIM

17. JSIM Events and Messages

18. Managing XML Data

19. JSIM Data That Needs to be Stored

20. JSIM Database Schema

21. Querying JSIM Database

22. Sample Query Result from JSIM Database

23. Comparison of HLA-Style Systems and Our Proposed JSIM

24. Conclusions Proposed a framework for federated simulations that is open, flexible, extensible, and comparable to an HLA-style system in terms of its support for interoperable federated simulations. Laid a solid foundation for our envisioned system by building a prototype XML-based messaging simulation system in accordance with the framework Designed and implemented an easy-to-evolve database schema for JSIM that supports federated simulations

25. Future Work Guarantee the reliability and order of event delivery in JSIM using Jini event routing agents and event sequence number Explore Jini�s support for distributed transactions to ensure all JSIM federates store their simulation results, or nothing is stored. More semantic support for the XML messages through XML meta-data technologies, such as XML RDF

26. Selected Bibliography Abiteboul, S. Buneman, P, and Suciu, D. (2000). Data on the Web: From Relations to Semi-structured Data and XML. Morgan Kaufmann Publishers. Bollinger, T. (2000). A Guide to Understanding Emerging Interoperability Technologies. Technical paper, Mitre Corporation. July 2000. Burret, R. (2000). XML and Databases. http://www.rpbourret.com/xml/XMLAndDatabases.htm. Finin, T., Fritzen, R., McKay, D., and McEntire, R. (1994). KQML as an Agent Communication Language. Proceedings of the Third International Conference on Information and Knowledge Management (CIKM), ACM Press, November 1994. Hegaret, P.L. (1999). http://www-sop.inria.fr/koala/XML/serialization/. Kuhl, F., Weatherly, R., and Dahmann, J. Creating Computer Simulation System: An Introduction to the High Level Architecture. Published by Prentice Hall PTR. Miller. J. (1999). Guest Editorial. Web-Based Simulation and Modeling, IEEE Potentials. Special Issue on Web-Based Simulation and Modeling, Vol., No. (1999) Sun Microsystems. (2000). Jini Technology Core Platform Specification, v. 1.1. October, 2000. http://www.sun.com/jini/specs/core1_1.pdf