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Web Services Supporting Simulation to Global Information Grid. Mark Pullen George Mason University with support from partners Don Brutzman, NPS Andreas Tolk, ODU Katherine Morse, SAIC. Extensible Modeling & Simulation Report http://www.movesinstitute.org/xmsf.
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Web Services SupportingSimulation to Global Information Grid Mark Pullen George Mason University with support from partners Don Brutzman, NPS Andreas Tolk, ODU Katherine Morse, SAIC
Extensible Modeling & Simulation Reporthttp://www.movesinstitute.org/xmsf • Web-based technologies applied within an extensible framework will enable a new generation of modeling & simulation (M&S) applications to emerge, develop and interoperate. • Support for operational tactical systems is a missing but essential requirement for such M&S applications frameworks. • The framework of Extensible Markup Language (XML)-based languages can provide a bridge between forthcoming M&S requirements and open/commercial web standards, while continuing to support existing M&S technologies. • Compatible and complementary technical approaches are now possible for model definition, simulation execution, network-based education, network scalability, and 2D/3D graphics views. • The Web approach for technology, software tools, content production and broad use provides best business cases from an enterprise-wide (i.e. world wide) perspective.
Web Services • Definition: a self-contained, self-describing unit of modularity for publishing and delivering XML-based digital services over the Internet. • natural extension of the concept of a resource • sits on the network and does something we need • accepts messages and returns replies • encoded in XML • peer-to-peer or client-server
Specifying Web Services • Externally visible behavior is described in terms of the syntax, semantics, and sequencing of messages exchanged between the service provider and its client • Described using an XML Schema vocabulary • Web Service interface description document specifies a contract between the service provider and its client.
Web Services Model Service Provider Service Consumer Service Registry
XML • Universal meta-language of the Web • Used for data, content, messaging, and computing to provide point-to-point integration in a platform-neutral way • Document structure, content and semantics defined by XML schema • Basis for a new generation of lightweight application-level protocols now emerging
Simple Object Access Protocol(SOAP) • XML-based, lightweight messaging protocol for exchange of typed information in decentralized, distributed environments • Enables interoperability among (existing) distributed applications running on disparate, heterogeneous platforms using a modest infrastructure • Guiding principles are simplicity and extensibility by modularity. • Does not define a programming model or require a specific network transport. • Simply consists of a modular packaging mechanism and a set of encoding rules.
Implementing Web Services • Develop an ontology for data management • use it to define an XML tagset • Define the services to be provided • any function is a candidate • an example: digital terrain • Provide software for each service • new development: generally in Java • legacy code easily wrapped to appear as a service • Package the XML in SOAP for transmission • Interoperate! • examples: XDV via Web-Enabled RTI; XBML
Critical Points • XML is a mature technical standard for information exchange • and getting even better: compressed/binary form soon • but it is useless without data management namespace • SOAP is an effective means to transport XML-encoded data across networks • but it is only a component of a larger system • There is no magic here, just better technology • software is still complex and expensive! • but interoperation is simpler to achieve • and technology development paid for commercially
How Does This Relate to the GIG? • XML/SOAP are great for data distribution • support the Common Operating Picture • But to get to the next level up, we still need to deal with meta-information • behavioral representation composability, as in XBML • The simulation community has begun work on Web Service Profiles to support this • The same technologies empower the GIG • we need to manage the namespaces and meta-information so they work together • then M&S becomes a powerful C4I system capability
M&S Service One View of the Future Communities of Interest Etc. GIG Enterprise Services M&S Service Comms Backbone ESM Messaging Mediation Security User Asst Net Centric Enterprise Services Discovery Collaboration Storage App M&S Service Notional only - does not imply one “box” per service etc. Edge Users
References • Two key papers are available today as handouts • A collection of publications is at: http://netlab.gmu.edu/xmsf/pubs