Transcript Document

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
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Extensible Modeling & Simulation Report
http://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.
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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
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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.
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Web Services Model
Service
Provider
Service
Consumer
Service
Registry
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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
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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.
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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
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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 XMLencoded 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
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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 metainformation so they work together
– then M&S becomes a powerful C4I system capability
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One View of the Future
M&S
Service
Communities of Interest
Etc.
GIG
Enterprise
Services
M&S
Service
Comms
Backbone
ESM
Messaging
Discovery
Edge Users
Mediation
Collaboration
Storage
Security
User
Asst
App
M&S
Service
Net
Centric
Enterprise
Services
Notional only - does not imply one “box” per service etc.
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References
• Two key papers are available today as
handouts
• A collection of publications is at:
http://netlab.gmu.edu/xmsf/pubs
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