DMSO Technical Exchange 3 Oct 03 1

Web Services SupportingSimulation to Global Information Grid

Mark Pullen

George Mason Universitywith support from partners

Don Brutzman, NPS

Andreas Tolk, ODU

Katherine Morse, SAIC

DMSO Technical Exchange 3 Oct 03 2

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.

DMSO Technical Exchange 3 Oct 03 3

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

DMSO Technical Exchange 3 Oct 03 4

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.

DMSO Technical Exchange 3 Oct 03 5

Web Services Model

ServiceProvider

ServiceConsumer

ServiceRegistry

DMSO Technical Exchange 3 Oct 03 6

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

DMSO Technical Exchange 3 Oct 03 7

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.

DMSO Technical Exchange 3 Oct 03 8

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

DMSO Technical Exchange 3 Oct 03 9

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

DMSO Technical Exchange 3 Oct 03 10

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

DMSO Technical Exchange 3 Oct 03 11

One View of the Future

Comms

Backbone

Edge Users

GIGEnterpriseServices

NetCentric

Enterprise Services

MessagingESM

Discovery Collaboration

Mediation Security

AppStorage

Notional only - does not imply one “box” per service etc.

Etc.

UserAsst

M&S Service

M&S Service

M&S Service

Communities of Interest

DMSO Technical Exchange 3 Oct 03 12

References

• Two key papers are available today as handouts

• A collection of publications is at:

http://netlab.gmu.edu/xmsf/pubs