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SOA, XML soothe integration worries

Experts at this week's XML Conference 2004 relay how XML and service-oriented architecture solves critical integration challenges.

WASHINGTON, D.C. -- Michael Hu is no Scotland Yard inspector. But his problem-solving skills may just be on par with any of the United Kingdom's finest detectives.


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The challenge facing Hu, lead architect for the Police Information Technology Organization in the UK, was to integrate a large number of 30-year-old legacy systems with the organization's newer heterogeneous systems, taking into account a complex range of users and user scenarios, and all the while figuring out a standardized method of giving the UK's 52 police forces critical data and applications in real time.

The integration scenario facing Hu screamed out for the creation of XML Web services that would link systems that fed data, for example, about vehicles, fingerprints, insurance, number plate recognition and names. Hu said Wednesday at XML Conference 2004 that he and his team componentized each of these applications into Web services that could be called through a standard interface.

"The way to do this was wrap them as one component, stick a WSDL (Web Services Discovery Language) on top of it and publish it as a Web service -- and the other systems can consume those services," Hu said. "The adapters convert the lexis system into XML as requested by the Web service."

Hu's team had to create their own XML interface and message schema standard, he said. Standardizing the document-centric messaging model simplified creation of the services and the transfer of data between those services.

Service-oriented architectures are reliant on quality XML data representations, said Thomas Erl, chief architect with XMLTC Consulting Inc. of Vancouver.

"SOA requires data representations and service modeling standards be in alignment," Erl said. "The granularity of the service interface must align with the XML document."

XML documents must be payload-centric, Erl said. The WS-* (WS-Security, WS-Policy, WS-Trust, WS-SecureConversation and WS-Federation) set of standards, for example, assumes a developer is working on a document-centric model.

Erl recommends enterprises design for the WS-* standards.

"It's good to be aware of your enterprise logic and what you want to realize in your environment, and the standards that would make that happen," Erl said. "Get familiar with the standards, even if they're not mature."

Some of the standards Erl pointed out include BPEL4WS (Business Process Execution Language for Web services), WS-Addressing and WS-Reliable Messaging.

SOA, meanwhile, is championed as the premier integration strategy for the enterprise today.

"SOA doesn't make distributed computing easier -- it's adds to the complexity to the extent that the Web services standards are not mature yet in vendor products. But once SOA is standardized," Erl said, "building solutions becomes easier. A good portion of development becomes more modeling than coding using components."

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