David
Noller defines Web Services as the means by which applications can
provide standardized access over the Internet or intranet to the
functions available in the applications. Noller, the Blacksburg, Va.-based manager of automotive solutions with IBM Software Group’s Industrial Solutions Development group (www.ibm.com), adds that Web Services can be used as a single interface or be composed into flows to implement more complex business logic.Extensible markup language (XML) lies at the heart of these services, which are available via hypertext transfer protocol (HTTP) interfaces through XML-based simple object access protocol (SOAP). “Information is exchanged between applications using Web Services such as XML documents,” Noller says. The service has to have a Web Services description language (WSDL, an XML format) “advertisement” that can be accessed by other programs at universal description, discovery and integration (UDDI) registries, adds Dr. Venu Vasudevan, manager of pervasive platforms and architectures within the applications research group of Motorola Labs (www.motorola.com), in Schaumburg, Ill. He adds that the practicing Internet community has simplified and broadened Web Services to include XML over HTTP, a combination known as Representational State Transfer or REST. Web Services combine with XML as the current foundation for service-oriented architecture (SOA). It can be used to implement business processes spanning applications and people within a company and across a company’s supply chain, Noller explains. Standards assistHe says those SOAs comprise an area in which vendors, standards bodies and industry organizations collaborate to assist manufacturers. For example, IBM initially worked with BEA Systems, Microsoft and others to develop standards for XML, SOAP, Web Services and business process execution language (BPEL) for Web Services, Noller recalls. “Now, to provide even better support for treating applications as components that provide services, IBM is working with BEA, SAP, Iona, Oracle and others on emerging standards for Service Component Architecture (SCA) and Service Data Objects (SDOs).”Some view SOA, Web Services and XML as means of interoperability, Noller says. Where performance is a major issue though, binary alternatives to XML exist and are supported, he adds. For example, OPC-UA, the OPC Foundation’s Unified Architecture for interoperable communications, supports both XML/Text and UA/Binary, he notes. Regarding other new or modified applications of XML and object technologies that support manufacturing, Vasudevan mentions the “XMLization”—or XML-based standardization—of global information dissemination technologies via really simple syndication (RSS); Atom, for Atom Syndication Format, an XML language used for Web feeds; and Atom Publishing Protocol (APP), an HTTP-based protocol used to create and update Web resources. These have shaped media and information-services industries, he says.And of the XML technologies and objects integral to Web Services, Vasudevan believes the most important is the suite of open platforms consisting of the Apache Web Server, Javascript and XML. “This has become a compelling enough de facto platform to warrant its own acronym, AJAX (asynchronous Javascript and XML),” he says. A low-cost platform, AJAX is important for so-called Web 2.0 enterprises offering wide-area services that need to scale globally, he notes. What’s on the Web Services horizon? Noller suggests standardization and adoption of a semantic definition of the Services. That will help move Services to more of a plug-and-play model, he believes. Regardless of the future, these Services now are the de facto mechanism for integrating large, loosely coupled systems into “systems of systems,” Vasudevan declares. “As Services scale globally within and across enterprises—for example, collaborative commerce—Web Services and AJAX remain the only widely adopted solution.” C. Kenna Amos, [email protected], is an Automation World Contributing Editor.
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