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Standardizing Web Services Communication
W3C receives WS-Addressing spec to mark another step forward in giving enterprises the ability to build interoperable Web services

September 6, 2004

The latest version of WS-Addressing, an important Web services specification, was recently submitted to the World Wide Web Consortium (W3C) for input into the standardization process by coauthors BEA, IBM, Microsoft, SAP AG, and Sun Microsystems (see the sidebar, "WS-Addressing Collaborators"). The collaborative submission demonstrates a landmark effort to move Web services technology forward and has significant support from the industry. It represents a long-term endeavor to provide a standards-based foundation for developing asynchronous, reliable, secure, and transacted Web services by defining a standard mechanism for identifying and exchanging Web services messages between multiple end points.

WS-Addressing facilitates the exchange of data between disparate types of software applications to allow systems to support the transmission of Web-service messages. The standard provides for explicitly defining information in the SOAP header for Web service calls rather than relying on HTTP for its transmission, which gives developers better control over how response messages from Web services calls are handled, and allows TCP to be used as the means for invoking Web services. The objective behind WS-Addressing is to identify Web services in a manner that is similar to identifying Web sites by IP addresses or URLs, which would ultimately provide an easier mechanism for routing requests. Not only will such an approach provide flexibility for handling responses, it will also allow for combining Web services and customizing the handling of SOAP faults.

WS-Addressing defines two interoperable, transport-neutral constructs—end-point references and message information headers—that transmit information typically provided by transport protocols and messaging systems, according to Microsoft Developer Network documentation (see Resources). End-point references provide the information necessary to access a Web service end-point and addresses for individual messages sent to and from Web services. The specification defines a family of message information headers that permit uniform addressing of stand-alone messages that are separate from the underlying transport. The message information headers transmit end-to-end message characteristics, which include message identity and addressing for source and destination end-points. By design these constructs are extensible and reusable.

Dave Chappell, chief technology evangelist at Sonic Software, admitted to "feeling very positive" about the specification in a recent blog entry and said that most of the other Web services specifications rely on the addressing concept. According to Chappell, WS-Addressing specifies interoperable end-point references in the form of SOAP header information that defines where messages are from, where they should go, and where to send them when they are bad—specifically, headers such as MessageID, From, To, ReplyTo, and FaultTo (see Resources).

Among the specification's collaborators, SAP and Sun were the latest to sign on. Sun had, along with other companies, submitted a competing Web services addressing specification—WS-MessageDelivery—earlier in the year. Following the recent rapprochement between Sun and Microsoft, however, Sun switched its allegiance to WS-Addressing, primarily because the company recognized that customers wanted a single specification and identified WS-Adressing as the one garnering the most market momentum, according to Ed Julson, director of Web services marketing for Sun. Sun has stated that it plans to support WS-Addressing in products that are part of its Java Enterprise System, and Julson said that during the W3C process Sun and the other WS-MessageDelivery backers will provide feedback on the WS-Addressing specification in an effort to move toward a single addressing standard (see Resources).

SAP has reported that it will support WS-Addressing in a future version of its NetWeaver product. According to Marc Goodner, a technology architect at SAP, the company views the specification as an important step in helping reduce the complexity for customers. BEA, IBM, and Microsoft will also support WS-Addressing in their products, according to reports from their company representatives.

This collaborative submission effort points up how WS-Addressing should be a key part of the core Web services architecture, and the specification is designed to underlie other specifications, such as WS-ReliableMessaging, WS-Federation, and WS-AtomicTransaction. It demonstrates the coauthors' commitment to open industry standards development and to move another step forward for the widespread adoption of Web services. The coauthors reportedly will not charge royalties in conjunction with WS-Addressing to ease adoption, and they look forward to future collaboration to foster a cohesive Web services architecture.

Several resources were consulted in putting together this report. For more information, go to the online version of this column at www.javapro.com and follow the link to its Resources.

Terrence O'Donnell