Web Services Security and More, Part 2: The Global XML Web Services Architecture (GXA)

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Message Information Headers

In an effort to promote more flexible and dynamic exchange of endpoint information in tightly coupled environments, WS-Addressing defines a family of message information headers that enable uniform addressing of messages in a transport-neutral way. These message information headers convey end-to-end message characteristics, including addressing for source and destination endpoints and message identity. The following are some of the properties that message information headers contain:

• Destination: A URI that is the address of the intended receiver;
• Recipient: The ultimate receiver of the message;
• Source Endpoint: The endpoint from which the message originated;
• Reply Endpoint: The intended receiver for replies to the message;
• Action: A URI that uniquely identifies the semantics implied by the message (recommended to correspond to an abstract WSDL construct such as a message, operation, port type, and so forth that is available at the destination endpoint);
• Relationship: Used to correlate a response message to the message to which it is responding;

The following example illustrates a set of message information headers:

      <S:Header>
    <wsa:RelatesTo>uri_of_another_message</wsa:RelatesTo>
    <wsa:To>http://www.someendpoint.com</wsa:To>
    <wsa:Action>http://www.someendpoint.com/ProcessMessage
    </wsa:Action>
    <wsa:From>http://www.somesender.com</wsa:From>
    <wsa:ReplyTo>http://www.someendpoint.com/user9876</wsa:ReplyTo>
    <wsa:Recipient>http://www.someendpoint.com/user1579
    </wsa:Recipient>
      </S:Header>

The following table cross-references the properties presented above with the element names in the above example:

Property	Element Name
Destination	To
Recipient	Recipient
Source Endpoint	From
Reply Endpoint	ReplyTo
Action	Action
Relationship	RelatesTo

Specification Location

The WS-Addressing specification can be found at msdn.microsoft.com/ws/2003/03/ws-addressing.

Conclusion

In this article, we have discussed the Global XML Web Services Architecture (GXA). GXA is poised to play a major role in advancing the adoption of Web services through its robust specification of mechanisms for Web services such as security, policy, coordination, federation, and routing. More specifications will be forthcoming for areas such as privacy, federation, and authorization.

About the Author

Joseph Chiusano is a Senior Consultant with Booz Allen Hamilton. His technology background includes such diverse areas as systems architecture, relational database applications design and development, operating system development, and XML consulting. Joseph possesses in-depth knowledge in many aspects of XML and XML-related technologies, including Web services, XML schemas, digital security, XML registries, and XML vocabularies.

Endnote

1 WS-Coordination will not be covered because most aspects of the WS-Coordination specification were covered in Part 1 in describing WS-Transaction. DIME and WS-Attachments will also not be covered, for reasons stated in their sections.

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