Chapter 2. XML Schema and the SOA Data Model


XML is the lingua franca of SOA. It is used for message payloads, application configuration, deployment, discovery, runtime policies, and increasingly for representing executable languages such as BPEL that are central to the SOA landscape. Web service interfaces are represented with XML in the form of WSDL, and XML is used as the chief data transport mechanism in SOA. Because XML is so inextricably linked with web services development, and because its inherent flexibility and expressiveness make it so powerful, it’s a natural fit for designing your data model for use within a SOA.

Designing data models as XML provides you with a valuable implementation-independent foundation. It frees you to focus greater attention on ontology (the determination of what exists), and to be less subjected to vendor constraints. Because the libraries have at once become more sophisticated and easier to use, XML is more attractive than ever as a place to start working with data models for your SOA.

Pundits and artists alike have long pointed out that our use of new communications devices—whether cell phones, texting, IM, email, or PowerPoint—does not merely change how we communicate, but inevitably must augment or rearrange fundamentally what we communicate. Marshall McLuhan summarized this in 1967 as “the medium is the message,” meaning that the form of a message will subsume the ostensible content of the message itself. As an architect, it’s ...

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