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Revised Feb 23 2009: will get more attention in coming months

A year ago, the subject of Semantic Web Services might have been considered visionary. In fact, several of the early corporate efforts were canceled or abandoned ( such as Microsoft's GoDotNet ). At best, the technolgy has been static.

But that is not the case today. Several popular web development tools and packages ( such as the Drupal Services project ) are making the vision a concrete reality.

Note: moved from the Development site Sept 24 2008. small edits

The Oasis standards organization published a Reference Model for SOA ( Service Oriented Architecture ) not too long ago. In it, they compared SOA and OO ( Object-Oriented ) technologies. While I don't agree with them entirely ( or even mostly ) on the strengths and weaknesses of SOA versus OO technology, here is an extended quote of what they have to offer on the subject.

One of the hot areas for cross-fertilization these days is business rules and service oriented architecture.

Business rule and object technology veteran Ian Graham has written an excellent book on the subject titled Business Rules Management and Service Oriented Architecture: A Pattern Language.

Revised Sept 7-12 2008: Added IBM and many other links

This site is primarily about open source solutions, so the honor of precedence goes to the Open SOA Collaboration. The organization is not very active, but it moves along over time.

From the home page:

The Semantic Grid takes the standards of the Semantic Web usch as RDF and OWL and combines them with the technology of Grid Computing, sometimes called the Computational Grid. There is a strong association between Grid Computing and SOA architecture.

One of the best descriptions from the article Semantic Grid is Laying the Foundations for the Semantic Grid (PDF ):

Joe McKendrick capitalizing on service-oriented architecture, but interesting articles nonetheless.

Why the SOA Reference Architecture ?

The OASIS SOA Reference Architecture is one of the best introductions to SOA, providing a complete, consistent and largely non-technical set of concepts and definitions for SOA technology. It may be the easiest way to understand SOA without digging through volumes of arcane technical standards and XML specifications.

The OMG ( Object Management Group ) is a consortium that sets standards for object-oriented systems and and model-based architectures.

Perhaps the most interesting page from a standards standpoint is the SOA Glossary.

The SOA glossary, provided by the SOA Community of Practice, contains general definitions of SOA terms as well as links to common definitions in industry and standards organizations such as OMG, Oasis, Open Group and W3C.

The spec for the SOA Reference Model includes a very good discussion of the differences between the SOA approach and an OO ( "Object-Oriented" ) approach to web services, although strictly SOA is not about web services. In their definition, SOA is "a paradigm for organizing and utilizing distributed capabilities that may be under the control of different ownership domains". Sounds a bit vague to me, but it may be the clearest definition to date.

In IBM's tutorial on Web service design patterns, they use several concrete examples of XML messaging. The result is interesting.

Consider one of the XML messages used in the example: