Dispelling Some Web Services Myths, Part 1

Computerworld - I'd like to briefly expose a few prevalent Web services notions that may be slowing the adoption of Web services and SOA. This will be a multipart series, so let's begin Part 1.

What is a Web services architecture (WSA)? What is a services-oriented architecture (SOA)? Are they the same thing?

There is confusion in the field about the meaning of these two terrms. I often hear both phrases used, sometimes interchangeably. What is the difference and why should it matter?

It certainly is possible to implement Web services in a non-SOA fashion, and this might be considered a Web services architecture. This is common for integration-focused Web services that are used to replace proprietary enterprise application integration (EAI) or homegrown integration approaches that are inflexible and expensive to maintain.

Similarly, a SOA can be implemented without deploying Web services, and in fact it has been done in the past with solutions such as Common Object Request Broker Architecture, Distributed Computing Environment, Component Object Model/Distributed Component Object Model, and even more recently with Java 2 Enterprise Edition middleware abstractions. These implementations were limited in that they were tightly bound to the computing platforms for which they were designed.

In general, an SOA is an architecture where application functionality is available as shared services discoverable on the network. Key elements of this SOA definition are "shared services" and "discovery." When a SOA is implemented using Web services , it's a more flexible and standards-based architecture than SOA without Web services. In fact, many industry proponents argue that Web services are an excellent architectural means to implement SOA based on Web Services Description Language (WSDL) as a superior Interface Definition Language (IDL) than previous approaches to SOA.

In a Web services-based SOA, available services are exposed using industry standard XML-based interfaces and communication mechanisms such that they will operate across all technology platforms. This is a superior architecture than SOA without Web services.

A Web services-based SOA is likely to employ all four core standards of Web services: XML, WSDL, Simple Object Access Protocol (SOAP) and Universal Description, Discovery and Integration (UDDI). In addition, the SOA implementation of WSDL to describe the available services will be such that the services will support dynamic binding and services reuse, where the WSDL in a WSA will probably employ static binding and may not be as easily incorporated into a future SOA without rework.

As mentioned above, Web services can be implemented in a non-SOA manner. Internal integration services are often implemented initially as point-to-point