Q&A with Mark Colan Evangelist, SOA and Web Services: IBM Corporation
Q: What is the relationship between SOA and Web services; SOA and grid computing?
A: SOA is an architectural design style for business application systems, but it can be applied to other systems, including middleware technologies like grid computing.
Web Services is a set of standards that can be used to create a Service Oriented Architecture. While is possible to create SOA without the Web Services standards (for example, people have used XML over HTTP or JMS to achieve a similar result, before the SOAP standard), for interoperability with external software the use of Web Services standards is the best approach we have today.
Grid Computing is a system management strategy whose goal is to maximize the use of hardware resources. For example, when unexpected demand floods the designated server, it could be possible to direct some of the requests to a less busy server on a temporary basis. Grid computing is designed as a Service Oriented Architecture; in particular the services used to coordinate Grid Computing are called Grid Services.
As we move forward with SOA, we will see this approach used to support a variety of other new systems features. Autonomic computing, or self-managing systems, is another example. In fact SOA is the basis for advanced capabilities in Web Services, such as the WS-Trust and Federated Identity Management specifications.
Q: Isn't the biggest problem of SOAs still vendor-centricity since there are no universal interoperability standards yet?
A: The basic standards are in place for Web Services, and these can be used to implement a service-oriented architecture. XML and XML Schema have been standards since 1998 and 2001, respectively. SOAP 1.2 has been a standard since June 2003. UDDI was standardized in summer 2003. WS-Security became a standard in April 2004.
Aside from these official standards supported by well-known standards bodies such as W3C and OASIS, many "technology proposal specifications" are well accepted and well supported as interim "de facto" standards. For example, until WSDL 2.0 is finished at W3C, the WSDL 1.1 specification is supported by most vendors who claim Web Services support in their products.
Indeed the support we have today for Web Services standards from major software vendors has lead to widespread implementation of SOA using Web Services. IBM has several hundred customers who have successfully completed prototypes or have Web Services in production already.
Q: How do SOAs impact SLAs? And how do you adapt SLAs to your SOA?
A: Today's SOA implementations between companies typically focus on improving efficiency of existing business between partners. As such the notion of performance guarantees is not as much of an issue as easy interoperability and loosely-coupled integration, which can be achieved with Web Services standards.
A guarantee of a particular level performance or availability, and other quality of service considerations, comes into play more when service use becomes a product that companies pay for. We can imagine this becoming a common requirement in the future, and work is underway to support this model.
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