OOPSLA’07 – SOA and Web Services

After arriving in Montreal Saturday evening, on my first day at OOPSLA, I attended the Fifth International Workshop on SOA & Web Services Best Practices. The workshop consisted of a couple of keynote talks, presentation of papers, and group work.

Olaf Zimmermann stepped in for Ali Arsanjani, giving a keynote on SOA. One of the things he talked about was three central patterns that are central for SOA, namely

  • Service composition
  • Registry
  • Enterprise Service Bus

So, I guess if you have none of these in your architecture, you are not doing SOA. 😉

The second keynote of the day was given Gregor Hohpe, author of the seminal book Enterprise Integration patterns. He talked about the usage of patterns in general, and in the context of integration and SOA in particular. One of the points he made was that the “WebMethod” approach to making services is flawed in the context of SOA. It is certainly buzzword compliant, but that’s all. (By “WebMethod”, I refer to the approach where you declaratively annotates your existing class to generate a Web Service interface for it)

Gregor went on to talk about design patterns in general, and summarized the aspects of design patterns:

  • They are “Mind sized” chunks of information (attributed to Ward Cunningham)
  • They are used for human-to-human communication
  • They express intent (the “why” vs. the “how”)
  • They are observed from actual experience
  • They do not firm a rule (rather guidance)
  • They are not copy-paste code

He also made a point that sketches are important in patterns. However, it should be emphasized that
sketches should not be mistaken with blueprints. Furthermore, he made a point that patterns could effectively be used to test products/frameworks by testing to see that the product or framework could cover design patterns.

Yet another point made (which I think makes much sense) was that declarative programming brings you further away from the execution model, which makes it hard to understand what’s going on, and harder to debug since the the execution path is chosen at run-time. Certainly something to think about, as we see
the use of declarative programming (through annotations in Java, attributes in .NET, XSLT, and various

rules engines) is growing.Looking at SOA and integration in general, Gregor went on to point out that SOA means event-based, asynchronous programming, or “programming without a call stack”. Furthermore, he warned about trying to “program in pictures”. Looking at pictures to understand the architecture is OK, but trying to program pictures brings on problems like scalability, lack of support of diff and merge, etc.Another part of the workshop consisted of group work, where various topics around SOA and web services were discussed.
One of the most important point I think was that we should strive for simplicity in SOA. As vendors bring on more and more products, we should really look at how we can scale down solutions, and make middleware simpler.