I’m not too sure about all this “manifesto” stuff these days. Certain right-wing politicians from days gone by are surely rolling in their graves. Then again, today’s highly communist/socialist oriented open source worldview would have gotten many of us into a lot of trouble just a few decades ago…
Regardless, there’s now the SOA Manifesto. And it seems to capture the spirit of SOA in a concise manner.
In fact, its opening statement, talking about putting business value above technology and so forth, seems to make sense for any software endeavor, not just ones that are service-oriented.
If you consider that SOA is much more of an enterprise architecture than it is an application architecture, this all makes a great deal of sense. The idea that applications should use service-oriented communication when they need to interact with each other is exactly the sweet spot for service-orientation.
In that context, saying things like external uniformity and internal diversity are good is clearly correct; because different applications may require different technologies or implementation choices, but they all need to work with some enterprise-standardized message-based service model.
I still suspect SOA may ultimately make a big difference in our industry. But I also think it will take decades to do so, just like object-orientation. People were working on object-orientation for well over 20 years before the ideas became mainstream. SOA is (if you are really generous) maybe a decade old, so it is probably time to work on some formalism so it is ready to become mainstream 10-15 years from now :)