Via this post on Stefan Tilkov’s blog, I found an interview that Stefan did with Jim Webber about SOA and MEST – a message-centric approach to SOA. You can watch it here. I don’t often watch this sort of thing, because I prefer to read the transcripts – in addition to being able to read faster than anyone I have met or seen can talk, I can read the interview in a way that suits me (e.g. going back and re-reading an answer.) However, I made an exception in this case, and I’m glad I did. One interesting observation made by Jim Webber, which rings true, is that relying or being dependent on a big SOA platform increases coupling – with the resultant increase in inertia. I like the idea of the “letterbox” being the service interface – the letters being messages that are defined by a schema or equivalent in a transport-agnostic way. What is left unanswered in this interview is what to do when you need a near-realtime response (e.g. a query.) It is very easy in these instances to adopt an RPC style, which is a style you should be avoiding in building an SOA. At the moment, I tend to favour forward caches in these instances (i.e. the system of record uses a pub-sub paradigm to disseminate its data.) While this simplifies the message definitions and allows a lot more flexibility in how to use the data, it does have the disadvantage, of course, of a proliferation of data.