Radovan wants OCL for web services (or more precisely, he wants a Service Constraint Language). I do too. As far as I know, a variation of the Object Constraint Language doesn't exist - let's call it SCL.
But be careful, just because you define constraints (pre-conditions, post-conditions, message verification - and potentially even the order of service participants), you haven't created a replacement for a fully defined business process. I love constraints - and I love fully described digital business processes - and I really love when the two are combined.
I've been having some offline conversations on the 'coupling index' - a means to quantitatively determine a 'loose or tight coupling factor'. One thing I noticed is that by having a centrally defined business process, we are able to have more fully encapsulated services (we shift knowledge out of the service and into the process). However, I've also noticed that the current state of web services fails dramatically in being 'fully encapsulated' - mostly due to the lack of constraints put on the operations. That is, a significant amount of knowledge beyond the interface is still required.
And yes, if we wanted... we could build an SCL as a web service... which means we could orchestrate the pre- and post condition calls. :-0 (not that you would want to... I'm still in that mode where everything looks like an orchestration...)
p.s., I'm a fan of point-to-point integration as well!