Don Box...
To anticipate Patrick's comments, I'm a huge fan of minimal kernels of abstraction (like lisp) upon which we define entire universes.
SOAP is minimalistic enough for me - it's sad (but not terminal) that SOAP's defun, WSDL/XSD, is as complicated as it is.
Had we started with a simpler basis (perhaps Relax NG + some SOAP-specific extensions), my guess is we'd be having different discussions right now.
This seems to be arguing about syntax, more or less. I think the more interesting argument is about semantics. In particular, the semantics of coordination.
Looking for a minimal *coordination* kernel (a machine) upon which we define entire *coordinated* universes, SOAP is merely a syntax for defining the right machine primitives. SOAP is a general purpose *language* kernel. We still need to define the machine kernel, whether we use SOAP or something other language to describe it.
What would make a good coordination machine kernel?
It should have enough primitives to be useful for the simplest cases. Those primitives should be fixed and yet composable for most of the interesting, complex cases.