At this point, I believe most SOAP plumbers have conceded that XML
Schema will be the dominant type system and metadata format for interop.
How one converts from their local type system to the world of XML Schema
is a local problem that is (and should be) outside the scope of SOAP.

In MSFT-land, we do the conversion by importing XML Schema into our
runtime and making the "foreign" types look local. That technology is
broadly useful outside the scope of SOAP and/or web services, so we make
it accessible everywhere, although I'm sure there are lots of customers
who have no idea this is even in the platform.Link