Tim Ewald responds (along with a few
others) to my previous post
about WSDL and states: ”Remember that WSDL/XSD/Policy is the contract,
period. Any other view of your contract is just an illusion.”
WSDL and XSD and Policy are interoperable metadata exchange
formats. That’s just about it. The metadata that’s contained in
artifacts compliant with these standards can be expressed in a multitude of different
ways. I do care about “my tool” (whatever that is) to do the right
thing mapping from and to these metadata standards whenever required and I do
care about “my tool” guiding me to stay within the limits of what
these metadata formats can express.
But WSDL/XSD/Policy isn’t the contract. If you do
ASMX, you can create server and client without you or any of the tools ever
looking at or generating WSDL. And it works. If you use Indigo, you can do the
same and, in fact, for generating any XML-based metadata from within an Indigo
service, it’s even required to explicitly add the respective service
behavior at present. The required metadata to make services work comes in many
shapes or forms and is, for a given tool, typically richer than what you will
find in the related WSDL/XSD/Policy, because not all that metadata is related
to the wire format itself.
If I need to tell someone who is not using my tool of choice
how to talk to my service, I have my tool generate the respective metadata
exchange documents and I want to be able to trust my tool that they’re “right”.
What I am stating here is simply my demand and expectation
for the degree of “automatic interoperability” that I expect from
the tools. I can read WSDL/XSD/Policy; out there, most people absolutely don’t
seem to care about these details and I tend to agree with them that making this
stuff work is someone else’s problem.
I don’t need to be able to read and write PDF to use
PDF. I use PDF if I know that someone will open my document who is not using Microsoft
Word. Still, that PDF doc isn’t the
document. My Word source document is the document
I edit and revise. The PDF is just one of several possible representations of
its contents.