WADL, WSDL, XSD, and the Web

More interesting fodder on Stefan Tilkov's blog, this time on whether RESTafarians need WSDL-like functionality, potentially in the form of WADL.

Several points come to mind.

First, I'm doubtful that WADL will be substantially better than WSDL given the reliance on XSD to describe XML payloads. Yes, some of the cruft WSDL introduces goes away, but that cruft wasn't where the interop probems were lurking.  I know WADL allows both RNG and XSD - I have no idea what the state of RNG import/export machinery looks like for Java (or Python or Ruby).  I'd love to hear of people's experience using RNG importers for their programming language of choice.

Second, I think Stefan goes a bit too far when he states (in comments):

“Due to the tight coupling usually created by stub and skeleton generation, I do not advocate this at all. “

Ultimately folks who use languages with dots (e.g., Ruby, C#, Javascript) or with slashes (XPath, XSLT, XQuery) often make assumptions about the “shape“ of the messages they process. At MS, we've built “dot-based“ programming models over XML that are liberal in what they allow, but ultimately if a user depends on access to an element named “foobar“ that element needs to be in the XML whether the user is using dots or slashes. Yes, people can program around missing/optional data (thank God for null), but again, most programs that consume XML make some commitment to element and attribute names that wind up being an intrinsic part of the definition of the program (even when those parts of the program are stored out of band from the code stream (e.g., attributes)). 

Finally, I think there's a lot of merit to what Erik Johnson states in Stefan's comment area:

“It seems to me that people attracted to REST (in whatever form) are rebelling against interface-based programming more than WS-* itself — at least that’s my excuse.“

Now that Orcas is in the shute, we're looking at how/if to support UriTemplate in WCF metadata. We'll likely do it for users who expect that functionality, but we're not confused at all that a BIG part of the attraction to folks is opaque URIs and no metadata and are committed to making that work exceedingly well.