Jon Udell is talking about an architecture of intermediation. Its interesting that Web services intermediaries became sophisticated very quickly (some might argue too quickly) while RESTful intermediaries have pretty much offered store and forward services 'ala proxies and little else. Jon's positing that that should change. I think he's right. This is right in line with the call for better tools and standards for RESTful Web services that I made a while back.

The reason I link more sophisticated intermediation and better service description standards for RESTful services may not be immediately obvious. Over the past two years, I reviewed a lot of intermediaries for SOAP. They are made usable by WSDL. Without WSDL, using one of these would be such a chore, that you're never do it. Every time you wanted to configure a new service intermediation, you'd have to custom describe the API. With WSDL, I just give the intermediary the URL for the service's WSDL file and it configures itself. That's powerful and makes these things relatively easy to use.

Some, like Stefan Tilkov disagree that we need a description language for RESTful services, on the basis that description and strong (or static) typing are somehow linked. I don't buy it. I believe that API descriptors are a powerful tool for interoperability, even when the language or service is dynamically typed. Without it, you severely limit the kinds of intermediation that you can do.