Head over to Ryan Tomayko for an excellent summary of the debate over REST and IDL:
WSDL is basically every bad idea anyone ever had related to service documentation/description, schema, and/or discovery all rolled nicely into a document classified as a “recommendation”.
I picked on this particular sentence because to me it sums up the discussion in a nut shell. We do need an IDL, or maybe more than one, I’m not seeing evidence to the contrary. But we’ve all been burned by the horror that is WSDL, and the particular way people use it to do RPC over HTTP, that we’re cautious to try again.
Some took the lesson from WSDL that a service description language is only good for generating revenue from licensing ever more complex products. I took a different lesson.
That you start by solidifying the ideas of what you want to express, before deciding how to express it. Best practices should come before arguing RDF vs JSON and elements vs attributes.
The Atom Publishing Protocol specification is an IDL for a specific type of service. It happens to use a well known service definition language, called English, which unfortunately is not very tooling friendly. But it packs a lot of best practices. A good IDL would let you describe APP fully and precisely.
What we need is a few more Atoms, a big enough set we can use to distill ideas and decide what — not how — we need to capture in that IDL. Writing a language, or several languages, from that is an easy deal.
Otherwise, the temptation to create a language that has concise form in JSON but lacks important features, or is semantically rich in RDF but follows the wrong practices, or uses Microformats but only on Sundays, is too overwhelming. In all that syntax, it’s hard to see the semantics.
So far most of the suggestions I saw are turf wars in disguise, arguing for this syntax or that, but never for what it should describe. WADL so far looks like one of those best-for-my-platform choices, the constant mentioning of Microformats, which are not optimized for this task, is another danger sign.
It has to start somehow, but it better start with substance, not with style.
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