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wadl.rb: If you like REST web services I have something for you. A while ago Marc Hadley came up with a service description language called WADL. I now have a primitive proof-of-concept Ruby WADL parser/client that can read a WADL file and call simple web services like the Yahoo News search. (I emboldened that link because there are so many other links in this entry, and that's the one this entry is about.)

Right now every REST web service is slightly different. You access them all with simple tools: your language's HTTP library, and probably its XML parser. Which is great because it keeps the services simple. What's not so great is that you have to learn each REST service separately.

What's more, it's useful to package and distribute your implementation of a particular service in a particular language. There's PyAmazon and Ruby/Amazon and a4j, PySearch and Yahoo-Ruby. That's always seemed wrong to me.

With a SOAP/WSDL service you just load up the WSDL file and call or generate the native language methods. Even though the underlying technology has more layers and is much more complex, when WSDL is one of those layers (and nothing goes wrong), everything just works. Sometimes there are language-specific wrappers on top of a SOAP/WSDL service (PyGoogle and Ruby/Google), but they don't do much: they make your code look nicer, or compensate for the shortcomings of the underlying API.

WADL is the best way I've found to get that ease of use for REST services, without creating documents that don't make sense to humans, or selling out the resource-oriented architecture of the web. WADL is very human-readable and it describes resources, dammit. I like it a lot and I think it'll make things easier for programmers if it gets widely adopted.

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