What Leonard Said
I've been offline on holiday in the UK for the last couple of weeks and it seems I've been missing out on an interesting debate about whether a description language for RESTful services is useful or not. The debate so far is nicely summarized by Arnon Rotem-Gal-Oz in Debate: Does REST Need a Description Language?.
Obviously as the author of the WADL specification I think there is some utility in such a language and normally I'd be tempted to write a longer post addressing some of the points raised but rather than do that I'll instead direct you to Leonard Richardson's It's Just A Hypermedia Format which covers most of the things I'd have said had they not already been expressed so well.
One thing I would like to add since many people are concerned with the link to XML schema: the element attribute of the WADL representation element is optional; WADL can use XML schemas but it isn't built on them. In fact WADL doesn't presume XML will be used for entity bodies and it can easily describe an application built using other media types.