Web Application Description Language (WADL)

Sun has submitted "Web Application Description Language" (WADL) spec to W3C.
It's a desription language analogous to WSDL, but for REST/API services. It's also supposed to describe relationships between the resources.
See http://www.w3.org/Submission/wadl/

Implementation: There is a current implementation of it as part of Jersey JAX-RS.

An Amazon service in WADL is represented as

 1 <application xmlns="http://wadl.dev.java.net/2009/02" 
 2   xmlns:aws="http://webservices.amazon.com/AWSECommerceService/2005-07-26" 
 3   xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
 4   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 5   xsi:schemaLocation="http://wadl.dev.java.net/2009/02 wadl.xsd"> 
 6 
 7   <grammars> 
 8     <include href="AWSECommerceService.xsd"/> 
 9   </grammars> 
10 
11   <resources base="http://webservices.amazon.com/onca/"> 
12     <resource path="xml"> 
13       <method href="#ItemSearch"/> 
14     </resource> 
15   </resources> 
16 
17   <method name="GET" id="ItemSearch"> 
18     <request> 
19       <param name="Service" style="query" 
20         fixed="AWSECommerceService"> </param> 
21       <param name="Version" style="query" fixed="2005-07-26"> </param> 
22       <param name="Operation" style="query" fixed="ItemSearch"> </param> 
23       <param name="SubscriptionId" style="query" 
24          type="xsd:string" required="true"> </param> 
25       <param name="SearchIndex" style="query" 
26          type="aws:SearchIndexType" required="true"> </param> 
27          <option value="Books"/> 
28          <option value="DVD"/> 
29          <option value="Music"/> 
30 
31       <param name="Keywords" style="query" 
32         type="aws:KeywordList" required="true"> </param> 
33       <param name="ResponseGroup" style="query" 
34         type="aws:ResponseGroupType" repeating="true"> </param> 
35          <option value="Small"/> 
36          <option value="Medium"/> 
37          <option value="Large"/> 
38          <option value="Images"/> 
39 
40     </request> 
41     <response> 
42       <representation mediaType="text/xml" 
43         element="aws:ItemSearchResponse"/> 
44     </response> 
45   </method> 
46 </application>

Would like to hear your comments on whether you find this spec useful. Currently, it doesn't have a security profile. What would you like to see defined in such security profile?