Can WSDL be used to describe RESTful Web services?
An on-going area of interest has been REST vs. SOAP/WSDL, such as Web Services: REST vs. SOAP/WSDL. In general, REST and SOAP/WSDL have been seen as two very different approaches where you had to choose one or the other because never the tween shall meet.
Now I've stumbled upon "Describe REST Web services with WSDL 2.0" (developerWorks), which explains that "Until recently there was no formal language to describe REpresentational State Transfer (REST) Web services-now there's WSDL 2.0." It's by Lawrence Mandel, who works in IBM Rational and leads the Apache Woden project (which is developing a WSDL 2.0 parser). Looks like WSDL 2.0 is becoming an alternative or replacement for WADL.
The article also has a handy sidebar, "What's changed in WSDL 2.0?."
If you're using REST and would like to be able to describe the interfaces, WSDL 2.0 may be just what you need.