Wow, Google is releasing lots of code into the open source comunity! Protocol buffers are just another example! With all their downsides they still are my favorite idl, think about fast and efficient binary encoding and blazing fast decoding using binary string representations, still not convinced? C++, java and python generated classes with nice looking accessors for all the fields you might want to provide.

Get them while hot: http://code.google.com/apis/protocolbuffers/docs/overview.html

dArio