WSDL, JSON-WSP[1], now protobuf, and many more formats abound on the web.

In the spirit of 'choose the boring technology', which of these[2] is common enough / flexible enough to be worth learning to use and use well for non-fad web development / homestyle programming?

I'd default to WSDL since I happened to grow up learning that in school, but I'm sure that's my baby duck syndrome since CORBA etc came before that.

[1] https://en.wikipedia.org/wiki/JSON-WSP

[2] https://en.wikipedia.org/wiki/Interface_description_language