This is probably only relevant and interesting for folks interested in a custom query parser (e.g. for a WIQL Linq Provider), but in case you’re in that particular group, it might be nice to know that the syntax specifications of TFS’s work item query language (WIQL) is in fact available in the Extended Backus Naur Form (EBNF) format definition at MSDN.
This is only available in the TFS/Visual Studio 2008 documentation, but as far as I can tell this hasn’t changed in more recent versions (2010 & 2012). However, if it turns out to have changed as I dig deeper, I’ll update this post and let you know.
As it turns out, the TFS2012 Wiql page now contains the EBNF syntax, again. It still does not contain the restrictions and differences to the Testmanagement store but good nevertheless.