SharePoint query-language... documented...!
I feel bad for blaming Microsoft for having no documentation on the dsQuery language… its there: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/spptsdk/html/soapmqueryRequest_SV01071735.asp. Click through on the keywords and you end up in the CAML keywords…
Reyn wrote even some piece of code to generate these queries in an easy way from C# code. See his weblog entry at http://dotnet.org.za/reyn/archive/2004/07/13/2738.aspx, and the code download at http://www.reyn.co.za/index.php?pr=SP_Query_Builder.