Query Languages Report "A report by AIFB and Sesame and Jeen Broekstra from the Sesame crew. The Authors know what they are talking about as they are SemWeb developers themselves.
Although a little self advertisement and some missing languages, its a good thing to read. If you need info about RDF Query languages, read it.
My previous demand about "optional joins in queries" is answered by SeRQL."
The report is an excellent example of the current features required from a query language. From what I can tell iTQL implements 11 of the 14. Some of the others are fairly trival to add support for (like the data type support).