It looks like the W3C has promoted SPARQL to that of a standard. The SPARQL Protocol and RDF Query Language is another "SQL on steroids" that allows you to query RDF documents.
This news is the latest in what seems to be a growing trend to extend or enhance SQL to work against non-relational databases. There is a long history of success in embedding or calling SQL from business software applications as an effective means of accessing data. Using the same pattern with an enhanced SQL for non-relational data seems to be very promising. There are competing patterns that are also emerging where the SQL is generated under the covers and not by the application developer at all. I have blogged on this in a larger article documenting trends in data access strategies for software developers.