There were some folks looking into building RDFPath, an XPath-like syntax for referring to RDF data, although it hasn't had any updates for over a year. The syntax is fairly general purpose though.
For the RPath language I'm using in the SWC, I probably have different goals, since the expressions are intended to be used in UI elements, like XPath expressions are used in XForms. As such, they don't connect to a giant database of info.
For example, I might use:
director[birthdate/year < 1950]
which in RPath would return all nodes of directors born before 1950, but that wouldn't make sense to use on a client, as a client wouldn't have a database of directors to scan through unless it sent the query off to some remote server.
But, given two RDF files sent to the client each describing a different movie, one could pick out cast members that starred in both using:
children(<movie1id>/cast) & children(<movie2id>/cast)
Thus, there needs to be a balance between making the expressions powerful, yet ensuring that they make sense and performance doesn't suffer as a result.
Hmmm. I seem to have gotten myself into a situation where I have to do some real paid-for work for a few weeks. So I might not get as much time to work on the SWC.
The only thing I've done lately is change the history panel to use labels instead of URIs, and started creating a dialog box for adding custom datasources.
I wonder how I am
doing all this.