Reported on the mailinglist by Drew Perttula:
I want to sort results by the presence of a class:
I stumbled on VALUES, but I welcome other suggestions for how to accomplish my query. Meanwhile, this query seems to reveal a bug in VALUES.
Without the VALUES block in there, I get rows with ?comp and ?label, and of course ?isServiceComponent is always undef. All rows are returned. This seems correct.
With the query as written above, a few things go wrong at once: all ?label results become undefined, and rows with no ?isServiceComponent are omitted, like this:
It's kind of like the rdfs:label constraint and the OPTIONAL keyword both got ignored, turning the '?comp a :ServiceComponent' pattern from optional to required and turning the VALUES into something that's always applied.