[Tracker] Keywords from pdf dokuments

[Joerg Beyer <j beyer web de>]

Hello,

I have Tracker 0.8.17 on ubuntu running - everything is fine. But I
can't find keywords from pdf documents in the index. Pdf keywords are
something like tags. When I index a pdf like this:

/usr/lib/tracker/tracker-extract -v 3 -f example.pdf

then I see this among the verbose output:
...
     nao:hasTag [ a nao:Tag ;
     nao:prefLabel "myFirstTag"] ;
     nao:hasTag [ a nao:Tag ;
     nao:prefLabel "mySecondTag"] ;
...

This looks fine - but the keywords seem not to be in the index. This here

tracker-info example.pdf | grep myFirstTag

has no outout.

Is there a way to search for pdf documents by their keywords?

    thanks in advance
    Joerg