Re: [Tracker] Result of GetMetadata DBUS Method

[Nikolaus Rath <Nikolaus rath org>]

Adrien Bustany <abustany-rDKQcyrBJuzYtjvyW6yDsg public gmane org> writes:
> Le Sat, 24 Sep 2011 18:50:06 -0400,
> Nikolaus Rath <Nikolaus-BTH8mxji4b0 public gmane org> a Ãcrit :
>
> > Adrien Bustany <abustany-rDKQcyrBJuzYtjvyW6yDsg-XMD5yJDbdMReXY1tMh2IBg public gmane org>
> > writes:
> > > > > > In tracker 0.8.17, an example result of the GetMetadata DBUS
> > > > > > method is
> > > > > >
> > > > > > Âa nfo:PaginatedTextDocument ;
> > > > > > Â Â Â Â nie:title "SV Meldung" ;
> > > > > > Â Â Â Â nco:creator [ a nco:Contact ;
> > > > > > Â Â Â Â nco:fullname "nikratio"] ;
> > > > > > Â Â Â Â nie:contentCreated "2011-08-10T20:12:38Z" ;
> > > > > > Â Â Â Â nao:hasTag [ a nao:Tag ;
> > > > > > Â Â Â Â nao:prefLabel "()"] ;
> > > > > > Â Â Â Â dc:format "application/pdf" ;
> > > > > > Â Â Â Â nie:description "()" ;
> > > > > > Â Â Â Â nfo:pageCount 1 ;
> > > > > > Â Â Â Â nie:plainTextContent "blablabla" .
> > > > > >
> > > > > > With tracker 0.10.21, however, the same document now gives
> > > > > >
> > > > > > Âa nfo:PaginatedTextDocument ;
> > > > > > Â Â Â Â nie:title "SV Meldung" ;
> > > > > > Â Â Â Â nco:creator [ a nco:Contact ;
> > > > > > Â Â Â Â nco:fullname "nikratio"] ;
> > > > > > Â Â Â Â nie:contentCreated "2011-08-10T20:12:38Z" ;
> > > > > > Â Â Â Â dc:format "application/pdf" ;
> > > > > > Â Â Â Â nie:description "()" ;
> > > > > > Â Â Â Â nao:hasTag ?tag1 ;
> > > > > > Â Â Â Â nfo:pageCount 1 ;
> > > > > > Â Â Â Â nie:plainTextContent "blablabla" .
> > > > > > } } WHERE { {
> > > > > > ?tag1 a nao:Tag ; nao:prefLabel "()" .
> > > > > >
> > > > > >
> > > > > > I don't know enough about the syntax used here, so I won't claim
> > > > > > that it's wrong. However, rdflib fails to parse this and thus
> > > > > > breaks my application.
> > > > > >
> > > > > > Can someone tell me if this is a bug in tracker or in rdflib?
> > > > >
> > > > > Could you share the error message that rdflib gives you?
> > > >
> > > > Sure, it's at http://code.google.com/p/rdflib/issues/detail?id=190
> > >
> > > Most likely rdflib doesn't like the fact that the WHERE of the
> > > INSERT is not closed?
> >
> > rdflib actually tries to parse this as Turtle RDF. But unless I'm
> > reading the specs wrong, Turtle does not have a WHERE, so am I right
> > to assume that GetMetadata has been changed to no longer return valid
> > Turtle RDF, but partial SPARQL statements?
> >
> > If so, this makes it very hard to use GetMetadata() for anything else
> > but tracker. Is there any way to get something that's easier to parse
> > from tracker-extract?
>
> Well, tracker-extract actually *never* returned turtle, at least as far
> as I know (now, I'm not completely familiar with that component). I
> guess the fact that previous versions returned SPARQL that looked like
> turtle is at most a coincidence :) (note: turtle does not have INSERT
> either).

Well, extract-metadata does not return an INSERT. Until the WHERE
started to appear, it was always valid turtle.

> GetMetadata being an internal API call, it's not exactly
> meant to be easy to use for 3rd party apps, and it's actually tied
> quite tightly with the SPARQL the the FS miner generates. I'm not sure
> of what would be the easiest way for you to use that API now :/ Getting
> the complete SPARQL and inserting it into an in-memory db (for example
> Sesame) before querying it would be an option, but that really sounds
> complex and sub-optimal... A simpler option would be to apply a few
> transformations to the SPARQL to make it look like turtle again, but
> that does not sounds like a bullet proof solution.

Would it maybe be possible to add an additional API call, say
ExtractPlaintext that returns just the (unstructured) plain text and
could easily be used by 3rd party apps?


Best,

   -Nikolaus

-- 
 ÂTime flies like an arrow, fruit flies like a Banana.Â

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