Re: [Tracker] Using tracker extractors from other applications

[Philip Van Hoof <spam pvanhoof be>]

On Sat, 2010-11-20 at 09:27 -0500, Nikolaus Rath wrote:
> Ivan Frade <ivan frade-Re5JQEeQqe8AvxtiuMwx3w public gmane org> writes:

Hi Nikolaus Rath,


> Well, I would be quite happy to submit patches.

Good!

> But at the moment I still have absolutely no idea what GetMetadata()
> returns. What is a "turtle format"? What is a "subject"? What defines
> a node? I think you are assuming that I know something which I
> actually don't..

Yes, we kinda assume that people who want to contribute read the Turtle,
SPARQL and SPARQL Update specifications alongside the Nepomuk ontology.

Turtle is a format to express triples in. It's reused by SPARQL, our
query language.

> Btw, if tracker itself does not use ExtractorHelper, how does e.g.
> tracker-miner make sense of the metadata?

The tracker-miner combines the sets of triples coming from tracker-
extract in the Turtle format to form a SPARQL Update and that query it
feeds to tracker-store.

> Maybe I could use that code as a start instead. I tried to follow the
> invocation of get_metadata_fast_async but could not really identify
> the part where the metadata is parsed.

The metadata coming from tracker-extract isn't further parsed, that
would be silly, it's used to generate a SPARQL Update query. It can do
this because SPARQL Update uses Turtle as format.

You would have found all this yourself if you would have looked up
SPARQL Update and Turtle in Google and read the specifications. Which I
recommend you doing before anything else.


Cheers,

Philip

-- 


Philip Van Hoof
freelance software developer
Codeminded BVBA - http://codeminded.be