Re: [Tracker] nfo:Image identifier

[Philip Van Hoof <spam pvanhoof be>]

On Tue, 2010-09-21 at 15:55 +0200, MichaÅ Frynas wrote:
> I have following problem. I'm developing a new ontology handling
> profile data. One of the attributes the profile contains is its icon.
> I'm trying to reuse some parts of existing Nepomuk ontologies, and
> that's why I'd like to utilize one of nfo:Icon or nfo:Image classes.
> I've written following description:

> mpo:hasIcon a rdf:Property ;
>     rdfs:label "hasIcon" ;
>     rdfs:comment "Reference to the icon assocciated with current
> profile" ;
>     nrl:maxCardinality 1 ;
>     rdfs:domain mpo:Profile ;
>     rdfs:range nfo:Image .
>
> After uploading my ontology, I import a ttl file having following
> dataset:
>
> <MyCar> a mpo:Profile ;
>         mpo:name "Car" ;
>         mpo:hasIcon "urn:uuid:981e3c86-b0be-e38c-f224-cc2dce8810c5" ;
>         mpo:xpos 10 ;
>         mpo:ypos 12 .

Because the rdfs:range of your mpo:hasIcon is a resource (nfo:Image) you
must use <urn> instead of "urn" like what your TTL snippet has atm.

You can also use [] for anonymous blank node. For example:

<MyCar> a mpo:Profile ;
        mpo:name "Car" ;
        mpo:hasIcon [ a nfo:Image ; nie:title 'Icon for Car'; etc ] ;
        mpo:xpos 10 ;
        mpo:ypos 12 .

But if you want to set <MyCar>'s icon to a resource that exists already
in the RDF store, for example because tracker-miner-fs has made a
resource for it (because it's a file), then you can do something like
this with a SPARQL INSERT query:

INSERT { <MyCar> a mpo:Profile ;
                 mpo:name "Car" ;
                 mpo:hasIcon ?icon ;
                 mpo:xpos 10 ;
                 mpo:ypos 12 . }
WHERE {
         ?icon nie:url 'file:///usr/share/pixmaps/caricon.png'
}


> where mpo:hasIcon is the Image Id i've received using that query:
> select ?s { ?s a nfo:Image .}

> And now, when I try to get my data using following query, I get
> nothing: select ?s ?t { ?s a mpo:Profile; mpo:hasIcon ?t . }
> Maybe someone knows what is wrong with it. 

Use <urn> instead of "urn", but you of course need to create the
nfo:Image first unless you use anonymous blank nodes as I explained
earlier.

> Is that ID urn:uuid:981e3c86-b0be-e38c-f224-cc2dce8810c5 a correct ID
> of nfo:Image?

We can't know, your sample isn't complete. But it looks like the subject
created for an anonymous blank node. For example a file on the FS.

Cheers,

Philip

-- 


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