Re: [Tracker] Basic Reasoning

[Martyn Russell <martyn lanedo com>]

On 13/06/13 01:13, Ivan Frade wrote:
> Hi,

Hi,

> To be more precise, Tracker can solve queries much more complicated than
> those... but you need to be specific on the properties.
>
> For example "Give me the title property of all instances of class Music,
> that have an artist [property linking to an artist instance] with name
> "Metallica".

Indeed, if you want to see an example of this, from the console, run 
tracker-needle:


  $ export TRACKER_VERBOSITY=3
  $ export G_MESSAGES_DEBUG=all
  $ tracker-needle

  ...

You will see queries like this for music (which can be reasonably complex):

"""
SELECT ?urn nie:url(?urn) tracker:coalesce(nie:title(?urn), 
nfo:fileName(?urn)) fn:string-join((?performer, ?album), " - ") 
nfo:duration(?urn) nie:url(?urn) WHERE {
                  {
                    ?urn nmm:musicAlbum ?match
                  } UNION {
                    ?urn nmm:performer ?match
                  } UNION {
                    ?urn a nfo:Audio .
                    ?match a nfo:Audio
                    FILTER (?urn = ?match)
                  }
                  {
                    ?match fts:match "love"
                  } UNION {
                    ?match nao:hasTag ?tag .
                   FILTER (fn:contains (fn:lower-case 
(nao:prefLabel(?tag)), "love"))
                  } .
                    ?urn nmm:performer [ nmm:artistName ?performer ] ;
                       nmm:musicAlbum [ nie:title ?album ] ;
                       nie:url ?tooltip .
} ORDER BY DESC(nfo:fileLastModified(?urn)) ASC(nie:title(?urn)) OFFSET 
0 LIMIT 500
"""

--
Regards,
Martyn

Founder and CEO of Lanedo GmbH.