Re: [Tracker] Tracker and Semantic links

[Jamie McCracken <jamiemcc blueyonder co uk>]

scaroo wrote:
> Hi jamie and kudos for your greqt work.
> I am a satisfied user of Tracker particularly with the Deskbar Handler !
> I d like to know if you plane to allow the user (or dev) to be able to
> define links between first class object type. Well that s not clear,
> shame on my poor English, so here is an example :
> we have a picture and a people, they can be linked by many different
> ways : "is_authored_by",  "represents", "adviced_by", "taken_by",
> "gimped_by" and so on...
>
> Instead of creating tags representing those links, why not describe
> them formally and then using them as a bridge between two or more
> objects ? The user could define new kind of links. For example, a
> photographer could define a "buyed_by" link and so could find any
> customer having bought a particular picture. More interestingly, the
> links being bi-directional, he could find all the pictures bought by
> one client.


We already have generic support for this in the DB but I have not 
exposed a Dbus API for it yet. The link types would include things like 
a playlist item to link a file to a playlist, an attachment item to link 
a file attachement to an email etc - its totally generic and open ended 
so it could be used for any type of linking.

Exposing this powerful linking will be done in future versions.



> And you know what ? A XML dialect exists just for that : OWL
> For example, to define the link "is_located_in", linking a city and a
> country can be described like this :
>
> <!-- définition of classes "city" et "Country" -->
> <owl:Class rdf:ID="City" />
> <owl:Class rdf:ID="Country" />
>
> <!-- définition of the propertie « is_located_in » -->
> <owl:ObjectProperty rdf:ID="isLocatedIn">
>  <rdfs:domain rdf:resource="#City" />
>  <rdfs:range rdf:resource="#Country" />
> </owl:ObjectProperty>
>
> <!-- création of "France" -->
> <Country rdf:ID="France">
>  <name>France</name>
> </Country>
>
> <!-- création of "Paris", located in France -->
> <City rdf:ID="Paris">
>  <name>Paris</name>
>  <isLocatedIn rdf:resource="#France" />
> </City>

yes I hope to avoid that as a nice clean dbus api should do the job 
without needing to know OWL

> Another remark, on the freedesktop project page, it is stated that you
> will support Contact as a first class object type. Why not extends
> this concept to People, of who i can optionally have some contact
> informations ?

It will do - Contact is just another name for friend/people

> For example, if I want to query tracker for the sound compositor of a
> movie I have on my disk, I d like to know which other movies I own he
> worked on, his age, etc... Of course, that suppose that tracker has
> this information, maybe from the ogg/thera tags or something, but the
> point is that I do not know this people, I do not have any contact
> data about him/her, but I d like to know more about him.

To do that one would have to link the data (a contact object to a file 
object and then define the relationship) The composer or a piece of 
music is just  string metadata to tracker so its up to the user to make 
the connections.

> Maybe all of this is out of the scope of Tracker, but that would be a
> big step to the buzzworded Semantic Desktop.

It certainly has that capability but whether it will be exploited is 
another matter. Tracker aims to do the simple things well (like tagging) 
but also provide more complex linking - it remains to be seen how usable 
the linking will be compared to tagging.

Thanks for your input.

--
Mr Jamie McCracken
http://jamiemcc.livejournal.com/