[Xesam] Meaning of xesam:url

[Sebastian Trüg]

On Monday 04 August 2008 20:46:40 Mikkel Kamstrup Erlandsen wrote:
> 2008/8/3 Michael Albinus <michael.albinus at gmx.de>:
> > Hi,
> >
> > I'm currently playing with different search engine. It looks to me like
> > all of them have an own idea of xesam:url, which makes it a little bit
> > hard to interpret in a client.
> >
> > - The XesamOntology95 says as data type "list of URLs". This seems to be
> >  an error, all engines return just a string.
>
> Yes, this should just be a string. Luckily no-one used it like this :-)
>
> > - When it is a local file, beagle returns a "file:///a/b" URL. Contrary,
> >  strigi returns a local file name like "/a/b". I guess, it shall always
> >  be a URL.
>
> Right.
>
> > - The engines use xesam:url for providing further information. Examples:
> >
> >  * "file:///.../Mail/Local Folders/Inbox/?id=240915" means file "Inbox",
> >    char position 240915 (beagle)
> >
> >  * "/home/albinus/Mail/default/21/ChangeLog" means (email in) file
> >    "21", attachment "ChangeLog" (strigi)
> >
> >  * ".../gnome-keyring_2.20.orig.tar.gz/gnome-keyring-2.20/po/ChangeLog"
> >    means a file in a zipped tar (strigi)
> >
> >  I believe, such information shall be given in other xesam fields.
>
> Well, that's hard to decide. Requests for standardizing the contents
> of xesam:url has been aired a few times, but I think it is really hard
> to achieve. For example Evolution and KMail handles email uris very
> differently, same applies for all manner of similar apps between KDE
> and Gnome. It would almost be a whole spec in itself to do full
> standadization of this.
>
> I think you can only trust it when you have good reason to do so. Fx
> for files, web pages, and the likes. If you have apriori knowledge of
> your platform you can use them as well. For instance Gnome's deskbar
> can open the emails in Evolution.
>
> I wish we could do better, but I don't have many ideas. Anyone with a
> fresh mind please chime in.

In Nepomuk I use an identifier string value which can be set to anything that 
allows the application to identify the email or whatever. xesam:url is only 
used for files, actually to store their path (like strigi does) but here I 
agree that a URL would be better.
So for emails for example I would say: no xesam:url at all. That should only 
be used for files (local or remote).

Cheers,
Sebastian