Re: Semantics (was: Re: desktop-devel-list Digest, Vol 50, Issue 26)

[Anders Feder <lists anders feder dk>]

A little note on the topic:
I've summarized the stack we're approaching between my talks with
Sebastian and the discussion here, at:
http://live.gnome.org/RDFStack

man, 23 06 2008 kl. 21:01 +0200, skrev Anders Feder:
> Sorry Michael, must have missed your e-mail among the digests last week.
> 
> tor, 19 06 2008 kl. 12:14 +1000, skrev Michael Gratton:
> > Ahh, right. Can something be constructed to translate SPARQL (or some
> > useful subset) into Tracker's query format?
> 
> A subset, yes, but as Wouter points out Tracker is XESAM-based which
> 'only' cover simple query cases, so certain advanced SPARQL queries (in
> particular 'join'-like operations) would map rather poorly into XESAM.
> 
> How such queries would be handled by a translator is undefined. In
> theory, one could do something like constructing the actual graph
> resulting from i.e. a join operation in memory, but that is really quite
> a hack that doesn't scale well for big data sets.
> 
> I've communicated with both Tracker and XESAM maintainers and they
> appear quite skeptical about RDF/SPARQL support in the short- to
> mid-term.
> 
> I would suggest that we hack together an interim adapter for XESAM as a
> proof-of-concept. Once that works, it should be easier to persuade
> everyone to reconsider native RDF support.
> 
> > Do you know how applications typically use those interfaces? The W3C
> > case study states that users can tag files in Dolphin. When a user does
> > so, does Dolphin save the tag as well as pushing it to Soprano, or just
> > the latter? I assume it doesn't save a copy, but that means when
> > displaying files, it needs to query Soprano for every one? If the
> > performance doesn't suck, this might be a reasonable model, but you'd
> > want to ensure Soprano is always well behaved. :)
> 
> I believe Dolphin pushes the tag triple into Soprano, yes. This should
> be quite like a social networking site storing tags in a relational
> database.
> 
> However, I imagine the other model could also be supported: Dolphin
> stores tags in a store of its own and this store is exposed as a Soprano
> backend. Dolphin can access its own store directly, but other
> applications will go through the SPARQL layer.
> 
> Currently, this would be done with Sopranos backend classes. In our
> case, this would be where the D-Bus interface you suggested would come
> into the picture and I'm almost certain Sebastian would be happy to
> support such an interface in Soprano as well.
> 
> > I dunno, maybe having a common service is the way to go, but something
> > will need to be done to make it easy for developers to implement.
> 
> Yes, I agree. Something like a library that makes it trivial to
> implement the RDF backend D-Bus interface should be available.
> 
> -- 
> Anders Feder <lists anders feder dk>
> 
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-- 
Anders Feder <lists anders feder dk>