Re: Making progress on graphs

On Wed, May 16, 2012 at 7:30 AM, Sandro Hawke <sandro@w3.org> wrote:

> On Wed, 2012-05-16 at 13:20 +0200, Guus Schreiber wrote:
> > On 14-05-2012 08:03, Pat Hayes wrote:
> > >
> > > On May 13, 2012, at 3:54 PM, Richard Cyganiak wrote:
> > >
> > >> Hi Ivan,
> > >>
> > >> On 13 May 2012, at 16:15, Ivan Herman wrote:
> > >>> it looks to me that Sandro's draft document:
> > >>>
> > >>>
> https://dvcs.w3.org/hg/rdf/raw-file/d96c16480e42/rdf-spaces/index.html
> > >>>
> > >>> would be a good way to 'settle' things (see [1]), too.
> > >>
> > >> Sandro's draft takes explicit position on a *all* issues, many of
> which are highly controversial. By bundling non-controversial and
> controversial issues all into one big package, this blocks progress on the
> sub-issues where we actually seem to all agree. So I repeat:
> > >>
> > >>
> > >> PROPOSAL: The abstract syntax for working with multiple graphs in RDF
> consists of a default graph and zero or more pairs of IRI and graph. This
> resolves ISSUE-5 (“no”), ISSUE-22 (“yes”), ISSUE-28 (“no”), ISSUE-29
> (“yes”), ISSUE-30 (“they are isomorphic”), ISSUE-33 (“no”).
> > >>
> > >>
> > >> So far I have heard no objections to this.
> > >
> > > +1 to all of this. FWIW, I have been operating under these assumptions
> for at least the last two months.
> >
> > I've added the proposal from Richard to the agenda.  As a minimum we
> > should have straw polls on all the them, as proposed by Sandro early on
> > in this thread. Resolving them appears more controversial, although this
> > last remark from Pat is an important "data point" for me.
>
> And, for the few lazy people who haven't read every message in this
> thread  :-)   I'm formally objecting to that proposal as written.   I
> read it as saying that quadstores and quad syntaxes would not be capable
> of storing this abstract syntax.  But I think quads are a very useful
> and widely used model, and it would be a serious mistake to exclude
> them.  Richard doesn't seem to think he is excluding them, so there may
> be a solution that just involves wording tweaks, but I can't see it
> right now, and Richard sent his regrets for today.
>

Just for the record -- quad stores are perfectly capable of storing
datasets with empty graphs without losing the existence of those graphs.
Nothing says that the internal data structures used by the quad store have
to exactly match the structure of the dataset. All that matters is that the
store is capable of reproducing the dataset when queried, exported, etc.

For instance, Mulgara (a quad store) uses an internal system graph to track
the existence of all graphs that it stores. For an empty graph, there will
simply be a quad recording the existence of that graph IRI in the system
graph, and an absence of quads using that graph IRI in the fourth column.

-Alex



>
>    -- Sandro
>
> > Guus
> >
> > >
> > > Pat
> > >
> > >>
> > >> Best,
> > >> Richard
> > >>
> > >>
> > >>
> > >>> At the moment it seems to collect all the various issues that we
> have discussed with a fairly clear way of moving forward.
> > >>>
> > >>> Ivan
> > >>>
> > >>>
> > >>> [1]
> http://lists.w3.org/Archives/Public/public-rdf-wg/2012May/0178.html
> > >>>
> > >>>
> > >>> On May 13, 2012, at 16:59 , Richard Cyganiak wrote:
> > >>>
> > >>>> All,
> > >>>>
> > >>>> We've been talking our way up and down the design space for
> multigraphs for a year now, with not much to show for it. We still have not
> settled on a basic design.
> > >>>>
> > >>>> Once we do settle on a basic design, the real work only starts
> since we need to nail down the details. This will take time. Our charter
> says that all documents should go to LC *this month*, and obviously we are
> nowhere near ready for this.
> > >>>>
> > >>>> So I think it's time to stop exploring the design space, and start
> collapsing it by making decisions.
> > >>>>
> > >>>> Obviously there is still strong disagreement on many things when it
> comes to multigraphs, but it seems to me that all proposals on the table
> accept a basic *abstract syntax* that is quite similar to the RDF datasets
> in SPARQL, and even the most adventurous experiments don't really stray
> from that forumla. Therefore:
> > >>>>
> > >>>>
> > >>>> PROPOSAL: The abstract syntax for working with multiple graphs in
> RDF consists of a default graph and zero or more pairs of IRI and graph.
> This resolves ISSUE-5 (“no”), ISSUE-22 (“yes”), ISSUE-28 (“no”), ISSUE-29
> (“yes”), ISSUE-30 (“they are isomorphic”), ISSUE-33 (“no”).
> > >>>>
> > >>>>
> > >>>> RATIONALE: All proposals on the table are based on an abstract
> syntax very similar to SPARQL's notion of an RDF dataset, although there is
> no consensus on the semantics and the terminology. Making a decision on the
> basic abstract syntax would unblock the work, and allow various strands of
> required detail work to proceed independently, hopefully leading to
> additional resolutions to remaining questions, such as:
> > >>>>
> > >>>> • What's the formal semantics of the abstract syntax?
> > >>>> • Definition of the concrete syntaxes (N-Quads, etc.)
> > >>>> • Describing how to work with this in the Primer
> > >>>> • What do call the pairs? “Named graphs” or something else?
> > >>>> • What to call the entire thing? “RDF dataset” or something else?
> > >>>> • Can blank nodes be shared among graphs?
> > >>>> • What additional terminology (rdf:Graph etc) needs to be defined?
> > >>>>
> > >>>> Best,
> > >>>> Richard
> > >>>
> > >>>
> > >>> ----
> > >>> Ivan Herman, W3C Semantic Web Activity Lead
> > >>> Home: http://www.w3.org/People/Ivan/
> > >>> mobile: +31-641044153
> > >>> FOAF: http://www.ivan-herman.net/foaf.rdf
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >>
> > >>
> > >>
> > >
> > > ------------------------------------------------------------
> > > IHMC                                     (850)434 8903 or (650)494
> 3973
> > > 40 South Alcaniz St.           (850)202 4416   office
> > > Pensacola                            (850)202 4440   fax
> > > FL 32502                              (850)291 0667   mobile
> > > phayesAT-SIGNihmc.us       http://www.ihmc.us/users/phayes
> > >
> > >
> > >
> > >
> > >
> > >
> >
> >
>
>
>
>