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Re: Making progress on graphs

From: Steve Harris <steve.harris@garlik.com>
Date: Wed, 16 May 2012 13:53:20 +0100
Cc: Richard Cyganiak <richard@cyganiak.de>, RDF Working Group WG <public-rdf-wg@w3.org>
Message-Id: <7FC036BB-0DB7-4751-B419-19BF4C6FECD2@garlik.com>
To: Ivan Herman <ivan@w3.org>
On 2012-05-14, at 05:37, Ivan Herman wrote:
> 
> On May 13, 2012, at 22:54 , 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”).
> 
> You are right that these particular issues seem to have general consensus. My concern is that, by taking a formal resolution on this now, we get ourselves into a false sense of security of having solved the named graph issue. And that is not the case or at least there is no consensus that being the case. Hence my reluctance of taking your proposal as a formal step.

But, I would have thought that /some/ step is a good idea.

> For example, Sandro also formally speaks of quads: these are widely used, never defined, and obviously closely related to the issue of named graphs. This is not part of your proposal.

Widely, but not universally - the source of some of the vagaries in the SPARQL spec is that there are quads-based systems, and collections-of-graphs based systems (and some do both). One example is the existence of empty graphs - those are meaningless in quads-based systems, but entirely sensible in collections-of-graphs.

- Steve

> I do not think that Sandro's document is 'highly controversial'; it is a much less radical approach than many that was discussed in the past few months. In this in this sense that it is a good basis of discussion (in my view).
> 
> Ivan
> 
> 
> 
>> 
>> 
>> So far I have heard no objections to this.
>> 
>> 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
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>> 
>> 
> 
> 
> ----
> 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
> 
> 
> 
> 
> 
> 

-- 
Steve Harris, CTO
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Received on Wednesday, 16 May 2012 12:53:54 GMT

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