Re: Attempt to provide semantics to Sandro's named graph design

On Apr 10, 2012, at 16:06 , Andy Seaborne wrote:

> Ivan,
> 
> Most of it makes sense to me.
> 
> Could you explain the need for conditions 3, please?  I see the need for a local functional mapping from <ui> to Gi, but why the reverse condition?
> 
> It seems at odds with web style of multiple names for things and also of merging data at the RDF level without inconsistencies arising.
> 
> If a process reads location "URL" at two different times T1 and T2, gets the same triples GV, which it labels events E1 and E2,
> 
> then the app can't write
> 
> E1 { GV }
> E2 { GV }
> 
> i.e. the use case for an archiving web crawler can't be addressed directly.
> 
> The cost of enforcing the condition when adding a new graph to an existing dataset is going to be not inconsiderable.

Hm. I think you are right. I am not sure what I had in mind when I added it to the conditions, but it is wrong. I have added a comment on the wiki page and will remove this later unless somebody feels it should be there. Thanks!

> 
> 
> "Subgraphs or Graphs"
> 
> I don't think this is a local syntax issue. The parts of the labelling may be in different datasets, which are then brought together (actually, not possible by condition 3)
> 

Yep, another reason to remove this.

But I am not absolutely sure what you are saying:-(

> Within one TriG file, several <u> {} blocks may make one graph labelled <u> overall -- that is a syntax issue.
> 
> ((I don't see why the merge of datasets isn't the merge of their graphs with the same URI + the (IRI, graph) pairs for non-overlapping IRIs.))
> 

Well, that may be doable... but this seems to be one (maybe the only real?) open issue at the moment in the WG.

Just thinking out loud: if (<u>,G) but <u> is _not_ of type rdf:Graph, ie, it is only labeling, then I could imagine a much more lax attitude in terms of subgraph vs. graphs. However, if <u> rdf:type rdf:Graph, ie, it is really a URI that denotes the graph, then the situation may be different...

Ivan




> 
> 	Andy
> 
> 
> 
> 
> On 10/04/12 14:42, Ivan Herman wrote:
>> Guys,
>> 
>> As a submission to tomorrow's discussion: I have tried to put some semantics 'meat' on the Sandro's skeleton design[1]. I have put it onto the wiki:
>> 
>> http://www.w3.org/2011/rdf-wg/wiki/Graphs_Design_6.1/Sem
>> 
>> it may provide a way to fold all this into the RDF Semantics with, I believe, a minimal amount of change to the current RDF Semantics (which is a plus for me!), pretty much as a separate section instead of rewriting the whole thing. It may also help in formulating some of the open issues.
>> 
>> I believe it reflects what Sandro thinks although I may of course be wrong...
>> 
>> Cheers
>> 
>> Ivan
>> 
>> [1] http://www.w3.org/2011/rdf-wg/wiki/Graphs_Design_6.1
>> 
>> 
>> ----
>> 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