Re: graph names denoting the graph (suggested change to Concepts)

On 06/06/2013 01:14 AM, Andy Seaborne wrote:
> On 05/06/13 18:56, Sandro Hawke wrote:
>
>>  I'm worried
>> about how Alice can send Bob a dataset in which the graph names denote
>> their graph (and in which she is asserting the triples in the default
>> graph).   How can Alice communicate this intent to Bob?    Doing it
>> out-of-band is of course possible (she calls him on the phone), but
>> that's very messy.   Can she do it in-band, such as by adding a magic
>> triple to the default graph?     Unless that's licensed by the RDF
>> Recommendations, I don't think so.   If the RDF Recommendations say all
>> the triples/quads in a dataset are meaningless (as they currently do),
>> then Bob isn't licensed to consider them as conveying Alice's intent.
>
> There's nothing to stop additional information being given - you can 
> additionally describe the dataset and it's usage of graph labels.
>
> What is needed is that vocabulary definition - it does not even have 
> to be rdf:*
>
> When receiving any document, the receiver has to assess what of it 
> they are going to interpret/trust. (The real question is whether to 
> trust the publisher has followed RDF specs - we can't do anything 
> about that.)
>
> Sandro - what text in the docs do you think blocks that?
>
> Are you asking that the default graph is interpreted as it would if it 
> were a single graph at that location?
>

Yes, I think that would do it.     If 4.2 were normative, it would 
provide this functionality in a roundabout way.   It says:

//

      If an RDF dataset
    <https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#dfn-rdf-dataset>
    is returned and the consumer is expecting an RDF graph
    <https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#dfn-rdf-graph>,
    the consumer is expected to use the RDF dataset's
    <https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#dfn-rdf-dataset>
    default graph.

So, that way a client is licensed to take the default graph as being 
asserted, essentially if it wants to (by deciding it was expecting an 
RDF graph).

I guess the straightforward way to address this would be to express it 
as minimal (baseline) dataset semantics: the RDF Semantics for a dataset 
is the RDF Semantics of its default graph.    Then the default graph can 
tell people what other, additional semantic conditions might apply (like 
that it's a bound dataset, or whatever).    Also,  then section 4.2 
becomes properly non-normative (it would just be expressing a logical 
consequence) instead of carrying important information as it does now.

cf 2013/02/06-rdf-wg RESOLVED:  Add a non-normative statement to RDF 
Concepts explaining that if a RDF serialization format supports 
expressing both datasets and graphs, that a consumer should use the 
default graph if it is expecting a graph.   (Actual wording to be 
handled by editor)

There's a sort of theoretical argument against this, that people are 
currently publishing SPARQL and TriG and N-Quads without having this 
meaning in mind, but I can't think of how changing this could actually 
cause any problems for any of these people.    I think it would only 
cause a problem for people who would have a problem with that resolution 
and section 4.2 -- people who are somehow using the default graph to  
contain triples they don't want other systems to use.

       -- Sandro




>     Andy
>
>>
>>         -- Sandro
>>
>>
>>
>
>
>