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

On 06/06/13 16:33, Sandro Hawke wrote:
> 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?
>>

But is there any current text that blocks that?  I don't see any.

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

4.2 is specifically about content negotiation.  It says that "if 
expecting an RDF graph" so it does not really say anything about the 
treatment of default graph when in the dataset.

A client application gets some data; there is a statement that dataset 
uses denotational labelling; the app can trust that or not, same as 
trusting the publisher on any other statement, like the date the 
dataset/graph/HTML doc was written.


>   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:

If we re-open up the semantics of datasets discussion, why would this be 
the one semantic we have?  For better or worse, we have a WG position.

> 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.

I have trouble seeing why anyone would publish triples that don't want 
anyone else to use.

	Andy

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

Received on Friday, 7 June 2013 09:18:20 UTC