Re: Agenda Topic / Issue: Clarify the meaning of "ignore" with respect to attributes that have no legal value

Tore Eriksson wrote:
> Mark Birbeck <mark.birbeck@webbackplane.com> wrote:
>> The final piece of the jigsaw is to bring back in the earlier point,
>> i.e., that the spec allows us to create a triple from 'foobar'
>> provided that we don't put it into the default graph. In this case my
>> parser might place the 'unknown' triple into a separate graph:
>>
>>   Default graph:
>>     _:a foaf:name "Mark" .
>>
>>   Graph A:
>>     <#shane> ex:blah _:a .
>>
>> Now, as you can see, even though it's in a separate graph, I could
>> still run a SPARQL query over *both* graphs to yield the following
>> triples:
>>
>>   <#shane> ex:blah _:a .
>>   _:a foaf:name "Mark" .
>>
>> And since the parsing algorithm caused us to generate a bnode despite
>> not understanding 'ex:blah', then the triples in the two separate
>> graphs are 'aligned'.
> 
> My understanding from reading "Named Graphs, Provenance and Trust" [1],
> is that blank nodes can't be shared between graphs, making this type of
> query impossible. Graph A has to be a superset of the default graph for
> this to work.
> 

Unfortunately, at least at the moment, there is no formal specification
for named graphs. Alas!, [1] does not constitute an authoritative
reference for a standard (although it may very well be the way to do it
technically!). Note that the SPARQL document does not make such strong
statements, so strictly referring to SPARQL Mark is probably right. But,
at the moment, this is a grey area:-(

Ivan


> [1] http://www2005.org/cdrom/docs/p613.pdf
> 
> Regards,
> 
> Tore Eriksson
> 
> _______________________________________________________________
> <> dc:creator [
>    foaf:name "Tore Eriksson",
>              "トーレ エリクソン"@jp;
>    foaf:mbox_sha1sum "2bd9291b301f112775e118f96eb63314594b1a86";
>    foaf:workplaceHomepage <http://www.taisho.co.jp/> ].
> 
> 
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
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