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Re: complete vs partial graph semantics

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Thu, 12 Apr 2012 12:49:43 +0100
Message-ID: <4F86C157.5060603@epimorphics.com>
To: public-rdf-wg@w3.org

>> The critical issue is what happens on the default case of no information.

Williams comments overtake this but anyway ...

> Put differently, as a test case:
>
> Trig Document 1 (D1):
>      <u>  {<a>  <b>  1 }
>
> Trig Document 2 (D2):
>      <u>  {<a>  <b>  2 }
>
> What is the merge/union of D1 and D2?
>
> OPTION 1:
>
>          It's a contradiction.  You can't merge D1 and D2.

Can't support.

(and there is a potential denial-of-service attack :-)

> OPTION 2:
>
>          Merge the graphs, producing Trig Document 3:
>
>          <u>  {<a>  <b>  1,2 }

+1

The current situation, or as close as we can determine it.

> OPTION 3:
>
>          It depends.  Use out-of-band information.   I argued against
>          this in my email to Arnaud yesterday, and seemed to convince
>          him.
>          http://lists.w3.org/Archives/Public/public-rdf-wg/2012Apr/0054.html
>
> OPTION 4:
>
>          It's not defined, when asked like this.  We use something
>          Trig-Like but different:
>
>            D1A<u>  {+<a>  <b>  1 }
>            D2A<u>  {+<a>  <b>  2 }
>          in which case the merge is:
>            D3A<u>  {+<a>  <b>  1,2 }
>
>          ==or==
>
>        D1B<u>  {=<a>  <b>  1 }
>        D2B<u>  {=<a>  <b>  2 }
>      in which case there is no merge; they are inconsistent.

OPTION 5:

{= ...} is complete
{...} is partial -- current situation is "partial"

As a general syntax comment though, it would be far better if the 
additional information were in triples, not in specialised syntax.  It 
means the facts can be passed onwards.

Where do they go?

The default graph is one possibility (but that might have other uses).

Another is a meta graph or manifest so a TriG file has a defailu graph, 
a meta graph and labelled graphs.  The meta graph has the relationship 
information.

{= ...} might be syntactic short-hand.


(I think one aspect of the difficulties around HR14 is that the 
information revealed by 200 vs 303 is not in the data.)

	Andy
Received on Thursday, 12 April 2012 11:50:20 UTC

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