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dataset semantics -- was Re: ACTION-278: grammar for TriG

From: Sandro Hawke <sandro@w3.org>
Date: Sun, 07 Jul 2013 07:34:57 -0400
Message-ID: <51D95261.1090504@w3.org>
To: public-rdf-wg@w3.org
On 07/07/2013 06:24 AM, Markus Lanthaler wrote:
> On Sunday, July 07, 2013 12:50 AM, Eric Prud'hommeaux wrote:
>> We can be conservative or liberal about what can go the the graph name
>> position:
>>
>> [...]
>>
>> I prefer the latter as it encourages the good practice of making
>> assertions about labeled graphs, e.g.
>> [[
>>    [ :utteredBy "Bob" ] { <moon> <madeOf> <greenCheese> }
>> ]]
> Me too but under the current semantics those wouldn't be assertions about
> the labeled graph as the graph name doesn't denote the graph. I still find
> that very problematic.
>
>

It's not that the name doesn't denote the graph, it's that it doesn't 
*necessarily* denote the graph.  Eric's example will work fine in a 
context where suitable dataset semantics are in use. Earlier, I gave the 
example that this could be flagged by having the triple { <> a 
rdf:BoundDataset } in the default graph. Another name for that might be 
"Direct".

In contrast, we might also have a WebCacheDataset, or WebViewDataset, or 
GraphStoreSnapshot, in which the graph names denote g-boxes whose 
contents are the associated graphs. (Change-over-time here is a problem, 
but it's the same problem we have throughout the RDF world.)

Now that we have blank node graph names available, I'm thinking the most 
popular dataset semantics will be a combination: for URLs, the 
graph-name denotes the g-box; for blank nodes, the graph-name denotes 
the graph.   I'm not sure which way to treat genids - it depends if we 
want the genid-creator to be obligated/encouraged to publish the graph 
at the genid URL.

But this is too speculative to put into a document that's slated to 
become a REC by the end of the year.  So instead, dataset semantics are 
an extensibility point, and we can experiment for a while.

       -- Sandro
Received on Sunday, 7 July 2013 11:35:06 UTC

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