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Re: RDF-ISSUE-140 (dataset-comparison): RDF Dataset Comparison (Ivan Herman) [RDF Concepts]

From: Andy Seaborne <andy@apache.org>
Date: Fri, 09 Aug 2013 17:33:08 +0100
Message-ID: <520519C4.3030508@apache.org>
To: public-rdf-wg@w3.org
On 09/08/13 15:53, Markus Lanthaler wrote:
> On Friday, August 09, 2013 4:17 PM, Ivan Herman wrote:
>> On Aug 9, 2013, at 11:43 , Markus Lanthaler <markus.lanthaler@gmx.net>
> wrote:
>>> On Friday, August 09, 2013 11:24 AM, Ivan Herman wrote:
>>>> We had a long discussion some times ago and we concluded that graphs in
>>>> a dataset share bnodes. As a consequence, I believe Gavin's statement
>>>> seems to be the proper conclusion...
>>>
>>> Yes, the graphs share bnodes but I'm not sure how that relates to the
> graph
>>> names. So you could as well argue that there are two sets of blank node
>>> identifiers and that in the examples below the mappings are
>>>
>>> Example 1: _:y -> _:x (nodes) | _:y -> _:x (graphs)
>>> Example 2: _:y -> _:y (nodes) | _:y -> _:x (graphs)
>>>
>>> Or do I miss something? As far as I understand it, there's no
> relationship
>>> between a blank node identifier used as graph name and a blank node
>>> identifier used as node (you could say they are in different scopes) from
>>> which I conclude that the same bnode id mappings can be mapped
> differently.
>>>
>>
>> Yes, we could do that. But that seems to be confusing, at least to me.
>
> Yes, it's confusing. But I think it is a consequence of the decision to not
> define any dataset semantics. Blank nodes used as graph names do not denote
> the graph.

I don't see that matters - this is whether one dataset is isomorphic to 
another.  It is a structural relationship and not about denotation.

	Andy

>
>
>> Is there a use case for the separation of the different scopes?
>
> Well, ask the people who voted against letting bnodes denote the graph.
>
>
>> It
>> looks way more obvious to me to consider a bnode as a label and a bnode
>> in one of the graphs as being identical...
>
> Fully agreed, but I think under the current semantics they are not. Actually
> the same is true for IRIs but since their scope is global the difference
> doesn't matter.
>
>
> --
> Markus Lanthaler
> @markuslanthaler
>
>
Received on Friday, 9 August 2013 16:33:36 UTC

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