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Re: RDF* semantics

From: Andy Seaborne <andy@apache.org>
Date: Fri, 9 Aug 2019 14:31:42 +0100
To: public-rdf-star@w3.org
Message-ID: <1eed9819-32da-7335-b4d3-f4114c94fe16@apache.org>
Reification can do 3 things: (close by are cases for named graphs)

1/ Talk about another triple in the graph - this is edge properties and 
is RDF* PG mode.

2/ Talk about something that isn't asserted or isn't known.
RDF* SA mode is close to this, I think.

:moon :color "Green".

   is not in the graph and

<<:moon :color "Green">> :saidBy :Bob .

   is in the graph.

or
<<:moon :color "Green">> :claimedFalse :Alice .

Having both modes does not make sense when graphs are (RDF) merged.

3/ Reification can be used for different claims about "the same thing" 
(a triple with the same appearance).

<<:moon :color "Green">> :saidBy :Bob ;   :saidOn "Tuesday" .
<<:moon :color "Green">> :saidBy :Alice ; :saidOn "Monday" .

This latter case can't be done with a single term for the {:moon :color 
"Green"} triple - the different properties get mixed up. Yes - better 
modelling is possible

<<:moon :color "Green">> :about [ :saidBy :Bob ;   :saidOn "Tuesday" ] .
<<:moon :color "Green">> :about [ :saidBy :Alice ; :saidOn "Monday"  ] .

Likewise, clashes happen when two RDF* graphs are merged. (Similar 
things happen in RDF graphs as well on a lesser and better understood 
level.)

     Andy

On 06/08/2019 16:12, Olaf Hartig wrote:
> Hi Kingsley,
> 
> On Mon, 2019-08-05 at 13:52 -0400, Kingsley Idehen wrote:
>> [...]
>> Under what circumstances in the real-world would the condition you model
>> arise i.e., propositions that don't manifest as part of documentation?
> 
> For instance, we my want to capture that Alice told us that Bob's age is
> 23, even if we don't have a document from Alice with this
> statement/claim regarding Bob's age.
> 
> Another example: we may want to capture that we do not believe that
> Bob's age is 23, which is independent of whether there exist a document
> making the claim about Bob's age or not.
> 
>> All sentences/statements are inscribed to documents that have provenance
>> oriented properties such as date, time, author etc..
>>
>> What I am trying to articulate here is that its a combination of the
>> sentence and document (in which they are inscribed) that brings
>> authority (or lack thereof) to a proposition represented as an RDF
>> sentence/statement.
>>
>> The triple:
>>
>> @prefix : <#> .
>>
>> :bob foaf:age "23"^^xsd:integer .
>>
>> Exists in a document identified by <> , so we a missing the following part
>> of reality (as I understand it):
>>
>> @prefix : <#> .
>>
>> <> a foaf:Document .
>> <> :creator :i .
>> <> :createdOn "2019-08-05"^^xsd:date .
>> <> foaf:primaryTopic :bob.
>>
>> :bob foaf:age "23"^^xsd:integer .
>>
>>
>> Thus, it's the authoritative weight given to <>, by whoever, under whatever
>> situation and circumstance, that leads to acceptance or rejection of the
>> claims outlined e.g., those about the foaf:age of the entity identified
>> by :bob .
> 
> I am not questioning that. Note, however, that your document is not
> making a statement/claim about the claim regarding Bob's age (other than
> asserting it, of course). The purpose of RDF*, and of RDF reification,
> is to allow you to do so (within your document or within another of your
> documents).
> 
> Best,
> Olaf
> 
>>
>> If we get the world we a modeling for clear, other bits of the problem
>> will become clearer.
>>
>> Conclusion:
>>
>> In my opinion, we need a complete example that's relatable to the world
>> that we are describing using RDF sentences :)
>>
> 
> 
Received on Friday, 9 August 2019 13:32:08 UTC

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