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Re: owl:sameAs/referential opacity Re: Can RDFstar be defined as only syntactic sugar on top of RDF (Re: weakness of embedded triples)

From: Pierre-Antoine Champin <pierre-antoine.champin@ercim.eu>
Date: Thu, 19 Nov 2020 16:12:56 +0100
To: thomas lörtsch <tl@rat.io>
Cc: public-rdf-star@w3.org
Message-ID: <6522d956-c349-56b0-2443-edd8ce00018d@ercim.eu>
On 19/11/2020 12:41, thomas lörtsch wrote:

>> On 18. Nov 2020, at 15:07, Pierre-Antoine Champin <pierre-antoine.champin@ercim.eu> wrote:
>> On 17/11/2020 23:18, thomas lörtsch wrote:
>>> Just a quick check:
>>>> On 17. Nov 2020, at 18:11, Pierre-Antoine Champin <pierre-antoine.champin@ercim.eu> wrote:
>>> […]
>>>>> +
>>>>> Both "modes" used side by side would solve this problem:
>>>>> 	<< :a :b :c >> :denies :d .
>>>>> 	:a :b :c {| :exclaims :e |}
>>>> No, because his concrete syntax would produce exactly the same abstract syntax as your previous example -- at least in my understanding, but I trust that Olaf would agree (see https://github.com/w3c/rdf-star/issues/9#issuecomment-708608422).
>>>>  From the very beginning, embedded triples in RDF* are totally identified by their subject+predicate+object, there is now way to distinguish different mentions (tokens) of the same triple.
>>> You mean
>>>>> 	:a :b :c {| :d :e |}
>>> is meant to annotate all triple tokens of type
>>> 	:a :b :c .
>>> everywhere, anywhere?
>> As Peter pointed out in his reply, RDF* does not have any notion of "triple token", only that of "triple type" (so to speak).
>> So the example above is not "meant to annotate all triple tokens", but meant to annotate this one triple (type).
> This answer doesn’t help me as in my terminology "triple" and "triple (type)" refer to very different things.
Yes, that's why I put "type" in parenthesis.
>   Let’s try another terminology: types of triples versus occurrences of triples. A triple of type
> 	:a :b :c .
> can occurr in different graphs. Graphs are defined as sets of triples and therefor any triple can occurr only once per graph.


> Imagine the following RDF* graph, consisting of only one annotated statement:
> 	:a :b :c {| :d :e |}
> Does the annotation ':d :e' annotate
> 1) that specific occurrence of ':a :b :c' in the same graph or
> 2) some occurrence of ':a :b :c' but it doesn’t define which or
> 3) any occurrence of ':a :b :c' in all graphs ?
> I assume it’s option 2 but I’m not sure.

For me the answer is:

4) it annotates the triple type itself

And annotating the type is not the same thing as annotating one or 
several occurrences -- just like annotating a set is not the same as 
annotating one or several of its elements...

> Thomas
>>>> As I understand, this was a deliberate design choice.
>>> And with what rationale?
>> I can't talk for Olaf. My guess is that it was deemed simpler, and sufficient for most use cases.
>> Maybe also it was considered as the less disruptive change to RDF. Consider the following Turtle:
>>    :a :b :c, :x.
>>    :a :b :c, :y.
>> The two occurrences of ":a :b :c" in that concrete syntax are "squashed" into the same triple in the abstract syntax. RDF itself does not distinguish different tokens of the same triple. Why should RDF*?
>> Finally, if you want to track different "utterances" of the same triple, nothing prevents you to write
>> :a :b :c {|
>>    :utterance [ :by :alice; :on "2020-11-10" ],
>>      [ :by :bob; :on "2020-11-13" ]
>> |}
>>> Thomas
>> <OpenPGP_0x9D1EDAEEEF98D438.asc>

Received on Thursday, 19 November 2020 15:13:02 UTC

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