Re: Against the notion of reification well-formed graph (i.e., atomicity)

I’m not trying to be formal here...

> On 22. Jan 2024, at 20:46, Peter F. Patel-Schneider <pfpschneider@gmail.com> wrote:
> 
> The mapping from names to triples is not an injection, so there is no entailment (in an RDFS++ semantic extension of the syntactic sugar proposal) from
> 
> << :e | :s :p :o >> :a :b .
> << :f | :s :p :o >> :a :b .
> 
> to
> 
> :e owl:sameAs :f .
> 
> 
> To see this, just look at the expansion
> 
> :e rdf:type rdf:Statement .
> :e rdf:subject :s .
> :e rdf:predicate :p .
> :e rdf:oject :o .
> :e :a :b .
> :f rdf:type rdf:Statement .
> :f rdf:subject :s .
> :f rdf:predicate :p .
> :f rdf:oject :o .
> :f :a :b .
> 
> and notice that there is no entailment of
> 
> :e owl:sameAs :f .
> 
> Well-formedness has no role here.  All well-formedness says is that you can't mess up the reification structures, i.e., you can't add something like
> 
> :e rdf:subject :t .
> 
> to the above graph and retain well-formedness.
> 
> 
> I don't see how the following is a typical set of reification statements:
> 
> << :w1 | :bill-clinton :related-to :hillary-rodham >> :starts 1975 .
> << :w1 | :42nd-potus :husband :1st-female-NY-senator >> :starts 1975 .
> 
> This expands (using the base expansion) to something like:
> 
> :1w rdf:type rdf:Statement .
> :1w rdf:subject :bill-clinton .
> :1w rdf:predicate :related-to .
> :1w rdf:oject :hillary-rodham .
> :1w :starts 1975 .
> :1w rdf:type rdf:Statement .
> :1w rdf:subject :42nd-potus .
> :1w rdf:predicate  :husband .
> :1w rdf:oject :1st-female-NY-senator .
> :1w :starts 1975 .
> 
> which looks *very* weird to me.  I am not aware of any use of RDF reification that depends on the ability to have multiple subject, predicates, or objects.

IMO that’s not weird at all. Reification is referentially transparent, so why shouldn’t it be possible to add other IRIs that refer to the same entity?

However, the crucial detail is something else. :e and :f above do not *necessarily* refer to the same entity. They can be entailed to do so in the example above because no further detail is given. As soon as  e.g. provenance statements are added, their distinctness is established. 

One might argue that the act of creating two different reifications :e and :f, albeit with exactly the same set of attributes, in itself constitutes enough of a differentiating activity that the two IRIs can never be entailed to refer to the same entity. That however would’t harmonize with the whole design of RDF which favors establishing commonalities, not differences.

Thomas



> In the optional expansion there is no problem with two reifications having the same name but the expansion is different.
> 
> 
> peter
> 
> 
> On 1/22/24 10:51, Franconi Enrico wrote:
>> In this message I want to argue against the notion of reification well-formed graph (i.e., atomicity).
>> Adding atomicity violates a necessary aspect of the proposal (as written by pfps):
>> "There is no intended meaning of the new concrete syntax beyond what it expands to".
>> According to atomicity:
>> (1)
>> <<:a | :s1 :p1 :o1>> :s :o .
>> <<:b | :s2 :p2 :o2>> :s :o .
>> :s1 :same-as :s2 .
>> :p1 :same-as :p2 .
>> :o1 :same-as :o2 .
>> should entail
>> :a :same-as :b .
>> Atomicity adds an intended meaning: it assumes that the same triple has systematically the same identifier, and therefore (1) should be a valid entailment.
>> If you don’t like entailment (1), then you contradict the intention of atomicity, UNLESS you assume full opacity.
>> (2)
>> <<:a | :s1 :p1 :o1>> :s :o .
>> <<:b | :s2 :p2 :o2>> :s :o .
>> :a :same-as :b .
>> should entail
>> :s1 :same-as :s2 .
>> :p1 :same-as :p2 .
>> :o1 :same-as :o2 .
>> Atomicity adds an intended meaning: it assumes that a resource identifies at most one triple.
>> If you don’t like entailment (2), then you contradict the intention of atomicity, UNLESS you assume full opacity.
>> So, (1) and (2) show that _EITHER_ you assume full opacity (and therefore you are assuming an intended meaning), _OR_ you accept the above entailments (and therefore you are assuming an intended meaning).
>> Note also that entailments like the above make the life of SPARQL BGP matching more complex.
>> I also understand that most (if not all) use cases assume transparency.
>> (3)
>> Atomicity would disallow writing typical reification statements like:
>> << :w1 | :bill-clinton :related-to :hillary-rodham >> :starts 1975 .
>> << :w1 | :42nd-potus :husband :1st-female-NY-senator >> :starts 1975 .
>> cheers
>> —e.
>

Received on Monday, 22 January 2024 20:07:49 UTC