Re: Unified proposal for embedded triples (as per today's meeting)

Dear Enrico,

I would like to raise the concerns I already had during the meeting. It was a little bit unfortunate, that we could not directly discuss.

First of all: you keep asking why we went for the syntactic predication as you call it when we first defined the semantics of RDF-star. The reason for that was, that in some sense it was the strictest semantics: If we include the syntax  representation in our model, we can still make definitions ignoring the representation. If the representation is not respected in the theory in the first place, there is no way to take the syntactic representation of a triple into account and to cover the provenance case. We did not want to go for different semantics because we were afraid of creating some kind of „zoo“ where potential users could get lost. But I guess we should not make assumptions on the potential users of RDF-star and instead consider the use cases. These should be the base of our discussions.

Now to my concern: As I understand your semantic predication example and the semantics I have seen so far, it still takes the triple structure of the quoted triple into account and thereby relies on a syntactic feature. So, if we have that :teaches is an equivalent property to :givesClass (and if equivalent property is  covered in our semantics), we can still conclude that from

<< :john :teaches :cs101 >> rdf:type :teaching ;
                          dct:Location dbr:Stanford_University ;
                          dct:PeriodOfTime :1st-term-2022 .
:john :teaches :cs101.

that

<< :john :givesClass :cs101 >> rdf:type :teaching ;
                          dct:Location dbr:Stanford_University ;
                          dct:PeriodOfTime :1st-term-2022 .
:john :teaches :cs101.

We can do similar things with the subject and the object of the triple if we know that they are equivalent to other triples. But what happens if we have that the whole triple is equivalent to another one? For example, if we know that

:john :teaches :cs101.

and

:cs101 :isTaughtBy :John.

have the exact same meaning. How would we get that

<< :cs101 :isTaughtBy :John. >> rdf:type :teaching ;
                          dct:Location dbr:Stanford_University ;
                          dct:PeriodOfTime :1st-term-2022 .

It does not follow directly from the current semantics. Would you want to derive that? If not, we are in a strange situation where we have some partial reasoning going on in our quoted triples and if we keep it like that, the syntactical structure influences the behavior and that is somehow the prize we pay by connecting our semantics to reification. So, I would argue here, that if we want to take the triple structure, a syntactic property, into account, it is more natural (I know: highly subjective!) to base the semantics also on only the syntax level.

So, I assume that you want the derivation and I would like to see how you see it.

As an open question, I would also like to know, how you’d deal with logical consequences. So, what if :teaches is a sub property of :isInvolvedInCourse. Would we get any derivation triple containing a quoted triple or not? Do we want

<< :john :isInvolvedInCourse :cs101 >> rdf:type :teaching ;
                          dct:Location dbr:Stanford_University ;
                          dct:PeriodOfTime :1st-term-2022 .
:john :isInvolvedInCourse :cs101.

For this last example I have no opinion yet (apart from: no would be easier) and I think it would depend on the use cases. So,  to keep it open: how far should our referential transparency go?

Kind regards,
Dörthe

Am 03.03.2023 um 08:29 schrieb Franconi Enrico <franconi@inf.unibz.it<mailto:franconi@inf.unibz.it>>:

Hi Olaf,
sure, no problem, I’ll work on that.
—e.

On 3 Mar 2023, at 01:04, Olaf Hartig <olaf.hartig@liu.se<mailto:olaf.hartig@liu.se>> wrote:

Hi Enrico,

I want to pick up on the first question that Ora asked you during today's call and turn that question into a request
(not only to you but to the group in general).

I would very much prefer if proposals such as this one are presented not only in terms of an extension of Turtle (or any
other concrete syntax for representing RDF graphs) but also in terms of some structure or model that is defined using
mathematical concepts (e.g., sets, tuples, functions) and that expressions made in the concrete syntax can be mapped to.
I mean, the notion of an RDF graph [1] is such a structure, and so is the notion of an RDF-star graph [2]. I would like
to see definitions of such types of notions to be the basis of any proposal. The reason being that the definitions of a
model-theoretic semantics and of a query evaluation semantics would build on such notions (and not on expressions made
in the concrete syntax).

So, in this sense, what kind of a thing is it that you propose to write in the following form?

|<< :john :teaches :cs101 >>| :recorded "2021-07-07"^^xsd:date .

Similarly, what kind of thing would be written using the following form?

<< |:john| |:teaches| |:cs101| >> :recorded "2021-07-07"^^xsd:date .


Olaf

[1] https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.w3.org%2FTR%2Frdf11-concepts%2F%23dfn-rdf-graph&data=05%7C01%7Cfranconi%40inf.unibz.it%7Ccb27093faf804a68836d08db1b7ad0c8%7C9251326703e3401a80d4c58ed6674e3b%7C0%7C0%7C638133986518402021%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=6y47Df2e6Wz3xmb2eNQWbXCC32VPcyQpfmEAInNUs70%3D&reserved=0

[2] https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fw3c.github.io%2Frdf-star%2Fcg-spec%2F%23dfn-graph&data=05%7C01%7Cfranconi%40inf.unibz.it%7Ccb27093faf804a68836d08db1b7ad0c8%7C9251326703e3401a80d4c58ed6674e3b%7C0%7C0%7C638133986518558077%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=KxUl%2F0CLbYQxrKRapgY%2FWpM6K8hJGME24p1XGMm8jBM%3D&reserved=0



On tor, 2023-03-02 at 17:59 +0000, Franconi Enrico wrote:
Semantic predication example:

<< :john :teaches :cs101 >> rdf:type :teaching ;
                          dct:Location dbr:Stanford_University ;
                          dct:PeriodOfTime :1st-term-2022 .
:john :teaches :cs101.

Syntactic predication example:

|<< :john :teaches :cs101 >>| rdf:type unstar:triple ;
                            :recorded "2021-07-07"^^xsd:date .

or

<< |:john| |:teaches| |:cs101| >> rdf:type unstar:triple ;
                                :recorded "2021-07-07"^^xsd:date .

Modal/epistemic predication example:

<< :john :teaches :cs101 >> rdf:type unstar:statement;
                          :accordingTo :employee22 .