Re: Proposal for RDF-star Minimal Baseline - Agenda item for this week's plenary

Hi Dörthe,
I’m happy you bring us your comments.

- injectivity of RE: in my opinion there is no real reason to make the function injective and I think it could cause harm in the sense that such restriction can lead to inconsistencies when we extend the logic.  I guess that was discussed in a task force meeting I was not present? Maybe I can read it up somewhere?

It is true that injectivity could cause harm in extensions. That’s why we created the well-formed fragment, and we expect that extensions should only consider the well formed fragment (where there are no isolated triple terms). In fact, injectivity of the denotation of a triple term is harmless if we restrict ourselves to the well formed fragment.
We can not drop injectivity, since the semantics of a triple term would be wrong. The resource denoted by a triple term should be unique, since it represents the (unique) semantics of the triple in the interpretation - it is the “type". It would be not faithful to have a triple term denoting different resources in an interpretation: what would the additional resources represent? That’s what model theory is about, namely to reconstruct interpretations (“models”) which faithfully represent the intended world; here, in the world there is a unique meaning for a triple term.

- semantics of triple terms: in your abstract syntax, the :a :b :c in your triple :s :p << :a :b :c>> is a triple and a triple term at the same time, in my opinion, it is therefore not clear that the [I+A](t.o) in the interpretation  [I+A](t) of the overall triple refers to the term interpretation and not the triple interpretation. I think that should be stated more clearly. We should emphasize the difference between a triple and a triple term.

You are right. I have to fix the syntactic categories used in the grammar.

- well-formed semantics: I don’t think that it really works make the restriction on rdf:reifies as you currently do it in the well-formed syntax. As I have RDFS, I could declare:

doerthe:reifies rdfs:subPropertyOf  rdf:reifies.
rdf:reifies rdfs:subPropertyOf  doerthe:reifies.

Now, I have a predicate doerthe:reifies which behaves like rdf:reifies and this makes the restriction not really strong (thinking about it, it is interesting, that I(rdf:reifies) and I(doerthe:reifies) can still differ). I think we could drop the restriction, but I also did  not fully understand the reason for having it in the first place, maybe you can explain?

For the same reason that in RDFS we give a special meaning to rdf:type in defining the extension of classes: only rdf:type gives meaning to the extension of classes and this is explicit in the meta model. Similarly to your case, I could create a fake pseudo-equivalent predicate doerthe:type, but this would not be explained by the meta model and would not have a role in defining a class.

We can still keep that triple terms may only be in the object position of rdf:reifies, even though, I dislike that (I think I already explained why, mainly because I want to be able to express all logical consequences, but that is a separate topic).

I don’t follow here.

- we should start to think about all the RDF meta modeling stuff, because I am curious whether that could lead to problems especially in combination with the well-formed semantics

I violently agree.

cheers
—e.

Kind regards,
Dörthe

Am 16.07.2024 um 19:20 schrieb Adrian Gschwend <adrian.gschwend@zazuko.com>:

Dear group,

During the recent Semantics Task Force call, there was an informal agreement to propose a resolution for the main group [1]. The proposed resolution is to implement the minimal baseline for RDF-star as outlined in the following document: RDF-star "minimal baseline" [2].

The chairs (Ora and I) have discussed this matter and we support bringing this topic to the main group for a formal resolution.

We would like to add this proposal to the agenda for this week's meeting. Additionally, we request that a representative from the Semantics TF present this proposal to the group. Ideally, this could be done via email prior to the meeting to ensure everyone has the opportunity to review and prepare for the discussion.

regards

Ora & Adrian

[1]: https://www.w3.org/2024/07/12-rdf-star-minutes.html

[2]: https://github.com/w3c/rdf-star-wg/wiki/RDF-star-%22minimal-baseline%22


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Adrian Gschwend
CEO Zazuko GmbH, Biel, Switzerland

Phone +41 32 510 60 31
Email adrian.gschwend@zazuko.com