Re: Well-formedness for option 3

A better example, to avoid the temptation to believe that you may need owl:same-as:
<< :w3 | :bill-clinton :related-to :hillary-rodham >> :starts 1975 .
<< :w3 | :1st-female-NY-senator :wife :42nd-potus >> :starts 1975 .
Note that :related-to and :wife denote distinct properties.
—e.

> On 28 Feb 2024, at 10:27, Franconi Enrico <franconi@inf.unibz.it> wrote:
> 
> Indeed your property 2 is highly controversial and I have rejected it with all may energy in several past messages.
> An example:
> << :w3 | :bill-clinton :related-to :hillary-rodham >> :starts 1975 .
> << :w3 | :42nd-potus :husband :1st-female-NY-senator >> :starts 1975 .
> cheers
> —e.
> 
>> On 28 Feb 2024, at 10:23, Olaf Hartig <olaf.hartig@liu.se> wrote:
>> 
>> Thanks for the pointer Enrico! I was assuming that this document
>> defines only the semantics but I see now that you define a notion
>> of reification well-formed graphs at the end of this document.
>> 
>> I notice that this notion covers Property 1 of my definition (in the
>> email below), but not Property 2.
>> 
>> -Olaf
>> 
>> 
>> On Wed, 2024-02-28 at 09:09 +0000, Franconi Enrico wrote:
>>> As mentioned several times, you can find the current proposed
>>> formalisation of option 3 here:
>>> https://github.com/w3c/rdf-star-wg/wiki/RDF‐star-semantics%3A-option-3

>>> cheers
>>> —e.
>>> 
>>>> On 28 Feb 2024, at 10:03, Olaf Hartig <olaf.hartig@liu.se> wrote:
>>>> 
>>>> Dear all,
>>>> 
>>>> Do we have an email or a document with a definition of well-
>>>> formedness
>>>> in the context of option 3? I couldn't find any, but perhaps I
>>>> overlooked something.
>>>> 
>>>> The words “well-formed” and “well-formedness” were mentioned in
>>>> recent
>>>> calls that took place after the call in which we came to the
>>>> consensus
>>>> to focus on option 3. So, I assume that group members have an
>>>> understanding what the notion of well-formedness for option 3
>>>> means.
>>>> Yet, I couldn’t find any form of definition for it. The only
>>>> definition
>>>> that I found is the one of a “reification well-formed RDF graph” by
>>>> Peter [1], but that one is focused on options 1 and 2, and not
>>>> directly
>>>> applicable to option 3.
>>>> 
>>>> So, what is your understanding of a well-formed RDF graph in the
>>>> context of option 3?
>>>> 
>>>> Mine is as follows: An RDF graph is well formed iff it has all of
>>>> the
>>>> following properties.
>>>> 
>>>> - Property 0: None of the triples in the graph has a triple term
>>>> [2] as
>>>> its subject.
>>>> (In my reading of option 3, triple terms in the subject are already
>>>> ruled out by the abstract syntax itself, which makes mentioning
>>>> this
>>>> property here obsolete. Yet, I still mention it for the moment
>>>> because
>>>> some group members seem to argue for an abstract syntax in which
>>>> triple
>>>> terms may be used in the subject position.)
>>>> 
>>>> - Property 1: For every triple in the graph that has a triple term
>>>> as
>>>> its object, the predicate of this triple must be rdf:nameOf.
>>>> (I understand that the name of this predicate IRI is still under
>>>> discussion.)
>>>> 
>>>> - Property 2: For every pair of triples in the graph, if both
>>>> triples
>>>> have a triple term as their object (and, thus, have rdf:nameOf as
>>>> their
>>>> predicate, as per the previous point above) and these two triple
>>>> terms
>>>> are different from one another, then the two triples must not have
>>>> the 
>>>> same subject.
>>>> 
>>>> I assume that Property 2 might be controversial. It has the
>>>> disadvantage that merging two well-formed graphs may result in a
>>>> graph
>>>> that is not well formed according to the notion of well-formedness
>>>> with
>>>> Property 2 included. However, well-formedness without Property 2
>>>> makes
>>>> implementations that focus on efficient support for well-formed
>>>> graphs
>>>> significantly harder; I mean, without Property 2, such
>>>> implementations
>>>> cannot employ data structures (e.g., indexes) that assume that the
>>>> subjects of rdf:nameOf triples functionally determine the triple
>>>> terms.
>>>> Notice also that Property 2 is essentially the option-3 variant of
>>>> Peter’s aforementioned notion of a “reification well-formed RDF
>>>> graph”
>>>> for options 1 and 2.
>>>> 
>>>> An idea to eliminate the aforementioned disadvantage of including
>>>> Property 2 is to allow only blank nodes in the subject of
>>>> rdf:nameOf
>>>> triples, but that’s probably not very desirable either because it
>>>> would
>>>> mean that “occurrences” cannot be named by an IRI. Still, I thought
>>>> I
>>>> should mention this idea as a possible option to address the
>>>> undesirable effect on graph merging that Property 2 would imply.
>>>> 
>>>> Best,
>>>> Olaf
>>>> 
>>>> [1] 
>>>> https://github.com/w3c/rdf-star-wg/blob/main/docs/sugar-proposal.md#criticisms-and-responses

>>>> 
>>>> [2] 
>>>> https://pr-preview.s3.amazonaws.com/w3c/rdf-concepts/pull/78.html#dfn-triple-term
>>>> 
>>> 
>>> 
>

Received on Wednesday, 28 February 2024 09:31:48 UTC