Re: Different properties related to well-formedness

Thanks Antoine! While I still find this phrasing a bit odd, I can live
with it (no need to start bike shedding here).

-Olaf



On Wed, 2024-04-24 at 18:16 +0200, Antoine Zimmermann wrote:
> Le 24/04/2024 à 17:10, Olaf Hartig a écrit :
> > Hi Antoine,
> >
> > I see your point and I am fine with changing the definition such
> > that
> > the notion of a 'triple term' refers to an RDF triple in the role
> > of
> > being an element of another triple---exactly as we had in the CG
> > report
> > (where we used the name 'quoted triple' instead of 'triple term').
> >
> > Of course, changing the definition of 'triple term' in this way
> > does
> > not have any impact on the syntactic properties that I am defining
> > in
> > the document (except that the repetition of some of the definitions
> > becomes obsolete as you point out).
> >
> > I have created a PR that implements these changes in the document:
> >
> > https://github.com/w3c/rdf-star-wg/pull/121

> >
> > However, let me ask you whether, assuming the definition approach
> > that
> > you propose, you would consider a sentence such as the following to
> > be
> > formally accurate?
> >
> > "Let (s,p,o) be an RDF triple in which o is a triple term."
> >
> > Or would an accurate way of phrasing the sentence be as follows?
>
> In this case, I think the context is clear because we are mentioning
> the
> triple term in the context of a well identified RDF triple, and it is
> in
> fact better at distinguishing the containing RDF triple and the
> contained RDF triple.
>
> > "Let (s,p,o) be an RDF triple in which o is an RDF triple."
> >
> > Similarly, for a triple such as (x, rdf:reifies, (s,p,o)), would it
> > still be accurate to say that "x reifies the triple term (s,p,o)" ?
>
> Similarly, I think that in any situation where an RDF triple plays
> the
> role of a triple term wrt a well identified RDF triple, this way of
> phrasing is appropriate because not only the context makes it clear
> what
> we mean, but also it makes it easier to distinguish 2 RDF triples
> under
> consideration.
>
> --AZ
>
> > Thanks,
> > Olaf
> >
> >
> > On Tue, 2024-04-23 at 17:59 +0200, Antoine Zimmermann wrote:
> > > Olaf, all,
> > >
> > > I have a problem with the way triple terms are sometimes defined
> > > in
> > > the
> > > different formalisations of RDF 1.2 (like the semantics proposed
> > > by
> > > Enrico and this well-formedness proposal).
> > >
> > > Considering your definitions, a triple term *is* an RDF triple.
> > > Not
> > > just
> > > syntactically. It *is*, in every aspect. A triple term should not
> > > be
> > > defined like this, because the phrase "triple term" denotes a
> > > different
> > > thing than the phrase "RDF triple".
> > >
> > > A triple term is a role an RDF triple plays within another RDF
> > > triple.
> > > Just like "predicate" is the role an IRI plays inside an RDF
> > > triple.
> > >
> > > Compare your definitions with these:
> > >
> > > Definition: An RDF 1.1 triple is a 3-tuple (s, p, o) where:
> > >    - s in an IRI or a blank node;
> > >    - p is a predicate;
> > >    - o is an IRI, a blank node, or a literal.
> > >
> > > Definition: A predicate is defined as:
> > >    - a Unicode character string that conforms to the syntax
> > > defined
> > > in
> > > RFC 3987
> > >
> > > Then one could say "let i be a predicate", which is very odd.
> > > Since
> > > i
> > > *is* a URI, I can then talk about the triple (i, p, o), and then
> > > there
> > > is a predicate in subject position!
> > >
> > > It is not difficult to distinguish the notion of predicate and
> > > the
> > > notion of IRI. One is a role in a triple while the other is a
> > > class.
> > >
> > > I claimed that it is not difficult to define triple terms in such
> > > a
> > > way
> > > that it is distinct from RDF triples, by making it a role that an
> > > RDF
> > > triple plays inside another RDF triple.
> > >
> > > Therefore, I would propose:
> > >
> > > Definition: An /RDF triple/ (or just /triple/ if context is
> > > clear) is
> > > a
> > > 3-tuple that is defined recursively as follows:
> > >    - If s is an IRI or a blank node, p is an IRI, and o is an
> > > IRI, a
> > > blank node, or a literal, then (s, p, o) is an RDF triple.
> > >    - If s is an IRI or a blank node, p is an IRI, and o is an RDF
> > > triple,
> > > then (s, p, o) is an RDF triple.
> > >    - If s is an RDF triple, p is an IRI, and o is an IRI, a blank
> > > node, a
> > > literal, or an RDF triple, then (s, p, o) is an RDF triple.
> > >
> > > Definition: the first (resp. second, resp. third) element of an
> > > RDF
> > > triple t is called the /subject/ (resp. /predicate/, resp.
> > > /object/)
> > > of
> > > t and if the subject (resp. object) of t is an RDF triple then we
> > > say
> > > that it is a /triple term/ for t. Likewise, any RDF triple that
> > > is a
> > > triple term for a triple term of t is also a triple term of t.
> > >
> > > Definition: the /triple terms of an RDF graph/ G are all the
> > > triple
> > > terms of the RDF triples that compose G.
> > >
> > >
> > > Using these definitions, you would also avoid the redundancy in
> > > the
> > > definitions of /triple-term-placement well-formed/ and
> > > /reifies-predicate well-formed/, which look very much like
> > > unintended
> > > duplicates.
> > >
> > >
> > > --AZ
> > >
> > >
> > > Le 23/04/2024 à 16:50, Olaf Hartig a écrit :
> > > > Hi all,
> > > >
> > > > It occurs to me that the notion of well-formedness that the
> > > > group
> > > > strives for has more facets than just the decision of whether
> > > > rdf:reifies is many-to-many or many-to-one, and I think it
> > > > would be
> > > > useful for us to be able to discuss and to decide about these
> > > > facets
> > > > independent of one another. Therefore, I have created the
> > > > following
> > > > document in which I define different syntactic properties that
> > > > an
> > > > RDF
> > > > graph with triple terms may possess, where each of these
> > > > properties
> > > > corresponds to one of the facets that I see. The important
> > > > point is
> > > > that these properties are completely orthogonal, and we can
> > > > decide
> > > > which of them we include as the properties required for well-
> > > > formedness.
> > > >
> > > > https://github.com/w3c/rdf-star-wg/blob/main/docs/constraints.md

> > > >
> > > > Best,
> > > > Olaf
> > > >

Received on Wednesday, 24 April 2024 16:57:29 UTC