Re: The way forward

Niklas,


I am drawing a distinction between making statements about a specific statement and making statements about a collection of statements.  I think it is a mistake to consider the latter simple a more general version of the former.  The ability to have metadata about a specific statement is the key enabler (Statements about Statements) for edge properties (for RDF, leaving LPG out of this), statement level provenance for RDF, etc.


The ability to make statements about statement sets is different.  It does not support this basic mechanism of describing a specific statement unless a constraint is imposed such that the "Graph" is a single statement.


I think that talking about this as Statements about Statements (SAS) vs Statements about Graphs (SAG) highlights the difference.


The risk here is that people see SAG as more general, but in fact it is unable to support SAS without some constraint (e.g., a well-formedness constraint, a profile, etc.).


It was these SAS use cases that motivated RDR, RDF*, and the creating of this working group.


I am happy to see the WG support both, but let's not forget the motivating use cases of SAS.


Bryan

________________________________
From: Niklas Lindström <lindstream@gmail.com>
Sent: Friday, April 26, 2024 12:26:45 AM
To: Thompson, Bryan
Cc: Peter F. Patel-Schneider; public-rdf-star-wg@w3.org
Subject: RE: [EXTERNAL] The way forward

CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.



Bryan,

1.How come, given this:

    <e1> rdf:reifies <<( <s1> :p1 <o1> )>> .
    <e1> rdf:reifies <<( <s2> :p2 <o2> )>> .

you say that we're making statements about a graph, whereas with:

    <e1> rdf:reifies <<( <s1> :p1 <o1> )>> .

we are not? With your notion. how would you make statements about a
graph of only one triple?

Also, would you say that here:

    <john> foaf:knows <jane> .
    <john> foaf:knows <mary> .

we are making statements about the set of <jane> and <mary>? Does
<john> know that set? Does the set contain two persons, or two IRIs?

I suspect that in the sentence "making statements about a graph" there
is an unwitting change of context, from the domain of discourse to its
representation (which are not necessarily different, but quite often).

2. I'm not entirely sure what you mean by "making statements about
statements". From [1]: "Asserting an RDF triple says that some
relationship, indicated by the predicate, holds between the resources
denoted by the subject and object. This statement corresponding to an
RDF triple is known as an RDF statement." But then you talk about
triples, and graphs, i.e. sets of triples. Do you consistently refer
to the triple (the encoding) or the statement denoted by the triple
(the expression)? I would say we're making statements about
statements, by asserting triples where the object is another triple.
Many-to-one or many-to-many does not change that.

See also [2]: "An RDF triple encodes a statement—a simple logical
expression, or claim about the world. An RDF graph is the conjunction
(logical AND) of its triples."

Aside: Considering [3]: "An RDF graph is a set of RDF triples", I
don't think this working group is in agreement on whether a graph is
EXACTLY a set of triples (i.e. by definition, these two names denote
the same mathematical concept), or if a graph is a set of triples, but
not all sets of triples are graphs. (And here I do not mean "named
graphs" at all, which is a pair of a name (IRI or bnode) and this
graph notion. Of course, I do not know if that's supposed to mean all
such pairs; but that's hopefully beside the point...)

We may want to address these matters in today's semantics meeting.

Best regards,
Niklas

[1]: <https://www.w3.org/TR/rdf12-concepts/#resources-and-statements>
[2]: <https://www.w3.org/TR/rdf12-concepts/#entailment>
[3]: <https://www.w3.org/TR/rdf12-concepts/#section-rdf-graph>



On Fri, Apr 26, 2024 at 1:07 AM Thompson, Bryan <bryant@amazon.com> wrote:
>
> I do not believe that you answered my question Peter.   What do you want to call that set of Subject Predicate Object tuples?  At any rate, I will call it a graph and your proposal is making statements about those sets.  E.g., Statements about Graphs.
>
>
> Bryan
>
> ________________________________
> From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
> Sent: Thursday, April 25, 2024 4:04:46 PM
> To: public-rdf-star-wg@w3.org
> Subject: RE: [EXTERNAL] The way forward
>
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
>
>
>
> This is a fundamental misconception.  Consider complex numbers.  They are an
> ordered pair of real numbers, but there is no way that every ordered pair of
> real numbers has to be considered a complex number.  Similarly a set of RDF
> triples, let alone several RDF triples not collected into a set, is not
> necessarily an RDF graph.
>
> peter
>
>
> On 4/25/24 13:48, Thompson, Bryan wrote:
> > What do you call a set of S, P, O tuples?  I call it a Graph.  Your proposal is to reify such sets.  Hence, Statements about Graphs.
> >
> > Bryan
>