Re: My opinion of today on the profiles proposal


On 2 May 2024, at 09:07, Olaf Hartig <olaf.hartig@liu.se> wrote:

The reason why I ask is that I am still trying to get my head
around:
i) what exactly the kind of thing denoted by IRI :r in a triple
such as the following is:
( :r , rdf:reifies , ( :s, :p, :o ) )

It is anything which reifies--as in concretizes--an abstract
relationship; that relation being a simple logical expression as
encoded by a triple.

Thanks for this and the following explanations!

I assume that "that relation" in this sentence refers to the "abstract
relationship" mentioned in the first part of the sentence, right?

Regarding this and the following explanations of you, I am somewhat
struggling to understand the distinction between abstract relationships
and the more concrete things that the reifiers are supposed to be.

For instance, given a triple such as

( :r, rdf:reifies, (:bob, foaf:knows, :alice) ),

the 'knows' relationship between the resources denoted by the IRIs :bob
and :alice seems relatively concrete to me (ignoring philosophical
discussions of what it means to know someone). In what sense is the
thing denoted by :r more concrete / less abstract than this
relationship?

Let’s be technical, and rely on the formal semantics of RDF. Let’s focus on an interpretation of a RDF graph. And let me use the turtle concrete syntax, namely
:r rdf:reifies <<(:bob foaf:knows :alice)>>.

foaf:knows is a property which denotes a set of pairs of resources in an interpretation.

:bob foaf:knows :alice. is a triple, and it may be either true or false in an interpretation. The triple is a proposition, and it plays the role of truth-bearer.

<<(:bob foaf:knows :alice)>> is a triple term which denotes a resource in a interpretation. That resource is in one to one correspondence with the tuple formed by the denotation of the subject, predicate, object of the triple. In other words, that resource acts as the unique referenceable proxy for that triple, i.e., for the proposition represented by that triple - in a transparent way.

:r is a URI which denotes a resource in a interpretation. That resource (called “a reifier of the triple term”) is in a many-to-many relationship (rdf:reifies) with the triple term, namely with the proxy of the triple mentioned in the triple term. A reifier, with its existence, plays the role of truth-maker of the proposition (i.e., triple) it reifies, namely its existence supports the truth of the proposition. E.g., the existence of a specific wedding with its own properties supports the truth of the proposition claiming the truth of somebody marrying somebody else.

The same reifier may support the truth of different propositions: a specific wedding may support the truth of the proposition of somebody marrying somebody else, but also may support the truth of the proposition that somebody married in a certain location.

I hope this is clearer now,
Cheers
—e.