Re: Slides: Talking About Occurrences

Niklas,


A few comments about your slides (not necessarily about your proposal):

First, the good things: RDF reification is indeed under-used, but it is 
used. Especially, it has been used in significant datasets like uniprot 
when the default syntax for RDF was RDF/XML. RDF/XML has syntactic sugar 
for reification, which makes it super easy to write. One reason people 
don't like reification is because it is verbose and cumbersome. But RDF 
lists are also verbose and cumbersome if written as triples. Yet, with 
the right syntax, good practices, and dedicated primitives in 
programming, they are well accepted and well supported. The same could 
be true with reification. So, yes, "quoted triples" as a way to simplify 
the use of standard RDF reification is an option that should be on the 
table. But the big problem is that the semantics is not constraining at 
all, and people may have completely different practices in the way they 
use reification. However, as opposed to named graphs, RDF reification 
has a normative semantics, although it is very weak.


Second, the criticism, in details:

Slide 6 has the title "RDF 1.1 Concepts" and subtitle "on reification", 
but the text you put on the right is from RDF Schema. "Concepts" don't 
say anything about reification. Moreover, this text is in a section that 
is not normative. Formally, the semantics of reification does not imply 
that a reified triple is a token or anything. According to the standard, 
one could interpret a reified triple as the triple itself and it would 
not violate anything normative.

Then in Slide 7, what is written is Pat Hayes's idea of a named graph. 
But as far as the standards are concerned (SPARQL 1.0, SPARQL 1.1, and 
RDF 1.1), named graphs are *only* pairs (n,g) and that's all. You may 
interpret this as a token of a graph with a name if you want, but again, 
this is not normative and there are other ways to interpret it.

In Slide 24, it is written "A triple is identified with the singleton 
set containing it", and a subtitle says "RDF 1.1 Semantics". Clearly, an 
element and the singleton that contains it are never the same, but they 
may be identified in certain contexts. I do not understand to which 
context you refer here. The mention of RDF 1.1 Semantics is misleading 
because RDF 1.1 Semantics does not have this identification. In fact, 
quite the opposite: if they were identified, then:

{ <me> <wears> _:b . _:b a <Hat> }

would be identified with

{{<me> <wears> _:b}, {_:b a <Hat>}}

But these two sets mean different things. The second one does not imply 
the first one. First one says "I wear a hat", while second one says "I 
wear something. There exists a hat."

Slide 30: Again, "The <name, graph> pair is a token of its mathematical 
graph." is one way of interpreting the pair. Imagine I have a pair (iri, 
n), where iri is an IRI and n is a natural number. Would you interpret 
this as a token for the mathematical number n? For instance, instead, if 
iri is a DOI, n could be the number of times the document was printed.

Also, "This token, which is denoted by this name" is your 
interpretation. "Denote" is formally defined in RDF 1.1 Semantics: 
https://www.w3.org/TR/rdf11-mt/#dfn-denote, so when you use this term in 
the context of RDF, it suggests that you talk about what RDF Semantics 
says. But RDF Semantics does not say that the graph name denotes 
anything in particular.

Slide 34: I don't understand or I simply disagree with some of the 
statements: "...nested graphs? (...) Requires “graph literals” (...)" -> 
I don't see how this follows from that.

"… graph terms? Same problem as for triple terms -
these are abstract mathematical objects denoting
themselves." -> graph terms are just a syntactic structure. This does 
not imply anything about what they denote or not.



Additionally, there are parts where it is hard to understand what you 
mean. Your spoken words yesterday explained some things but sometimes 
even with your verbal presentation, I had trouble figuring out what your 
proposal(s) consist(s) in exactly.



--AZ

Le 26/10/2023 à 20:37, Niklas Lindström a écrit :
> Dear all,
> 
> Here are the slides I presented at today's teleconference.
> 
> Best regards,
> Niklas
> 
> (PS. Escher's Dragon is pixelated to avoid copyright issues.)

-- 
Antoine Zimmermann
École des Mines de Saint-Étienne
158 cours Fauriel
CS 62362
42023 Saint-Étienne Cedex 2
France
Tél:+33(0)4 77 49 97 02
http://www.emse.fr/~zimmermann/

Received on Friday, 27 October 2023 10:07:50 UTC