Re: Is <> a legal way to self-reference a named graph in a dataset in TriG?

Hi Thomas,

(NB: I changed the order of your text to make my answers more structured 
and, hopefully, easier to follow)

On 17/09/2022 06:59, Thomas Lörtsch wrote:
> Dear list,
>
> another question, and the last one for today, promise!
>
>
> I’m under the impression that in N3-ish RDF serializations the pair of pointy brackets <> refers to the current document, i.e. [0]
>
>     <> :type :eMail
To be more precise, <> resolves to the current base IRI, which defaults 
to the IRI of the current documebut can be overridden (e.g. using @base 
in Turtle / TriG).
> And is this all just convention (and up for debate) or is it defined somewhere? The syntax doesn’t seem to be part of SPARQL, Turtle or TriG.

Of course it is! This is just a special case of the IRIREF production in 
Turtle and friends:

   [18]     IRIREF     ::=     '<' ([^#x00-#x20<>"{}|^`\] | UCHAR)* '>'

where the content of the pointy brackets is allowed to be empty (the 
empty string is a valid relative IRI).

> And what about TriX, RDF/XML even, JSON-LD? Do they provide a means to self-reference the current graph itself?
in TriX: <uri></uri>
in RDF/XML: rdf:about=""
in JSON-LD: @id=""
> But what about named graphs in RDF 1.1? In a named graph, contained in a dataset, does '<>' refer to the named graph itself, or to the enclosing dataset?

This question does not really make sense, because it mixes elements of 
the abstract syntax (named graph, dataset) and elements of the concrete 
syntax (the empty relative IRI).

Remember that in the abstract syntax, all IRIs are absolute. Relative 
IRIs must be resolved to absolute IRIs when parsing the concrete 
synytax. I hope that my explanations above make it clearer.

Following this,  the following TriG file located at http://ex.co/test.trig


   PREFIX s: <http://schema.org/>
   GRAPH <#foo> {
       <> s:name "Bar".
   }

would produce the same dataset as the following N-quad:

   <http://ex.co/test.trig> <http://schema.org/name> "Bar" 
<http://ex.co/test.trig#foo>.

best

>
> Best,
> Thomas
>
>
>
> [0] The example glosses over the fact that the rest of this document is not valid RDF. A similar example can be found in the heading of <http://infomesh.net/2002/notation3/>