[Fwd: Some questions about Named Graphs]

We had comment from Yuzhong ... he agreed that we could answer on
www-archive.
I'll send my reply, other comments welcome.

Jeremy



-------- Original Message --------
From: Yuzhong Qu <yzqu@seu.edu.cn>
To: <Jeremy_Carroll@hp.com>, <chris@bizer.de>
Subject: Some questions about Named Graphs
Date: Mon, 28 Jun 2004 18:12:09 +0800

Dear Jeremy and Christian,

I found the paper entitled "Named Graphs, Provenance and Trust" is
terrific good.

Some questions arised when I read the section 2 "Abstract Syntax and
Semantics" of this paper.

1. 5-tuple <N,V,U,B,L> where: U is a "set" of URIrefs; L is a "set" of
literals (both plain and typed); B is a "set" of ¡®blank¡¯ nodes; ......;N
is a "set" of pairs forming a partial function from U to V ¡Á U ¡Á V .

   Are they finite sets? I guess they should be.

  As to "N is a set of pairs forming a partial function from U to V ¡Á U
¡Á V", why not a partial function from U to P(V ¡Á U ¡Á V)? (The power set
of ...) because you use "partial function" instead of "partial mapping".

2. For ng, ng' belonging N with ng != ng'then the blank nodes used in
triples from rdfgraph(ng) are all distinct from those used in triples
from rdfgraph(ng'), i.e. blank nodes cannot be shared between different
graphs named in N.

What's the criteria to test ng = ng'? I guess it depends on the equality
of the first elements of the two pairs, i.e. whether or not name(ng) =
name(ng'), then it depends on the equality of URIrefs?

In addition, why you must require "the blank nodes used in triples from
rdfgraph(ng) are all distinct from those used in triples from
rdfgraph(ng')"?  I mean that the above requirement (or assumption) seems
redundant. Even worse, in some cases, two blank nodes within two
different graphs may be equal due to the fact that they have the same
value for an inverse-functional dataProperty (in OWL), or the two blank
nodes are equal to each other within some context.

3. Can a blank node denote a named graph (or graph)?

   If it can, how about the corresponding syntax?

4. As to the Namespace and RDF Schema:
xmlns:rdfg="http://www.w3.org/2004/03/trix/rdfg-1/"

   The class "rdfg:Graph" is to represent the concept of named graph,
graph, or other thing?

   I guess it's about named graph, then why not use the word "NamedGraph"?



Thanks for your concern!




Yuzhong Qu

Received on Monday, 28 June 2004 09:59:30 UTC