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Re: nodes and node labels [was New document: revised version for WG review]

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Mon, 29 Jul 2002 22:45:02 +0200
To: <w3c-rdfcore-wg@w3.org>
Message-ID: <MABBLGKMPIJFCKFGDBEPEEAHCBAA.jjc@hplb.hpl.hp.com>

I wanted to draw the WG attention, particularly Pat, to a mathematical issue
with the graph syntax.

I do not believe that this has any substantive content, but is merely

In the very first version of the model theory, the RDF graph was described
as having nodes some of which had labels, and the labels were URI refs or

In the most recent version, some of the nodes are URI refs and some of the
nodes are strings (and none of the nodes are labelled).

In the new document draft, we have reverted to the earlier version using
explicit node labels.

The motivations for this include:
- tidying a graph is an explicit operation rather than implicit by
mathematical construction
- it easier to modify the exact tidyness specification (if the WG changes
its mind about whether literals are tidy or not - uriref nodes don't seem in
- implementations will almost all use nodes with explicit labels.

The first point is the decisive one. From a mathematical point of view Pat's
latest model theory treatment in which the URI refs and strings *are* the
nodes is extremely elegant. Tidiness just falls out and no text needs to be
spent on it.
However, in practice any implementor needs to be aware of tidiness as an
operation which has to be coded, and any user needs some understanding of
tidiness. Thus, I felt that Pat's earlier treatment, while a little more
clunky, is clearer for our intended audience: implementators, users, web
architects - rather than mathematicians.

Although I raise this issue now, I would hope that any debate, if debate is
needed, can be postponed until after the first WD. I don't think this is a
crucial issue either way.

Received on Monday, 29 July 2002 16:39:52 UTC

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