# Re: defining RDF graph syntax

From: Dan Connolly <connolly@w3.org>
Date: 28 Oct 2002 18:05:26 -0600
To: Pat Hayes <phayes@ai.uwf.edu>

Message-Id: <1035849927.25017.5638.camel@dirk>
```
On Mon, 2002-10-28 at 17:32, pat hayes wrote:
>
> Guys, I know I said I would alter the MT to conform to the other
> docs, but after reading the other docs and the incoming comments, I
> really think that it might be worth standardizing on the simpler view
> of the RDF graph syntax that we already had worked out. Let me
> suggest that we all say some verbal variation on the following.

> 1. An RDF graph is a set of triples. That is the basic definition.
>
> 2. a triple consists of three parts A B C where B is a uriref, A is a
> uriref or a blank node, and C is a literal-thingie, uriref or blank
> node.
>
> 3. We call them 'graphs' because they have a natural graphical (ie
> pictorial) rendering as a collection of nodes and arrows with labels
> written on them. But we are careful not to say that they ARE graphs
> in any mathematical sense, because they aren't.
>
> 4.. As far as the syntax is concerned, blank nodes are just anonymous
> syntactic 'things'. They are rather like existentially quantified
> variables in logic, but one can also just think of them as blobs that
> are used to connect the graph together.
>
> 5. Linear notations like Ntriples and XML use bnodeIDs to keep track
> of the blobs, but those ID s shouldn't be thought of as names or
> references, and they are local to a particular document.
>
> The basic point of this is that it does NOT distinguish between nodes
> and their labels, and this is a real advantage, I suggest, in keeping
> the exposition clear. It certainly avoids what is otherwise going to
> be a minefield of getting the exact mathematical sense of 'graph'
> correct, and since we don't need to go into this minefield, I suggest
> that we keep out of it. In an earlier draft of the MT doc I had an
> appendix which really did use graph-theory notions to explain the
> syntax, and it was unreadable.
>
> It is fine to be informal and talk about 'labels' in the primer (or
> anywhere else) as long as one is careful to say somewhere that since
> two nodes never have the same label, that we can (and do) *formally*
> equate labelled nodes with their labels.
>
> Pat
>
> PS. I could try to draft rewordings/patches if other editors felt it
> might be useful, but I don't want to tread onto sacred ground or
> anything. I think it can all be done with a few sentences here and
> there, unless anyone really *wants* to get persnickety about
> distinguishing references to a node from references to the label of
> that node.
>
>
>
> --
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--
Dan Connolly, W3C http://www.w3.org/People/Connolly/
```
Received on Monday, 28 October 2002 19:05:11 UTC

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