defining RDF graph syntax

From: pat hayes <phayes@ai.uwf.edu>
Date: Mon, 28 Oct 2002 17:32:05 -0600
Message-Id: <p05111b15b9e3736c1e35@[65.217.30.130]>

```
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

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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```
Received on Monday, 28 October 2002 18:32:18 UTC

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