RDF-CCK

That's interesting. Can you include a hand-made Graphviz graph that can illustrate what you have in mind?

for refererence, RDF CCK is http://drupal.org/project/rdfcck

This is a great idea, tracking. Interesting to note that drupal 7 core has some RDF features built in...

@deltab: Those example don't really clarify what you mean.

The way I see it, there are two ways that Graphviz Filter could interface with RDF: with RDF as input, and with RDF as output. If you want RDF as input, is there a particular reason to limit it to CCK? Might be useful to be able to deal with all RDF input data.

This seems to be basically the same overall idea as the graphviz-noderef module, just using RDF as input instead of noderef. Thing is, it's not hard to make nodereferences output RDF with RDF-CCK, and that might be a better way to go about graphviz-noderef, since it's far more extensible, and less reliant on understanding the plethora of modules based around the noderef concept.

Of course, this is still a bit speculative on my part, and I'm not commiting to going down this path (yet). One major question that I would have to answer before I decided to do this would be: Is the RDF data available to drupal modules BEFORE the page is rendered, or would the data have to be retrieved with an extra page call? I think I need to do some more reading about how RDF works...

First, the graphviz module is currently pretty focussed on Drupal data structures.

RDF, in the big view, is much wider than that. There may be space for a graphviz-rdf renderer, and now that graphviz.module is a bit more abstracted into a library than it was before, this could be built as a contrib.
A library that takes real RDF (eg the ARC Parser) and outputs graphviz surely exists already, outside of Drupal.
However, most graphs I've seen that try to express pure RDF are as ugly as hell, and don't really illustrate things very well.

What is not in evidence yet is a real Drupal-core to RDF mapping - although it's taking shape in D7, it's still not exactly useful yet. And CCK - if anything - would be constructed on top of that.
So we've got a box of pieces laid out in front of us, and they COULD be hammered together ... the question is - what are you actually trying to build here? The buzzwords are all in context, but what is the killer app that they produce? Currently it's all sandcastles.

@dman: the graphviz module just provides a way of converting .dot files into graphs in drupal. It's not focussed on drupal data structures - it's sub modules are. There's no reason we can't create other sub-modules that focus on data outside of the drupal structure - even from external websites.

Ugly as hell: yeah, that's true. Relationships' URIs and properties really need labels to make them pretty. RDF ain't there yet.

Sandcastles: I think it's a matter of if-you-build-it-they-will-come. HTML 1.0 was also crap, RDF will take a couple of versions to settle down. If we can get some basic stuff working - automated graphing of arbitrary relationship data - then we can refine it from there.