RE: The mentography of reification

> -----Original Message-----
> From: www-rdf-logic-request@w3.org
> [mailto:www-rdf-logic-request@w3.org]On Behalf Of Pat Hayes
> Sent: Friday, October 26, 2001 5:17 PM
> To: Geoff Chappell
> Cc: www-rdf-logic@w3.org
> Subject: RE: The mentography of reification
>
>
> >  > -----Original Message-----
> >>  From: www-rdf-logic-request@w3.org
> >>  [mailto:www-rdf-logic-request@w3.org]On Behalf Of Pat Hayes
> >>  Sent: Wednesday, October 24, 2001 8:32 PM
> >>  To: Geoff Chappell
> >>  Cc: www-rdf-logic@w3.org
> >>  Subject: Re: The mentography of reification
> >>
> >>
> >>  >My understanding is that the triple can be thought of as defining a
> >>  >particular arc in a graph. That nodes and arcs have identities
> >>  (locations on
> >>  >a page, position in memory, or whatever) and labels.  That with the
> >>  >restriction that no two nodes can have the same label,
> >>
> >>  We may want to relax this slightly for literals; but otherwise, yes.
> >>
> >>  >  we can uniquely
> >>  >identify a node by its label. That with the restriction that
> duplicate
> >>  >triples can not exist, we can uniquely identify an arc by
> the nodes it
> >>  >connects (in order) and the label on the arc. (Nodes, I guess,
> >>  are asserted
> >>  >into existence by their use in describing an arc?)
> >>  >
> >>  >Taking that view, I'd always envisioned that a nested or
> reified triple
> >>  >would be shown on a graph as arcs originating or terminating on
> >>  arcs (though
> >>  >I don't know about the validity of that in graph-speak).
> >>
> >>  It isn't good graph-speak, and it isn't correct RDF either, so don't
> >>  think of it that way, I would suggest.
> >>
> >
> >Thanks for the suggestion :) But I can't help thinking there's something
> >clarifiying about that way of looking at it.
>
> Well, I think it is less than clarifying, though it may be possible
> to clarify it with some work.
>
> First, I'm not sure what you mean by 'arc'. If this is a piece of an
> RDF graph (drawn in ascii-art):
>
> nodeaaa ------ edgeccc------> nodebbb
>
> is that an arc? Or is THIS an arc?:
>
> ------ edgeccc------>
>
> ie does your 'arc' have three labels or one? If the answer is three,
> this is what is called a 'triple', and its the simplest reifiable
> statement in RDF. If this is what you mean, then indeed reification
> could be indicated by some such convention of arcs pointing to arcs,
> I agree

I was thinking of a triple as a syntactical structure made up of three
strings/labels that designated a particular arc in a graph (two identical
triples would refer to the same arc in the graph). I was thinking of a graph
as a collection of two types of objects, nodes and arcs. Nodes have two
intrinsic properties - a type and a label. Arcs have four intrinsic
properties - a type, a label, a reference to an object(node or arc), and a
reference to another object(node or arc). An arc could be visualized as a
labeled line between the two objects it references or as a labeled "node"
with lines between it and the nodes it references. Clearly an arc could not
be unamiguously designated by its label alone, though a node could (as long
as the node's label indicated the "type" - to allow one to distinguish
between the resource node "w3.org" and the literal node "w3.org").

I saw RDF (as it is today) as moreorless defining two types of nodes
(literals and resources) and one type of arc (asserted relationship). I
imagined that you could enable deeper structure in the future by surfacing
these implicit types and adding to them - so for example add a "unasserted
relationship, etc." type (and throw in some other intrinsic datatypes beside
literals/strings while you're at it).

When I said it seemed like clarifying - I meant that it seems like a
perspective in line with current thinking but that has a path for future
extension. Does that clarify what I was saying or did I muddy the waters
more?

>(though I can see no utility for arcs coming FROM arcs). I
> took you to be talking about the other idea, and I can see no real
> utility for that one.

Only that there's no reason not to allow one if you allow the other. Then
you could say:
{saidAt {isa fido dog} 12PM} as well as {says geoff {isa fido dog}}.

>[...]
>
> >To make it a valid picture I
> >suppose it requires elevating labeled arcs to nodes themselves with arcs
> >then just identifying the binary connections between nodes.
> Couldn't that be
> >considered an alternative visualization/representation?
>
> Well, that's pretty much what current reification does, right?

I don't think so - seems like the reification is using the system to
describe itself while viewing an arc as a node is changing/reinterpreting
the system to enable it to describe other structures.


>[...]
> >anticipate the rdf of tomorrow. How does the current graph
> conceptualization
> >of rdf handle deeper structures?
>
> The current conceptualization of RDF *doesn't* handle deeper
> structures. Let me return to my original question. Why should we
> care?

It seems that question can only be answered in the context of the goals of
RDF. Is that part of the current work of the WG - to clarify those goals? or
are they already clear to everyone but me?

Thanks for your helpful responses.

Geoff Chappell

Received on Friday, 26 October 2001 19:26:50 UTC