Predicates and Arcs vs Triples RE: use/mention and reification: rdf:predicate/subject/object

Graham Klyne wrote:
>
>
> At 09:16 AM 5/27/01 -0400, Jonathan Borden wrote:
...One can
> >refer to a statement that either is or is not asserted within a
> particular
> >context.
>
> I think it is useful to recognize the distinction, though I'm still
> inclined to believe it can be adequately captured in triples, given an
> appropriate approach to the semantics of reification.

Triples _can_ using sufficient contortions, capture the information. So can
strings of "1"s and "0"s. Yet although we can ultimately describe many
computations in terms of Turing Machines, it is most often not the most
useful form of description.

>
> >Another point: CWM does not use triples rather quads.
> (p,s,o,context) so it
> >appears this intellectual barrier of the arc being a triple has
> already been
> >broken ... indeed numerous implementations/APIs do not deal with base
> >triples. [...]
>
> I accept your arguments for the efficiency of representations based on a
> richer structure than triples, but I'd also point out that these
> efficiency
> considerations are largely implementation concerns.  I myself have
> previously discussed non-triple based representations, but I have also
> been  clear that these can be grounded (are mappable to/from) a
> triple-based form.

This argument is oft stated. And in the early days of software, similar
arguments were made regading the lack of ability of a high level language to
express anything beyond what is expressed in machine language.

Again and again: suppose we accept the fact that n-ary predicates can be
mapped to 1-ary predicates. wonderful.

Now lets move on to the task of describing things in the most natural
fashion. The endless arguments regarding reification, contexts, containers
etc. in _RDF_ are largely (IMHO) a direct result of the crippling of RDF
syntax by the imposition that all statements must be asserted as triples.

The proof of this assertion is held in the volumes of mailing list
discussions over years.

>
> I think their is a fair community investment in the triple form, and that
> it should not be discarded unless we are certain that it is fundamentally
> inadequate.

I submit that the community investment is in _arcs and nodes_ not triples
per se.

For example:
Grasper c. 1981: the concept of "space" is what you call a "context"
You: contexts e.g. (p,s,o, context)
TimBL: CWM/N3 same (p,s,o, context)
Megginson: RDFHandler either a quad or pentuple.
BWM: Jena: accepts RDFHandler statements as input

What we are calling "triples" are often not triples (of course they can be
decomposed into triples).

Jonathan Borden
The Open Healthcare Group
http://www.openhealth.org

Received on Sunday, 27 May 2001 13:53:14 UTC