Re: The mentography of reification

> >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.

While it may not reflect graph theoretic purity, I think
"arcs on arcs" is a very useful model.

I expect knowledge bases where each "ground" statement has
at least one statement made about it (source, timestamp,
confidence, etc.).  Creating 4 additional statements
(current RDF reification) and still not being able to
directly associate those statements with the real statement
is impractical.

Representative applications include:

  genealogy databases (e.g. [1]) where the source of each
  fact is supposed to be documented (birth date and place,
  mother and father from birth certificate n at courthouse
  X; death date from tombstone at Cemetery Y; marriage from
  family Bible in possession of Z as of date d -- hopefully
  expressed as triples rather than text)

  web caches [2]

  intelligence databases (which include source, processing
  history, uncertainty, conflicting data, etc. potentially
  on a per-field level)

The RDF APIs I've used directly support using a statement as
the subject of another statement (see [3]), although the
serialized results vary.  I'd like to see this addressed
directly in the RDF specification so that it becomes a
generally useful capability.

I've seen a number of database models that are horrendously
cluttered by maintaining a timestamp, security
classification, audit trail, etc. with each field.  A
simple, general mechanism to accommodate such "tagging" (the
term some of us are using for the examples above, as opposed
to more general reification) could well be the most
compelling feature of RDF for many applications.

RDF M&S [4] hints at this usage

  Within propertyElt (production [6.12]), ... The value of
  the ID attribute, if specified, is the identifier for the
  resource that represents the reification of the statement.

but IMHO got hung up on using "quoting" rather than
"tagging" as the canonical example for reification [5].

	Mike

[1] http://www.daml.org/2001/01/gedcom/

[2] http://www.daml.org/homework/1/collected/README

[3] http://www.daml.org/2001/04/reification/

[4] http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/

[5] http://www.daml.org/listarchive/joint-committee/0274.html

Received on Thursday, 25 October 2001 12:29:55 UTC