- From: Mike Dean <mdean@bbn.com>
- Date: Thu, 25 Oct 2001 12:29:05 -0400
- To: Pat Hayes <phayes@ai.uwf.edu>
- cc: "Geoff Chappell" <geoff@sover.net>, www-rdf-logic@w3.org
> >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