The Heart of RDF Darkness from Eric Hellman on 1999-12-31 (www-rdf-interest@w3.org from December 1999) (original) (raw)

I agree this is confusing, it was referred to in an earlier discussion as "striping" of syntax. Implicit in the RDF syntax is the notion that something is either a property or a value. The parseType="Resource" attribute leads to confusion because it implies the creation of an anonymous resource. Having both rdf:ID and RDF:resource attributes is illegal because the parser can't decide whether it's a value or a property.

Another way to look at this is to asK if you have

then what does the ID identify? the statement, or the resource? I agree it would be convenient to have a separate ID for the reification, but perhaps that's nasty.

Presented with a similar problem to Jeff Sussna's, we explicitly made an intermediate object.

so Mick has sponsorship x (x is a Sponsorship object) x has startyear 1985 x has stopyear 1990 x has sponsorname pennzoil

So because RDF is property-oriented, we end up creating lots of objects.

At 3:40 PM -0800 12/30/99, Gabe Beged-Dov wrote:

Jeff Sussna wrote:

Given the notion of reification, it would be nice to be able to simply say "property X defined within description Y has the timeframe 1987-1993". As far as I can tell, however, this is impossible, since there is no way to make a statement about a single member of a container (the contained in this case being the Bag of property statements contained by the description).

Taken from the formal grammar section of the spec:

Within propertyElt (production [6.12]), the URI used in a resource attribute identifies (after resolution) the resource that is the object of the statement (i.e., the value of this property). The value of the ID attribute, if specified, is the identifier for the resource that represents the reification of the statement.

Note the second sentence. I don't think that this information is maintained by current parsers but it does allow you to identify the reification of a specific statement in a description.

If it was supported, you could say:

<rdf:Description about="Jimmy">

<rdf:Description about="#44"> 2/3/78 2/2/81

<rdf:Description about="#55"> 2/3/81 2/2/83

Cordially from Corvallis,

Gabe Beged-Dov

Eric Hellman Openly Informatics, Inc. http://www.openly.com/ 21st Century Information Infrastructure

Received on Friday, 31 December 1999 12:34:01 UTC