Re: Well Behaved RDF - Taming Blank Nodes, etc.

On 12/13/2012 4:48 AM, Bernard Vatant wrote:
> I'm 100% with Pat here in the defence of blank nodes, as ever [1] The
> more I'm using RDF daily, the more I love them, and seems to me you
> miss a lot of RDF expressivity by wanting everything to be uniquely
> identified by a URI Just another example : "John met a girl yesterday
> in a cafe". Are you going to coin a URI for those ill-identified
> girl, cafe, and event? Certainly not. But you want to record this
> information in John's bio because you guess it's likely to be of some
> importance later in his life, even if so far you don't know more
> about it.

Nicely stated.  More generally, there are two different ways to describe
or identify something.  One uses a (probably arbitrary) identifier, such
as a URI or a person's name.  The other uses a bundle of properties. For
example, it has been reported that around 87% of the US population can
be identified by the combination of {5-digit ZIP code, gender, date of
birth} (see
http://dataprivacylab.org/projects/identifiability/paper1.pdf).  Of
course, we usually don't even need to make a fully unique identification
for a bundle of properties to be very useful, as Bernard illustrates.

Using a bnode corresponds to using a bundle of properties to describe
the subject.  If we don't allow the use of bnodes, we eliminate one of
the two basic ways of describing something.  That's a loss of the
expressiveness that Bernard talks about above. Why would we want to
limit ourselves so severely? I wouldn't.