[foaf-dev] (static) functional properties for distinguishing people?
danbri at danbri.org
Sun Mar 1 11:19:04 CET 2009
Apart from one's natural date of birth, what other properties do you
folk consider to be "functional" (and statically so)? I'm asking with
regard to telling when two descriptions are of different people.
In RDF/OWL a property is functional if, for some particular thing, there
is at most one true value for any specified property. Since RDF and OWL
don't take time or context into account, this leaves a grey area around
properties such as "age". I don't want to get into that modeling issue
right now, but I am interested to look for plausible properties that can
be used when comparing people descriptions, so we can say "if these two
descriptions are both true, then they must be descriptions of two
Historically we have focussed more on the complementary situation:
figuring out when two descriptions are about the self-same thing (in
FOAF, typically Person). This is useful, but we've neglected the need to
If I'm given:
a.rdf: <Person><homepage rdf:resource="http://danbri.org"/></Person>
... nothing in RDF's logic prevents those from being about two different
people. But they might also be descriptions of the same person.
similarly, even if a.rdf and b.rdf used URIs for people, RDF's logic
still allows that they could just two identifiers for the same person.
This makes it difficult to go from a count of person descriptions, to
counts related to the number of actual people mentioned.
With these, if x-dob is defined carefully, and we have conventions to
avoid syntactic variation, impact of xml language tags, "official
birthdays" (UK's Queen, etc etc), missing year field, use of 0000 for
"don't knows", and other cornercases, ... it is conceivable that we
could conclude from differing x-dob fields that we are dealing with
There are of course privacy issues with "date of birth" fields (its use
in banking security questions, for example).
Are there other general (not country-specific) properties of people which:
a) never change throughout (or after) their life
b) have simple lexical representation such that computing a comparision
c) have no security, privacy concerns beyond those intrinsic to being a
way of distinguishing and describing people (ie. are not valuable secrets).
I can't think of any right now, and suspect the mix of technical and
social considerations involved make this approach eternally infeasible.
Just wanted to check I wasn't blanking out and missing something
obvious. I assume we'll get by with hacks and heuristics rather than
pure logical guarantees. Sometimes the data world is messy for good
Thanks for any thoughts,
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