Just a little off-topic "cri de coeur" about the naming of relations: (01)
[Chris Menzel said]
>
> But why? "creator" in that example from the RDF documentation is
> simply
> short for "is the creator of", which corresponds almost exactly to the
> definition of "predicate" that you yourself provided.
> (02)
Actually, in that document it is short for "has creator", which has the
opposite polarity from "is the creator of".
This is an extremely easy-to-make misinterpretation when simple nouns are
used to name relations: the polarity could logically be defined either way,
and different people use it in different ways. (03)
I really, really wish people would just stop using simple nouns to express
relations, and always use a verbal form like "isTheCreatorOf" or
"hasCreator" or "is_the_mother_of" because when a simple noun is used there
is time wasted trying to remember or recheck just what the intended polarity
was, and a significant probability that it will be used incorrectly. That
sort of usage was fine when logicians were writing papers with one or two
example relations and one had lots of examples of that relation to burn its
polarity into one's brain by the end of the paper. With ontologies having
hundreds or thousands of relations and people using the same relation name
with different polarities, we are wasting time and risking error on a
completely unnecessary ambiguous convention. (04)
For clarity, in the examples I use to explain things, I use a simple
modification of the KIF format, using curly braces to invert the order of
the first two elements, so that
(istheMotherOf Mary Sam) appears as:
{Mary istheMotherOf Sam}.
When multiple arity relations are allowed, defined particle words
associated with relations can also help, as in
{NewJersey isBetween NewYork and Pennsylvania}.
Wherever the usual KIF order makes linguistic sense, it can be retained,
as in:
(subtracting ?x from 15 gives 10). (05)
This should be easier to understand for those who speak an SVO language like
English. Other languages can define their own order or delimiters. It
would save time and make it easier to read discussions of complex axioms.
Converting the braced format back to normal KIF can be done with a trivial
utility. One doesn't actually have to use this notation, but knowing that
the inversion of the first two elements creates the English-like SVO
sentence will make the polarity clear, if the relations are named verbally. (06)
I can't quite understand the persistence of the use of simple nouns as
relation names. It seems to be a holdover from a time when logic was done
on very small sets of example relations. (07)
Pat (08)
Patrick Cassidy
MICRA, Inc.
908-561-3416
cell: 908-565-4053
cassidy@xxxxxxxxx (09)
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