- From: Jim Hendler <hendler@cs.rpi.edu>
- Date: Mon, 26 Nov 2007 12:00:52 -0500
- To: "OWL Working Group WG <public-owl-wg@w3.org>" <public-owl-wg@w3.org>
- Message-Id: <A80EEDE0-78C6-4B64-AE53-C5FECF636142@cs.rpi.edu>
I have taken a long time to answer this question, because I had to
count to 10, and then count to 10 again -- I've now reached somewhere
around 10^^6 and am calm enough for an answer - in fact, several:
ANSWER 1: Someone like me wants a reference manual
OK, Bijan argued that since users will mainly use OWL through
tools, they didn't really need to know most of this. Ok, maybe, but
suppose I got to a SWOOP or Protege for OWL1.1 and create a new
property - I get a menu asking me what kind of property it is. One
of my choices is
owl11:irreflexive property.
hmm, I vaguely remember that reflexive and irreflexive were things I
learned about in college math over 30 years ago, so I had better
check the documentation to see if this is what I want. The overview
gives me something like an example
IrreflexiveObjectProperty(husbandOf)
which confuses me a bit because the term my editor shows me is
"irreflexiveProperty" but even assuming these are the same, this one
example doesn't tell me anything. (and the example for Reflexive is
"knows" which happens not to be a reflexive property in many systems,
but I digress)
In the structural document all I can discover is that it is
syntactically legal in some syntax I don't use (remember, I'm doing
this through an editor as Bijan argued, so I don't see any syntax
except what is displayed by the editor). So that doesn't help.
Gritting my teeth, I go to the model-theoretic semantic (most users
by now would have simply decided not to use it, but I'm a bit
stubborn). I find there (in a table, which means my browsers search
didn't find it so I had to scroll through the whole document) that
x ∈ ΔI implies ( x , x ) is not in RIpo (sorry for the
syntax, but that's how it comes out when I cut and paste to mail it
to someone who might be able to answer the question).
Well maybe from that I could figure out the answer if I was
slightly less stupid, but I'm still confused, I check the RDF
mapping, but it also only gives me syntax.
So now I go out on the Web and find some definition of irreflexive
and I finally get it -- time wasted because there was no manual - on
the order of 30-45 min. And that's for one of the easy one (try
ObjectExistsSelf where { x | ( x, x ) ∈ RIpo } is the only
explanation)
There's a lot of functions in this thing named after math I'm not
familiar with and defined only in a logic I'm not familiar with. My
conclusion - to hell with OWL, make up my own stuff in RDFS.
ANSWER 2: My students - a guide
Ok, I give a lecture in class, I give some examples, I assign my
students to go write an ontology. Oops. every one of them has the
problem above in spades - not only don't they understand this stuff,
but they don't have my experience with OWL. So they puzzle out what
they think things mean, but they want to try it -- boy, would be a
lot easier if they had some examples they could cut and paste into
something (validator, etc.) so they could not only figure out the
meaning, but also puzzle out the syntax.
ANSWER 3: People considering use of OWL for a project - better overview
Dean Allemang and I are in the finishing stages of a book about how
to use OWL 1.0 -- we were motivated because in teaching professionals
interested in using the Semantic Web (usually the decision makers for
their companies or people who report to the decision makers) we found
that they had read the overview, decided they liked the idea of OWL
and wanted to take a course before they dove in. (They then wanted
something that emphasized the stuff we had in the course, so we wrote
the book). We've been teaching the course for several years now, we
are finally getting the book done, but again, these users have
usually read the overview - so the book alone wouldn't have been
enough for them - they needed something to whet their appetites.
In general these people are business people working for companies
or for the government. They are well-educated professionals (college
grads in general, usually some sort of professional masters,
occasional PhD in engineering or some non-CS field) with a high level
of domain knowledge, and usually some programming background, but
they've rarely taken a logic course.
These users have a lot of demands on their time, without a simple
thing to look at and decide they want to learn more, they usually end
up doing something else. A number of them have Shelley Powers' RDF
book and are pretty much convinced by RDF/RDFS but are a bit
skeptical of OWL (and I fear will be much more so of OWL 1.1 because
the more complex a language, the higher the learning curve, and many
of these folks are learning-curve adverse because of the time it takes)
So there's my top 3. I've left out Web Application developers
because in my experience they will mainly ignore all our documents
and just use the pieces of the RDF (OWL Full) vocabulary that make
sense to them, and ignore the rest - however, if there is a
reference, they do tend to make sure that what they think is being
defined is right - i.e. they would like to make sure the operational
semantics of what they develop matches as close as possible to the
reference manual.
-JH
p.s. I note that the OWL Reference and Overview are the two highest
ranked in Google and interestingly the S&AS document, despite being
normative, is lower in Google rank than any of the others except for
Use cases, with which it is tied... I know Google rank is variable
and also not a definitive argument for anything, but it does indicate
more people linking to the user facing documents over the developer-
oriented one. Doesn't deny the importance of that document, just
stresses the importance of the others to uptake...
"If we knew what we were doing, it wouldn't be called research, would
it?." - Albert Einstein
Prof James Hendler http://www.cs.rpi.edu/~hendler
Tetherless World Constellation Chair
Computer Science Dept
Rensselaer Polytechnic Institute, Troy NY 12180
Received on Monday, 26 November 2007 17:01:30 UTC