Hi Evan --
Some late Friday night thoughts. You have heard some of these before,
but hopefully they may be of interest to the list folks, and it would
be good to get your comments if you have time.
You wrote....
As I understand it,
what is important to you [Patrick] and to Ontolog is the expressivity of FOL. OWL
doesn't have that-- now or probably ever. The SW may, but not anytime soon.
There are actually many related practical concerns hiding under the
expressivity umbrella:
1. If we make things very expressive, the known inference techniques
are either NP-complete or uncomputable.
2. People seem to have a hard time specifying all but the simplest
tasks error-free in full FOL. Long chains of quantifiers are
particularly hard to write and read correctly. Diagramatic techniques
help with small examples, but we get lost in the spaghetti or in
zooming around on larger ones.
3. Even if a spec in some version of logic is correct, it may be hard
to follow the inferences that it makes, specially if they are based in
a machine-oriented notation.
4. The above points will likely place automatic inferences over the
future semantic web beyond the comprehension and control of computer
scientists, let alone business folks.
So, do we throw out RDF, OWL and logic, and start over?
Of course not. I'd argue that, instead, we can keep much of the
progress so far, but that:
1. the level of expressivity has to be chosen very carefully, based on
practical considerations and use cases
2. we should be mainly content with double negations in place of
quantifiers -- they are the lesser of the two human factors evils
3. we must tie machine oriented notations computationally to human
oriented notations
4. explanations, as close to English as we can make them, are going to
be essential if we are to have any idea what the future semantic web is
doing for (or against) us.
Her's a little example of a reasoning chain to try to illustrate the
above.
Paper is related by fact#:title to
An Overview of RDF Query Languages
count eg-name : eg-name is an
author of An Overview of RDF Query Languages = 4
----------------------------------------------------------------------------------------------------------------------
the publication An Overview of RDF
Query Languages has 4 author(s)
Andreas Eberhart is an author of An
Overview of RDF Query Languages
Jeen Broekstra is an author of An
Overview of RDF Query Languages
Peter Haase is an author of An
Overview of RDF Query Languages
Raphael Volz is an author of An
Overview of RDF Query Languages
-------------------------------------------------------------------------------------------
count eg-name : eg-name is an
author of An Overview of RDF Query Languages = 4
Paper is related by fact#:title to
An Overview of RDF Query Languages
Paper is related by fact#:author to
__Description1
__Description1 is related by rdf:_2
to aeb
aeb is related by fact#:name to
Andreas Eberhart
-------------------------------------------------------------------------------------------
Andreas Eberhart is an author of An
Overview of RDF Query Languages
Paper is related by fact#:title to
An Overview of RDF Query Languages
Paper is related by fact#:author to
__Description1
__Description1 is related by rdf:_1
to http://www.cs.vu.nl/~jbroeks/
http://www.cs.vu.nl/~jbroeks/ is
related by fact#:name to Jeen Broekstra
-------------------------------------------------------------------------------------------
Jeen Broekstra is an author of An
Overview of RDF Query Languages
...and so on...
(Apologies if the format of the above explanation looks bad in email.
You can also see it hypertexted in a browser by running the example
RDFQueryLangComparison1 at the link below.)
Does this make sense? Cheers, Adrian Walker
--
Internet Business Logic -- online at www.reengineeringllc.com
Reengineering LLC, PO Box 1412, Bristol, CT 06011-1412, USA
Phone 860 583 9677 Mobile 860 830 2085 Fax 860 314 1029
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