I found the NPR story ... search for
"Goedel" on npr.org and you'll get one hit. ("Gödel" doesn't get any matches,
sigh ...). There's a Real Audio file containing the segment.
The
mathematician is Keith Devlin, the "math guy". He says, and I freely
paraphrase ... Goedel is hovering behind the semantic web ... to do something
like what Tim Berners-Lee is trying to do, you have to code in axioms and rules
of deduction. When you do that, there are things that are true that users
want to know that can't be deduced from the axioms. The Semantic Web will fail
to do some of the things that the users want it to do, and there is no escape
from this within the rules of logic.
Other fun facts about Gödel
(courtesy Dr. Devlin)... he had to be restrained from explaining the logical
inconsistencies in the US Constitution at the ceremony naturalizing him as a US
citizen ... and starved to death because he feared that someone was poisoning
him, which (quite logically!) led him to avoid food.
Based on my
20-year-old recollection of "Gödel, Escher, Bach" and "Gödel's Proof", and
discussions thereof in a long-ago AI course ... I'd guess that Gödel's theorem
would suggest that there are "truths" that a Google-like search engine (that
gives credibility to assertions that are widely quoted) could find that a
Semantic Web logical inference engine (that gives credibility to assertions that
can be proven) couldn't find. Whethere there are *interesting* truths that
would suffer this fate is another matter ...
The bigger problem with the
SW, as many have noted, is that Gödel will never hava a chance to screw up the
works, because he only talks about the incompleteness of CONSISTENT sets of
axioms. Getting consistency in the SW's vast network of RDF metadata will
be a monumental problem, and ANYTHING can be proven in with an inconsistent set
of axioms (as my poor remaining neurons dimly recall my higher
education).
So, at best the SW will have to employ some heuristics for
finding useful axioms to feed into a logical inference engine. Whether
this is worth the cost is another matter.
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