John F. Sowa wrote:
> The folks who developed the Opera browser searched the WWW to
> gather statistics about the percentage of web sites that adhere
> to the W3C standards for HTML and XML. They found that only 4.13%
> of the sites are standards compliant. Even more discouraging that
> of those sites that have a logo claiming to comply with W3C
> standards, only 50% were actually compliant. See
>
> http://arstechnica.com/news.ars/post/20081015-opera-study-only-4-13-of-the-
> web-is-standards-compliant.html
>
> This should be a cautionary point for anybody who is proposing
> to develop or use standards for ontology. Since a single
> discrepancy can cause a theorem prover to collapse into
> contradiction, it is important to design systems to expect
> discrepancies. (01)
With all due respect, John, I think you are comparing apples and oranges. (02)
First, we have to recognize that three factors contribute to a lot of
invalid HTML:
- the design of the browsers, and toolkits that enable use of certain
browser features by using not-quite-standard constructs
- the popularity of bells-and-whistles plug-ins (java, flash, etc.) to
empower webpage "content delivery" and their associated advertisements
- the size of the webpage development market, and the consequent
number of webpage mechanics, 20% of whom are of better than average
competence.
In so many words, if your mechanic's concept of a validity test is that
it works with the version of IE and Java and Flash on his system, you
can expect a low level of compliance. (03)
I have no doubt that if and when we start seeing significant numbers of
RDF and OWL ontologies, or even document annotations, on the Web, we
will start seeing significant numbers of _invalid_ RDF and OWL
documents. But in that community, because of its size and nature (small
market, high competence), much more attention will be paid to "doing the
thing right". I would bet that 80% of current and future RDF and OWL
documents will be valid. Some that are technically invalid will be
accepted by parsers anyway, and probably interpreted as intended; others
will be rejected by the parsers and never participate in any reasoning
activity. (04)
But that is not the comparison John was making. What will make or break
automated reasoning over multiple information sources is, to paraphrase
John's point, how many of the valid ontologies "do the right thing".
How many of them convey 'correct' or at least 'consistent' information?
The Web in general is the source of as much misinformation as useful
information, and we have no reason to suppose that "ontology-engineered"
information will be any more correct. Further, my experience as a
modeler tells me that most people generalize incorrectly quite often.
We are perforce all guilty of false induction from time to time, based
on limited knowledge and experience, and our ontologies will reflect
that. (This is just yet another phrasing of Pat Hayes's "Horatio
principle".) (05)
The big issue for the proponents of "ontology repositories" is not
whether the proffered ontologies are valid OWL/RDF/CLIF. It is: How do
you decide whether a proffered ontology is "good"? And how do you
resolve discrepancies when trying to enrich your overall knowledge base?
Is the new information wrong? or the old information? Or does the new
ontology just reflect a viewpoint for which the reconciliation with
other viewpoints is not yet fully developed in the community? (All of
these issues came up in the last summit.) (06)
-Ed (07)
--
Edward J. Barkmeyer Email: edbark@xxxxxxxx
National Institute of Standards & Technology
Manufacturing Systems Integration Division
100 Bureau Drive, Stop 8263 Tel: +1 301-975-3528
Gaithersburg, MD 20899-8263 FAX: +1 301-975-4694 (08)
"The opinions expressed above do not reflect consensus of NIST,
and have not been reviewed by any Government authority." (09)
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