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> Thomas B. Passin writes:
> > > <?xml version="1.0" encoding="UTF-8"?>
> > > <aircraft>
> > > <elevation>12000</elevation>
> > > </aircraft>
> > Say I want to compare the elevation to the minimum allowed by FAA
> > regs for that location.
> First, a pedantic note (not addressed to Thomas; I just happened to
> pick his message to join the thread) -- the height of the ground, or
> something sitting on the ground, is 'elevation'; the height of an
> airplane, or something else not sitting on the ground, is 'altitude'.
> Now, if I were looking at this in an archive 20 years from now, here
> are the questions I would want to answer:
> - feet or meters?
> - above sea level or above ground level?
> - indicated (pressure) altitude, density altitude, or absolute
Precisely. I have often said that units of measure and other such metadata
are far more important to "data safety" than what people call "strong static
This is why I have long called for a generic constraints system rather than a
monolithic type system for specs such as XPath. Not that generic constraint
annotations will solve all such problems, as you go on to point out. In the
end, program safety and correctness is not something that can be automated by
computer, despite the remarkable claims of strong data typing advocates.
XML has proven invaluable as an undecorated bridge to the ultimately
responsible human, which I argue is its greatest strength. I'm not sure how
or when this goodness came under attack from considerations of "wizards". I
guess, as Simon St.Laurent said, it was probably right after XML took off and
the recalcitrant mainstream programming types realized they had not quite
signed up to what they expected.
Uche Ogbuji Fourthought, Inc.
http://uche.ogbuji.net http://4Suite.org http://fourthought.com
Tour of 4Suite - http://www.xml.com/pub/a/2002/10/16/py-xml.html
Proper XML Output in Python - http://www.xml.com/pub/a/2002/11/13/py-xml.html
RSS for Python - http://www-106.ibm.com/developerworks/webservices/library/ws-p
Debug XSLT on the fly - http://www-106.ibm.com/developerworks/xml/library/x-deb