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   Re: [xml-dev] W3C Schema: Resistance is Futile, says Don Box

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Michael Kay wrote:

> So what's the accurate value, remembering that XML Schema and ISO 8601
> both use a proleptic Gregorian calendar, and that the ISO 8601 calendar
> includes a year 0 while the XML Schema version does not?

Your reminders above are useful for one who chooses to employ a gDate
process for instantiating a date from the attribute value "-43-03-13". I
see other infelicities with using that particular form of markup if the
instance is to be processed by widely useful general purpose tools, but
that is not the primary issue here. The element content itself (the ides of
March, 710 A.U.C.) if instantiated as a date by an accurate application of
the AUC process as redefined by Caesar himself must yield a result of the
fifteenth day of the third month of the 710th year. That is the point of
units as a component of the lexical content which is to be instantiated
with some particular semantics. If the units are to be given the semantic
expression generally expected, then those semantics will be elaborated
through an algorithmic process--a reckoning--which yields semantics
predicated on the chosen units. Converting inches to centimeters with a
coefficient of 2.54 is such a process. Performing the resolution of an AUC
date as prescribed by Caesar is another. Resolving a date from lexical
content by the operation of a gDate algorithm is a different process.

My original point with John is that a date which claims to carry the
semantics of AUC units should resolve to the result which the AUC process,
as defined, yields from the given lexical input. The AUC resolution
algorithm is a definition of process, not of nominal identity, just as is
the definition of inches in terms of centimeters. The deeper point is that
the element content, and separately the attribute value, in this instance
are merely syntactic constructs as given. Resolved as a date on one simple
reading of  its own terms (i.e., AUC) the element content yields a result
which is unquestionably the 15th of March. Resolved as a date through the
execution of a gDate process the attribute value yields the 13th. The
markup, as given, might be reasonably interpreted (an elaboration of
specific semantics through process) to assert that these dates are the
same. From a third party point of view (John's time travel argument) they
can be so understood. But on the particular terms of each process, there
are separate and different results. A process which yields any other date
than the 15th in this instance cannot legitimately be considered an AUC
process, or more exactly a process elaborating AUC semantics. The element
content includes AUC units. We cannot claim to instantiate that content on
those units if we reach any other result than the 15th.

I apologize if this seems like nitpicking or if my point appears nearly
invisible. It is not. Redoing two centuries of scholarship in philology
(and reversing the implicit semantic understandings of twenty previous
centuries) has amply demonstrated that a carefully articulated progress
from the lexical to the objectified is necessary once we understand the
difference between a text and its instantiated semantic elaborations. I am
pushing as best I can to get the practice of XML to that point as
completely and swiftly as possible. I try not to be too pushy about it, and
will not take it amiss if I am told to slow down or to revisit arguments,
but I know where I am going and I intend to get there with, I hope, as
great a number as can be persuaded that this is a worthwhile exercise.


Walter Perry


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