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Re: SimpleTypes derived by restriction

From: Curt Arnold <carnold@houston.rr.com>
Date: Wed, 26 Apr 2000 07:33:29 -0500
Message-ID: <001a01bfaf7b$a0d1b780$9344a018@houston.rr.com>
To: <rwaldin@pacbell.net>, <www-xml-schema-comments@w3.org>
My personal preference would be that "looser" facets would be tolerated,
though an ideal schema profiler might tell that you are wasting cycles or
optimize the evaluation.  I don't think that suboptimality is a good reason
to reject a document and the complexity involved in determining the active
constraint set is not justified in my opinion.  While figuring out the
looser constraint is fairly obvious for min/max, what if were trying to
better if one pattern is looser than another (and both could be active).

As a pattern, I know of no programming language that would fail to compile a
conditional like:

if(a > 1 && a > 2 && a < 5 && a <10) {}

It would be a conceptual error for the duration facet to be specified with
two distinct values in a type hierarcy.  You shouldn't be able to derive
from day and stretch the day to 25 hours.  The resulting type (25 hour
periods starting at a particular midnight) doesn't fit into the value space
of 24 hour periods starting at midnight.  I could see making a duplicate
specification of duration in a hierarchy an error, I would not try to
determine if the values of the duration were identical (say if one had said
P1D and another PT3600s)

Multiple period facets can make sense in a hierarchy make sense.  You could
create a derived type from time with a period of 48 hours that represented a
particular time of day every other day.  I can't see anything a schema
validation can do with the period facet.  It seems like a piece of
information only the application uses (if it wants) to determine the meaning
of the type.
Received on Wednesday, 26 April 2000 08:43:54 UTC

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