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Roger L. Costello scripsit:
> Recap: Don't state the relationship between different UOMs!
> Instead, state the relationship between a UOM and its
> reference standard.
Yes, indeed.
> canonical(mile) = $value * 1620
The exact conversion is 0.0254 (meters per inch) * 12 (inches per foot) *
5280 (feet per mile), or 1609.344 meters per mile. You want to use
rational decimal arithmetic rather than binary floating point when
doing this sort of work.
> <River id="Yangtze">
> <length>
> <meter>6340680</meter>
> </length>
> </River>
Rather <meter>6298972.416</meter>
> Question: what is the canonical form of compound UOMs, such as:
> - m**2 (meters squared)
> - m/sec (meters per second)
> - m/sec**2 (meters per second squared)
Such a form can always be reduced to a fraction, with a list of numerator
units and denominator units. If we sort the units in alphabetical order,
then we get a canonical form for it. For example, the canonical
form of volts is "kilogram meter meter / ampere second second second".
Exactly how to represent this in XML I leave up to you.
--
XQuery Blueberry DOM John Cowan
Entity parser dot-com jcowan@reutershealth.com
Abstract schemata http://www.reutershealth.com
XPointer errata http://www.ccil.org/~cowan
Infoset Unicode BOM --Richard Tobin
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