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Re: Re: An approach to describing the relationships between un

• To: "Roger L. Costello" <costello@m...>
• Subject: Re: Re: An approach to describing the relationships between units-of-measure
• From: John Cowan <cowan@m...>
• Date: Wed, 23 Jul 2003 07:58:16 -0400
• Cc: xml-dev@l...
• In-reply-to: <3F1E7219.C68E530F@m...>
• References: <3F1D1A9C.C04EA743@m...> <3F1E7219.C68E530F@m...>
• User-agent: Mutt/1.3.28i

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@r...
    Abstract schemata                           http://www.reutershealth.com
    XPointer errata                             http://www.ccil.org/~cowan
Infoset Unicode BOM                                 --Richard Tobin

• References:
  • Re: An approach to describing the relationships between units-of-measure
    • From: "Roger L. Costello" <costello@m...>
  • Re: Re: An approach to describing the relationships between units-of-measure
    • From: "Roger L. Costello" <costello@m...>

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