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Re: ANN: a portable data component -- length

• From: Liam R E Quin <liam@w3.org>
• To: "Costello, Roger L." <costello@mitre.org>
• Date: Sat, 09 Apr 2011 12:00:20 -0400

On Sat, 2011-04-09 at 11:10 -0400, Costello, Roger L. wrote:

> Here is the altitude of an aircraft, expressed in both feet and meters:
> 
>      <altitude>
>          <feet>12000</feet>
>          <meters>3657.6</meters>
>      </altitude>
> 
> It is important that the two length values are consistent:

The right way to mark this up in most cases is to store only one value
and convert as needed.

See Normal Form in database theory: information should never be
duplicated. That way it can't get out of sync.

So my answer is simply, "don't do this."

Instead, e.g.
  <measurement>
    <name>altitude</name>
    <value units="m">3657.6</value>
  </measurement>

(I'd use metric/SI units in a program as they're easier to deal with,
and mixed-based ambiguity like 3 feet 7 inches doesn't occur)

Best,

Liam

-- 
Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
Pictures from old books: http://www.fromoldbooks.org/
Occasional blog: http://www.barefootliam.org/
The barefoot typographer

• Follow-Ups:
  • Re: ANN: a portable data component -- length
    • From: John Cowan <cowan@mercury.ccil.org>
  • Re: ANN: a portable data component -- length
    • From: "Pete Cordell" <petexmldev@codalogic.com>
  • Re: ANN: a portable data component -- length
    • From: Amelia A Lewis <amyzing@talsever.com>
  • RE: ANN: a portable data component -- length
    • From: "Costello, Roger L." <costello@mitre.org>

• References:
  • ANN: a portable data component -- length
    • From: "Costello, Roger L." <costello@mitre.org>