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Fwd: [xml-dev] ANN: a portable data component -- length

Normal form isn't the only way to express data. It works for some
scenarios but decidely not for others; take analytical databases, data
marts, data warehouses, etc. For ages in the UK we had to have the
price of loose fruit and vegetables on our shop shelves expressed in
both price per imperial and price per metric weight. We still have
shoes and clothes sold in UK and EU sizes. We don't give people one
price and say "go work the other price out" or one size and say "go
work out the other size; here is the conversion factor"... So we often
produce price lists, I expect in XML, with multiple prices in mutliple
currencies and we design database table deliberately with redundant
information so that there is no need for extra time spent
dereferencing information held in separate tables. I think Roger's
examples hold well.

On 09/04/2011, Liam R E Quin <liam@w3.org> wrote:
> 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
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Stephen D Green

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