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<Quote>
I am considering returning the result in numerator/denominator form, and
leaving it up to the recipient to do the division (and decide what
precision is suitable), i.e.,
<Length>
<value>
<numerator>33.02</numerator>
<denominator>600</denominator>
</value>
<unit rdf:resource="#Meter"/>
</Length>
</Quote>
Leaving the precision to the recipient may not be desirable,
particularly if the calculation is an "aggregate calculation" that is
carried out by multiple processes each on a different processor (or
different programming language), which may lead a less-than-accurate
precision in the final result.
So an alternative approach is to also specify the required precision for
the calculation result in the XML request:
<Length>
<value precision="15">
<numerator>33.02</numerator>
<denominator>600</denominator>
</value>
<unit rdf:resource="#Meter"/>
</Length>
where "precision" is the number of decimal places for the result. If a
process cannot honor this precision, it could throw an exception.
Kind Regards,
Joe Chiusano
Booz | Allen | Hamilton
"Roger L. Costello" wrote:
>
> Hi Folks,
>
> Suppose that I would like to convert this Length to meters (there are 6
> picas per inch):
>
> <Length>
> <value>13</value>
> <unit rdf:resource="#Pica"/>
> </Length>
>
> Doing the arithmetic:
>
> 13 picas * in/6 picas * 2.54 cm/in * m/100 cm
>
> = 33.02/600 m
>
> = 0.055033333333333333333333333333 m (the "3" repeats infinitely)
>
> The problem is that everyone has different precision requirements. Some
> people would be happy with this as the result:
>
> <Length>
> <value>0.055</value>
> <unit rdf:resource="#Meter"/>
> </Length>
>
> For other people such a roundoff could be catastrophic.
>
> Even if I were to return a result that is as precise as my machine can
> produce,
>
> <Length>
> <value>0.055033333333333333333333333333</value>
> <unit rdf:resource="#Meter"/>
> </Length>
>
> there is still a roundoff that may be unacceptable to some.
>
> I am considering returning the result in numerator/denominator form, and
> leaving it up to the recipient to do the division (and decide what
> precision is suitable), i.e.,
>
> <Length>
> <value>
> <numerator>33.02</numerator>
> <denominator>600</denominator>
> </value>
> <unit rdf:resource="#Meter"/>
> </Length>
>
> What are your thoughts on this? What techniques do people use to avoid
> introducing roundoff errors? /Roger
>
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