[dsdl-discuss] Re: Numbers and units

Hi Rick,

Rick Jelliffe wrote:
> From: "Eric van der Vlist" <vdv@dyomedea.com>
>
>
>>Thinking more about Rick's
>>
>> <dsdl:number unit="dollars_per_cubic_litre">15</dsdl:number>
>>
>>I assume that it's either "dollars_per_litre" or
>>"dollars_per_cubic_decimeter" that this doesn't carry the fact that
>>"dollars_per_cubic_decimeter" is the unit "dollar/dm**3".
>
>
> Yes, and that is a feature, not a bug. It is a rational number with a
> named unit, just is the minimum for representing the widest variety
> of numbers.

The tradeoff between "minimum" and "widest" is very subjective IMO!

Other "minimums for representing the widest variety of numbers" include:

- Using decimal numbers rather than rational numbers (this is "more
minimal" but "less wide")...
- Using a more formal description of numbers and MathML seems to be a
plausible alternative.

> My approach is based on the criteria that we need to support the
> kinds of attribute values (and data values) actually found in real
> markup languages in the publishing area. There is no requirement
> from that for expressing the semantics of units, merely for simple
> conversions (such as from inches to centimetre) AFAIK.

Might be, OTH even so, a formal description of the relations between the
units would be computable by the validators which would be able for
instance to deduce the relation between square inches and square
millimeters from the relationc between inches and centimers and the
relation between centimeters and millimeters.

What I don't like about using attributes for the units is that it's not
extensible and that you can't "qualify" the unit.

>>If we think that the "fractional number/ unit" is the way to go, I think
>>that units should be given a better treatment :-).
>>
>>Similarly, I think that we should question the fact that fractional
>>numbers are the "universal solution" (what about representing the number
>>"pi" or square root of 2 ?)?
>
>
>
> My approach is based on the criteria that we need to support the
> kinds of attribute values (and data values) actually found in real
> markup languages in the publishing area. There is no requirement
> from that for a "universal solution" AFAIK.

I have very mixed feelings about this sort of arguments :-)

On one hand, I agree that we shouldn't try to solve issues which don't
exist in the real world, OTH it's by using this kind of arguments again
and again that W3C has produced such a mess with W3C XML Schema.

If we can define a mechanism to better define what "numbers" and "units"
are, if this mechanism doesn't add that much complexity and if it's
based on existing technologies I think that it's something we should try
to look at especially when we are in "brainstorming mode" like we are now!

Eric

>>If we accept the notion of a transformation between the parsed and
>>lexical spaces, wouldn't MathML be a good target as lexical space?
>
>
> See above.
>
> Cheers
> Rick

-- 
See you in San Diego.
                                http://conferences.oreillynet.com/os2002/
------------------------------------------------------------------------
Eric van der Vlist       http://xmlfr.org            http://dyomedea.com
http://xsltunit.org      http://4xt.org           http://examplotron.org
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