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Re: Re: What are units-of-measure? e.g., what's a "kilometer"?

• To: "Roger L. Costello" <costello@m...>, xml-dev@l...
• Subject: Re: Re: What are units-of-measure? e.g., what's a "kilometer"?
• From: Linda Grimaldi <grimlinda@e...>
• Date: Thu, 17 Jul 2003 14:02:13 -0600 (MDT)

This is an advantage.  But effectively, you have introduced a new requirement- not just to describe the length of the river, but to allow for conversion.  The conversion aspect introduces an important differentiator- kilometer itself can usefully be assigned properties which means it has to be promoted from a simple value.

Linda
-------Original Message-------
From: "Roger L. Costello" <costello@m...>
Sent: 07/17/03 01:45 PM
To: xml-dev@l...
Subject: Re:  What are units-of-measure? e.g., what's a "kilometer"?

> 
> Alaric B Snell wrote:

> Roger L. Costello wrote:
>
> > This is quite a radical approach.  I am surprised that there
> > aren't more comments, since the "conventional wisdom" is
> > not to treat kilometer as a property/relation/function, but rather
> > to treat it as the value of a property, e.g.,
> >
> >   <River id="Yangtze">
> >        <length unit="kilometer">6300</length>
> >   </River>
>
> The advantage of "<kilometres>6300</kilometres>" as opposed to <length
> unit="kilometre"> is in modularity of type definition.

I believe that the key advantage of this approach:

   <River id="Yangtze">
        <length>
            <kilometer>6300</kilometer>
        </length>
   </River>

is the capability to state the relationship to a length value expressed
using a different unit-of-measure, e.g.,

   <River id="Yangtze">
        <length>
            <mile>3914</mile>
        </length>
   </River>

Namely, the relationship is:

     "a kilometer property is equal to a mile property  times 1.62".

A very compelling example of this capability is to determine that
two documents, which express a location using different
units-of-measure, are referring to the same location, e.g.,

<Map id="M1">
    <location>
        <cartesian-coordinate>
                ...
        </cartesian-coordinate>
    </location>
</Map>

<Map id="M21">
    <location>
        <polar-coordinate>
                ...
        </polar-coordinate>
    </location>
</Map>

Namely, the relationship is:

    "a cartesian-coordinate property is equal to a polar-coordinate
     property ...".  (If someone can complete this sentence I would be
very
     interested.  I have long forgotten how to convert coordinate
systems.)

I don't believe that with the other approach:

   <River id="Yangtze">
        <length units="kilometers">6300</length>
   </River>

it would be possible to make such relationship statements, and that's a
show-stopping disadvantage.

Thoughts?  /Roger





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