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Re: An approach to describing the relationships between units-

• To: "Dare Obasanjo" <dareo@m...>
• Subject: Re: An approach to describing the relationships between units-of-measure
• From: Jeni Tennison <jeni@j...>
• Date: Fri, 25 Jul 2003 10:09:16 +0100
• Cc: "Roger L. Costello" <costello@m...>, xml-dev@l...
• Envelope-to: xml-dev@l...
• In-reply-to: <830178CE7378FC40BC6F1DDADCFDD1D141AB36@R...>
• Organization: Jeni Tennison Consulting Ltd
• References: <830178CE7378FC40BC6F1DDADCFDD1D141AB36@R...>
• Reply-to: Jeni Tennison <jeni@j...>

Hi Dare,

> I wouldn't mind being able to create extension types and extension
> functions in XSLT that could manipulate units of measure as
> intrinsic types the same way strings, booleans and numbers are
> supported (plus dates if you use EXSLT).

Right. That was the kind of thing that the proof-of-concept
implementation from http://www.jenitennison.com/datatypes/ was
supposed to emulate. Obviously it can't hook into the comparison
operators in XPath, but it defines the functions you need.

So you'd define your measurements with:

<datatypes xmlns="http://www.jenitennison.com/datatypes"
           ns="http://www.example.com/datatypes/measurements">

<datatype name="kilometre">
  <parse><ref name="number" /></parse>
</datatype>

<datatype name="mile">
  <parse><ref name="number" /></parse>
</datatype>

<cast from="kilometre" to="mile">
  <value-of select=". div 1.62" />
</cast>

<cast from="mile" to="kilometre">
  <value-of select=". * 1.62" />
</cast>

<define name="number">
  <ref name="digits" />
  <optional><string>.</string><ref name="digits" /></optional>
</define>

<define name="digits">
  <oneOrMore>
    <charGroup><range from="0" to="9" /></charGroup>
  </oneOrMore>
</define>

</datatypes>

Run it through the datatypes.xsl stylesheet and you'd get an XSLT 2.0
stylesheet that defines a bunch of functions for these datatypes.
Import that into your stylesheet, and you can do things like:

  m:compare-miles(m:mile('2000'),
                  m:mile(m:kilometre(River/@length)))

and you'd get -1 if the River is less than 2000 miles long, 1 if the
River is more than 2000 miles long, and 0 if it was exactly 2000 miles
long.

Cheers,

Jeni

---
Jeni Tennison
http://www.jenitennison.com/

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  • Re: An approach to describing the relationships between units-of-measure
    • From: "Roger L. Costello" <costello@m...>

• References:
  • RE: An approach to describing the relationships between units-of-measure
    • From: "Dare Obasanjo" <dareo@m...>

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