Asynch: Conversions via XSL #2

[martin.weber@nist.gov]

Some more explanations / random notes:

The example.zip contains all the stuff necessary to test xsl based
conversions between units based on UnitsML. The demo should actually
perform conversions instead of just outputting the formula to be applied,
and thus a numeric value that is related to a unit is required. Given that
in UnitsML itself there is no specific place for a numeric value, I have
"invented" the "NVUnitsML" (NV=Numerical Value) which includes a subset of
UnitsML (the UnitSet) and a values container which can contain value
containers which then can contain (lists of) numerical values. An
attribute (unitIDREF) establishes the link to the unit in question.

The stylesheet (convertToTargetUnitSystem.xsl) builds on the NVUnitsML
(i.e. it looks for the numerical values where nvunitsml would put them
although it should be trivial to adopt the stylesheet for any other
language including unitsml). It extracts the formulae necessary to convert
from one unit to another, and applies this to the numerical values. The
result document then contains an updated unit reference as well as updated
numerical values.

In UnitsML (for the linear float 64 conversion) only formula "from"
another unit are stored, not "to" another unit. These are trivial to
create though, which also is what the stylesheet is doing. There could be
done even more when multiple conversions (e.g. seconds -> minutes -> hours
-> days) are condensed (i.e. seconds -> minutes; seconds -> hours; seconds
-> days), which is on cTTUS.xsl's TODO.

The USCDL comes into play only to describe details of the conversion, i.e.
the "how exactly" and "what to". I have a little presentation somewhere of
how to use it, but it's not that important. I do not expect an end-user to
create a USCD file; if, at all, this is going to be used 1:1, then I
expect a web developer or someone like that to create a few files for
"pre-defined, supported conversions" on their site/files/data. The schema
should be adequately documented, and it's short.

When looking at the example files, you should have a look at the values
sections of each (time-nv.xml, Example1.xml, Example2.xml) and look at the
units the values are in.

Hmm, I think that's all I wanted to add for now..

-Martin