I agree that a strong semantic is
necessary to avoid misinterpretation of units data, however what we presently
have falls short of capturing all the required units. That said, is there a
reason we cannot extend the regular expression for the ‘units’
attribute (extract from Common.xsd below) to encompass the units that will be
encountered in practice? Adding a free-text modifier attribute would make
sense if the possible patterns for a units Type could not be presently defined
and bounded.
Best regards,
Kevin Coggins
From Common.xsd for reference:
- <xs:simpleType name="Unit">
- <xs:annotation>
<xs:documentation>Used for ATML
schema elements that contain the unit for a numerical value (i.e.
‘volts’, ‘ohms’, ‘MHz’, etc.).</xs:documentation>
</xs:annotation>
- <xs:restriction
base="xs:string">
<xs:pattern
value="((y|z|a|f|p|n|µ|u|m|c|d|h|k|M|G|T|P|E|Z|Y)?(F|S|C|A|V|J|eV|T|N|Hz|lx|H|m|in|ft|mi|nmi|lm|cd|Wb|g|rad|deg|°|W|BW|Bm|Pa|bar|B(\(\d*m?W\))?|%|pc|Ohm|sr|K|degC|°C|degF|°F|s|min|h|L|mol)\d*((·|\.|/)(y|z|a|f|p|n|µ|u|m|c|d|h|k|M|G|T|P|E|Z|Y)?(F|S|C|A|V|J|eV|T|N|Hz|lx|H|m|in|ft|mi|nmi|lm|cd|Wb|g|rad|deg|°|W|BW|Bm|Pa|bar|B|%|pc|Ohm|sr|K|degC|°C|degF|°F|s|min|h|L|mol)\d*)*)?" />
</xs:restriction>
</xs:simpleType>
From:
owner-stds-scc20-atml@ieee.org [mailto:owner-stds-scc20-atml@ieee.org] On Behalf Of Wilmering, Timothy J
Sent: Wednesday, December 14, 2005
8:21 AM
To: Ralph, John (Mission Systems);
stds-scc20-atml@listserv.ieee.org
Subject: RE: Common schema units
of measure
This
is one of the places where a strong semantic is enforced to good effect.
Misinterpretation of units data would obviously result in erroneous stimulus,
measurements, etc, and at worst case could be catastrophic. Relying on
"best judgment" is never a good idea when thinking of general
applications over the long haul - well-intended judgment could also be horribly
mistaken. I *strongly* urge you not to weaken this very important semantic
validation.
Case
in point:
The
Mars Climate Observer crashed into the surface of Mars, a victim not of a
technical problems, but of a semantic misunderstanding concerning the units of
measure used to calculate the thrust.
'nuff
said.
Tim
_________________________________
Timothy J. Wilmering
'314.234.6781
-<mailto:timothy.j.wilmering@boeing.com>
From: Ralph,
John (Mission Systems) [mailto:John.Ralph@NGC.COM]
Sent: Wednesday, December 14, 2005
8:16 AM
To:
stds-scc20-atml@listserv.ieee.org
Subject: Common schema units of
measure
As some of you may be aware, there is a 'units' attribute
applied to several elements in the Common schema. A regular expression has been
defined to limit the contents to standard SI and some English units of measure.
Late breaking input has shown that this is too stringent, and
doesn't permit "extended" units such as "V rms" or "V
peak-to-peak", etc. Accordingly, two suggestions have been put forth:
1. Drop the regular expression validation on 'units'
2. Add a free-text "modifier" attribute that applies
to 'units'
In option 1, we would then be dependent on the "good
engineering judgement" of schema users to ensure that unusable or
non-standard units of measure are not introduced.
Option 2 would still impose a regexp validation on the 'units'
attribute, and schema users could put any sort of "modifier" they
needed in the 'unitQualifier' attribute. This has the advantage of at least
SOME level of standardization on units of measure.
This needs to be resolved ASAP, as there are participants
currently implementing and they need a "locked down" schema to work
against.
Thoughts?
John
Ralph