prior knowledge of scale for standard units

[Matt Jones]

Tim,

So, are you saying that "unit" implies measurement scale?  That is 
probably true, but it would be much harder to nest measurement scale in 
unit as not all measurement scales have units, and there are infinite 
numbers of units.  An application that digests the units and thereby can 
suggest (or even automatically fill in) a measurement scale would make 
the whole thing more usable.  But I think that is an application issue 
more than an EML one.  I don't see a need for any changes to the schemas 
to enable applications to guide users based on units.

Can you outline a bit more concretely what you were proposing?

BTW, I found that I fully agreed with your treatise on datetime as a 
coordinate system.  You said "Arbitrariness is handled by projecting the 
points onto an evenly divided, "true" interval scale, such as a string 
of named seconds starting in 1970."  I fully fully agree that this is 
the case here. Datetimes are ordinals (given any two datetime values, 
they always have a pre-determined ordering).  Datetimes can be projected 
onto an interval scale such as seconds since 1970.  The fact that most 
scientists consider datetimes as interval values is more from pragmatism 
than theoretical correctness.  We could move the datetime format string 
out of unit and into ordinal if people prefer.  THis would be more 
technically correct, would also eliminate our problem with the precision 
field for datetime values, and would remove the format string from 
UnitType so it would no longer show up under interval (and ratio, which 
is good).  It would introduce a need for dateTimeDomain in ordinal, 
which would be ok too.

Does anyone have a preference about whether this should in fact be in 
ordinal or in interval?

Matt

Tim Bergsma wrote:
> Matt,
> 
> We know already the measurementScale for every dictionary unit.  But all
> the units are available under interval and rato (in fact,
> formattedDateTimeUnit also appears under ratio!).  Is there a way to
> represent our prior knowledge of scale so that applications can provide
> some guidance to users? 
> 
> Tim.


-- 
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Matt Jones                                    jones at nceas.ucsb.edu
http://www.nceas.ucsb.edu/    Fax: 425-920-2439   Ph: 907-789-0496
National Center for Ecological Analysis and Synthesis (NCEAS)

Interested in ecological informatics? http://www.ecoinformatics.org
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