[eml-dev] Revisiting the <measurementScale> categories

[David Blankman]

Inigo,

In addition to the points that Matt made about  measurementScale there are
other measurements that don't fall into any of the categories such as
degrees/angular measurements. Originally these concepts were developed by
social scientists as a way of determing what kinds if statistical tests
would be valid. For example, factor analysis is not supposed to be performed
on ordinal data. In practice, however, factor analysis is routinely done on
Likert scales which are ordinal.

If i remember coreectly, none of us were really satisfied with the use if
measurementScale, however, we needed something and it was a workable, though
clearly not perfect solution.

On another matter, I have been working with GEO-Bon and was talking to Dawn
\field. She directed me to some work that was being considered to extend EML
to deal with molecular data. Has that progressed?

David
On Fri, Sep 19, 2008 at 6:31 PM, inigo <isangil at lternet.edu> wrote:

>
>
> For the record too. The <measurementScale> categories -- nominal, ordinal,
> ratio, interval and datetime -- are not the best solution to classify the
> recorded measurables in a data table.  The categories are not exempt from
> controversy, and the guidelines and attempts to explain the proper use and
> dissection of variable types have not succeeded in different uses.
>
> Example.  a "date" has been documented sometimes as "datetime", but also as
> a "nominal or ordinal" and event "interval or ratio" - wonderful spread.
> these type of classification ambiguity is normal to certain extent, but
> something can be done to improve both the efficiency of the data
> documentation and post-processing and community agreement on practices.
> a good number of LTER sites have in practice simplified these categories
> further.  essentially, there are 'dates', 'quantifiable measurables' and
> 'all the rest' ( all the rest includes free text such as comments,
> identifiers, pair of code-code definitions, nominals and ordinals).  This
> practice has been adopted to remove part of ambiguities that the original
> categories present, and for clarity of use.  a few people may feel that the
> differences between those categories is crystal clear - no doubt - but i
> have not found many of those.
> If exploring different categories (identifiers, codes, quantifiable
> measure, text, flags, dates..) for EML is something that no eml-dev is even
> willing to consider, perhaps reducing the number from 5 to 3 would be a
> humbler goal for the sake of efficiency.  Sure, someone may be tempted to
> divide an interval type by a ratio type with undesirable results as a
> consequence, but i think the risk is still there now (because of the use in
> practice).
> cheers, inigo
>
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