## Bug #1201

closed### Changes to Attribute dialog

0%

**Description**

a) - species lists:

add taxonomic lookup to attribute dialog

if NOMINAL: "are definition for these codes found in another table?"

enable user to choose relevant columns from a table that has already been imported,

and then reference these in the metadata

b) changes:

MeasurementScale Radio Buttons:

i) add "Help" button adj to "Select & define a MeasurementScale:" - pops up a larger

dialog that lists documentation in more detail for these choices.

ii) Revise displayed one-line descriptions (Matt & mark will help with revised

descriptions), eg:

NOM - use M & F instead of 1 & 2 in example text

interval - celsius example not good

#### Updated by Matt Jones about 19 years ago

For b) I suggest the following new text (which still may be too long):

`Nominal: unordered categories or text strings (e.g., Male)`

Ordinal: ordered categories (e.g., Low, High)

Interval: values from a scale with equidistant points (e.g., 12.2 meters)

Ratio: interval scale with a meaningful zero point (e.g., 273 Kelvin)

Date-time: date or time values from the Gregorian calendar (e.g., 2002-10-14)

For the help box:

Help on Choosing a Measurement Scale

------------------------------------

The concept of a measurement scale as defined by Stevens is useful for

classifying data despite the weaknesses of the approach that have been pointed

out by several practitioners. In particular, the classification allows us to

determine some of the mathematical operations that are apporpriate for a given

set of data, and allows us to determine which types of metadata are needed for

a given set of data. For example, categorical data never have a "unit" of

measurement.

Here is a brief overview of the measurement scales we have employed in EML.

They are based on Steven's original typology, with the addition of "Date-Time"

for purely pragmatic reasons (we need to distinguish date time values in order

to collect certain essential metadata about date and time representation).

NOMINAL

The nominal scale places values into named categories. The different values

within a set are unordered. Some examples of nominal scales include

gender (Male/Female) and marital status (single/married/divorced). Text

fields should be classified as nominal.

ORDINAL

The ordinal scale places values in a set order. All ordinal values are also

nominal. Ordinal data show a particular value's position relative to other

values, such as "low, medium, high, etc." The ordinal scale doesn't

indicate the distance between each item.

INTERVAL

The interval scale uses equal-sized units of measurement on a scale between

values. It therefore allows the comparison of the differences between two

values on the scale. With interval data, the allowable values start from

an arbitrary point (not a meaningful zero), and so there is no concept of

'zero' of the measured quantity. Consequently, ratios of interval values

are not meaningful. For example, one can not infer that someone with a value

of 80 on an ecology test knows twice as much ecology as someone who scores

40 on the test, or that an object at 40 degrees C has twice the kinetic

energy as an object at 20 degrees C. All interval values are also ordered

and therefore are ordinal scale values as well.

RATIO

The ratio scale is an interval scale with a meaningful zero point.

The ratio scale begins at a true zero point that represents an absolute

lack of the quality being measured. Thus, ratios of values are meaningful.

For example, an object that is at elevation of 100 meters above sea level

is twice as high as an object that is at an elevation of 50 meters above

sea level (where sea level is the zero point). Also, an object at 300

degrees Kelvin has three times the kinetic energy of an object at 100

degrees Kelvin (where absolute zero (no motion) defines the zero point of

the Kelvin scale). Interval values can often be converted to ratio

values in order to make ratio comparisons legitimate. For example, an

object at 40 degrees C is 313.15 degrees Kelvin, an object at 20 degrees C

is 293.15 degrees Kelvin, and so the first object has approximately

1.07 times more kinetic energy (note the wrong answer you would have

gotten had you taken the ratio of the values in Celsius).

DATE-TIME

Date and time values in the Gregorian calendar are very strange to use

in calculations in that they have properties of both interval and ratio

scales. They also have some properties that do not conform to the

interval scale because of the adjustments that are made to time to account

for the variations in the period of the Earth around the sun.

While the Gregorian calendar has a meaningful zero point, it would be

difficult to say that a value taken on midnight January 1, 1000 is twice as

old as a value taken on midnight January 1 2000 because the scale has

many irregularities in length in practice. However, over short intervals

the scale has equidistant points based on the SI second, and so can be

considered interval for most some purposes, especially with respect to

measuring the timing of short-term ecological events. Date and time values

can be represented using several distinct notations, and so we have

distinct metadata needs in terms of specifying the format of the value

representation. Because of these pragmatic issues, we separated Date-time

into its own measurement scale. Examples of date-time values are

'2003-05-05', '1999/10/10', and '2001-10-10T14:23:20.3'.

#### Updated by Matthew Brooke about 19 years ago

b) fixed by perumal. a) still current

#### Updated by Matthew Brooke about 19 years ago

part (b) has been resolved. Part (a) has been moved to its own new bug, which is

now bug 1250