Dear all, (01)
As to the scope of UoM, or use cases, the following may help: to define goals
or functionalities that, using the ontology, should be able to be supported.
Please find a start in the table below. (02)
By the way, I'm pleased to see that there seems to be concensus about some
concepts to include. However, as the table below shows, there may be some more
concepts that should be included, such as, in particular "measurement scale",
but also "dimension". All depending on which functionalities we think should be
able to be supported using the ontology. (03)
I have based the table below on examples encountered in the Ontolog emails of
the past months, plus examples I have encountered in supporting quantitative
research (or knowledge if you wish), obvious examples I hope. The first column
lists the functionalities, and the second column gives the concepts and
relations that are (roughly) required to be able to support the functionality. (04)
I would particularly ask attention for conversion of non-ratio scale
quantities, such as temperatures. Converting a temperature difference of 3
kelvin yields 3 degree Celsius (the degree Celsius is officially defined as 1
kelvin); converting an absolute temperature of 3 kelvin, however, yields
-270.15 degree Celsius. The Kelvin and Celsius scales are defined by fixed
points. These fixed points can be defined in terms of each other (for example
0.01 on the Celsius scale is defined as 213.16 on the Kelvin scale) or in terms
of standard quantities (e.g., 273.16 on the Kelvin scale is defined in terms of
the triple point of water). (05)
------------------------------------------------------------------------------------------------------------------------- (06)
Functionality Required
concepts and relations (07)
==========================================================
========================================================== (08)
Unit conversion Units,
definitions of units in terms of other units (09)
Conversion of non-ratio scale quantities Measurement
scales, fixed points, definitions of fixed
(such as absolute temperatures) points in
terms of each other (010)
Data conversion Units,
measurement scales,
definitions of
units and measurement scales in terms
of other units
or measurement scales,
some form of
mathematical semantics (011)
Unit en dimension consistency checking Units,
quantities, dimensions,
relations
between units and quantities,
relations
between quantities and dimensions,
some form of
mathematical semantics (012)
Expressing physical quantities in databases, Quantities,
units, measurement scales
as inputs to and outputs from applications that use
these data (013)
Data integration Quantities,
units, measurement scales,
some form of
mathematical semantics (014)
Give alternative units Units,
quantities, relations between quantities and units (015)
Comparison of quantitiy values (or measures or magnitudes) Quantities,
units, measurement scales, (measures) (016)
<weight uom:unit="kg">1.3</weight> Units,
measurement scales (017)
:myCheeseLump :weight Quantities,
:units, measurement scales, (measures)
[ rdf:value "1.3"^^xsd:decimal; uom:unit uom-si:Kg ] (018)
"True to VIM" Quantities,
units, measures (or magnitudes or quantity
values) (019)
------------------------------------------------------------------------------------------------------------------------- (020)
If we think or decide that all these concepts are important, we can conclude we
need:
- units,
- quantities,
- dimensions,
- measures (or magnitudes or quantity values),
- definitions of units in terms of other units,
- relations between units and quantities,
- relations between quantities and dimensions,
- measurement scales,
- definitions of measurement scales in terms of other measurement scales. (021)
I propose to leave 'some form of mathematical semantics" out of consideration,
as, likely, other ontologies will capture this. (022)
Together with UoM someone can try to accomplish the desired functionality. (023)
Best regards, Hajo (024)
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