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gistMagnitude
gist7.1.1 magnitudes
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To have a comparable numerical value. Each magnitude has a unit.
Which unit of measure you are using. All measures are in some uom, even if we don't know what it is initially.
Links a Magnitude to the degree of accuracy of the numeric value. This allows for fuzzy numbers. All magnitudes have a precision. Usually we don't record them. When we do this, it will be a value whose extent covers 2 standard deviations around the stated magnitude
NOTE: Most frequently apples to Magnitude(s) and TimeInstant. Could also apply to a measurement.
EXAMPLE: Temperature precise to tenth of a degree C; TimeInstant precise to 24 hours.
Currencies are rounded to specified precision
Base of temperature is in Kelvin per SI to allow for all units to be expressed relative to a real (in this case absolute) zero.
Temperature
Measure of light
Luminance
Amperage
Electric Current
Amount of a substance as counted molecules. It's here for completeness, in case we bridge to an SI unit conversion ontology. It is unlikely a commercial system, with the possible exception of some involved in chemical research, would use this. Note: I left out the disjointness with Count, Weight and Volume as there is some ambiguity, at least in my mind, as to whether they are mutually exclusive.
Molar Quantity
Measures that involve countable amounts ("eaches" as well as cases, etc.). Can be decimal. Note: we did not make count disjoint with all the other magnitudes as there are some magnitudes that could conceivably be counted (say distance in rods, it's a bit of a stretch admittedly but shouldn't harm anything).
Count
Magnitude of mass. Assumes object is near the earth's surface, so weight and mass are equivalent for our purposes.
Weight
Special type of magnitude due to the way rounding is handled in math and temporal aspect of conversion.
Monetary
Three dimensional space or equivalent fluid measurement.
Volume
Two-dimensional area.
Area
A measure of distance which could be distances over the earth, and could also be height, width, length, depth, girth, etc.
Extent
Time, but not on time line. For instance one week, or seven days, but not Jan 1, 2008 to Jan 7, 2008 (which is an interval). Intervals have durations but aren't durations.
Duration
A scalar value which is either measured, estimated or set as a reference value. Magnitudes of the same dimensional type ( i.e., duration or electric current) can be compared with a greater than or less than operator, but can still differ in their relationToTheWorld type (i.e., you can compare actuals to estimates or references as long as the dimension is the same).
Magnitude
NOTE: Note the precision should be in the same type of unit as the magnitude but we'd need rules to enforce that
Ratio Magnitude
This is a ratio class where the numerator and denominator are of the same unit of measure. This would have to be enforced as a SWRL rule. Note: there are various ways to represent percentage: 50/100 could be represented as "50" or "0.5". We have chosen the later as it involves fewer conversions for subsequent use.
Percentage
These are magnitudes expresses as products of primitives (such as force M*A)
Product Magnitude