Dave McComb wrote:
> I took it to mean they were making a distinction between a particularly
> measured thing (Johny is 4 feet tall) (which we call a measure) and a
> reference (you must be 52 inches tall to ride on the Thunder Mountain Ride).
> In the second case nothing was measured, someone just made up a reference
> value. (01)
I don't think that is what is being distinguished in the secton of the
VIM that David and Martin pointed to. The distinction in Dave's example
is the one I was making between a 'particular quantity' and the
abstraction of it that I attributed to the VIM term 'magnitude of a
quantity'. The "52 inches" is a quantity value that expresses a
magnitude without reference to a particular quantity. (02)
> The other distinction they were calling out "quantity in a general
> sense" seems to me is just the TBox for the particular "dimension"
> (i.e. "length") (03)
Yes. It is a T-box/class/category of particular quantities. (04)
> The points about being place in order, and grouping seem to refer to
> the "dimension" (we can compare the length of the Themes to the
> distance to the sun because they are both measures of distance
> (or have dimension "length" (05)
Yes. (06)
> or even better both have a base unit of "meter" which really makes
> them comparable) (07)
"comparable" is a source of confusion. The distance from the Sun to
Jupiter is "comparable" to the distance from my chair to the door, full
stop. That is because they are both quantities of the "length" kind.
If one is expressed in astronomical units and the other in metres, the
_quantity values_ are not directly "comparable" numerically -- comparing
the "numbers" is only meaningful when the "units" are the same. (08)
(I think this is what Dave was saying.) (09)
-Ed (010)
--
Edward J. Barkmeyer Email: edbark@xxxxxxxx
National Institute of Standards & Technology
Manufacturing Systems Integration Division
100 Bureau Drive, Stop 8263 Tel: +1 301-975-3528
Gaithersburg, MD 20899-8263 FAX: +1 301-975-4694 (011)
"The opinions expressed above do not reflect consensus of NIST,
and have not been reviewed by any Government authority." (012)
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