Pat Hayes wrote:
>
> On Aug 5, 2009, at 8:39 AM, Joe Collins wrote:
>
>> Comments referring to the UML model:
>>
>> A given "particular quantity" is composed of a number and a reference.
>>
>> The "particular quantity" you refer to is what SI/VIM simply calls a
>> "quantity",
>> (not to be confused with "derived quantity" or "base quantity")
>> defining it as
>> the "property of a phenomenon, body, or substance, where the property
>> has a
>> magnitude that can be expressed by means of a number and a reference".
>
> I think this is not what is meant, if I understand the 'trope' language. (01)
I don't understand what this last statement refers to, "'trope' language".
(I am not a language maven: more a physicist). (02)
> Take a concrete case, a measurement of length in meters and two
> identical sticks A and B, with exactly the same length. There is one
> property here, called "length", which applies to both sticks and
> produces the same value in each case, say 3.1 meters. So: two sticks,
> one property, one length value of that property. (03)
I would say two length values because any length value is only determinable by
measurement. Two sticks, two length measurements. Given that all measurements
have finite precision, it is unlikely that multiple measurements of even one
stick's length will always happen to return the same magnitude. (04)
As I understand the
> intention of the UML model, however, there would be two particular
> quantities: the particular length of A and the particular length of B,
> which are distinct, but have the same number and reference values
> (respectively 3.1 and meter). (05)
If this is the intention of the UML model, I would agree with that intention. (06)
>
> (This illustrates why formalisms are so much more use than words, by the
> way, when fixing this stuff. Words are ontologically floppy. For another
> example, when you say, above, that something is "composed of" a number
> and a reference, do you mean that it is literally the pair of those
> things? Or that those are defining properties of it? Or simply that
> those are properties of it? These would all give different
> formalizations in an ontology.) (07)
Unfortunately, I cannot answer, since I do not fully comprehend these
distinctions. (08)
>
>>
>> "Quantity value" is most generally a number and a reference to a
>> measurement
>> procedure. In the usual case where the quantity value is a
>> (multiplicative)
>> product of a number and a measurement unit, the measurement unit
>> refers to a
>> part of the measurement apparatus (the essential part).
>> For example, in SI, the unit "kilogram" is a reference to the physical
>> artifact
>> stored by BIPM in Sevres, France. The measurement instrument, in this
>> case a
>> weighing scale, is calibrated in terms of the reference. The kilogram
>> standard
>> is the essential part of the measurement apparatus. The numbers that the
>> weighing scale gives for masses are the "numbers" referred to in the
>> definition
>> of "quantity".
>>
>> n.b. - if you change any essential part of a measurement apparatus,
>> like the
>> unit, you change the numerical value.
>>
>> When the quantities are expressible in terms of units, you generally can
>> multiply and divide the quantities, and commonly add or subtract them.
>> In the
>> case of VIM example 7, Rockwell C hardness, forget about that.
>> Hardness values
>> can only be ordered - products, ratios, sums, and differences are not
>> valid.
>>
>> I believe that the VIM definition for "quantity" is most appropriate
>> to your
>> "particular quantity".
>> The notion of "generic quantity" includes what SI/VIM calls "derived
>> quantity",
>> "base quantity" and "quantity dimension", but a "generic quantity"
>> never has a
>> numerical value.
>>
>> Perhaps a more succinct way of saying it is that a "generic quantity"
>> is the
>> *name* of a property
>
> No, don't say that. Names are lexical entities, not things like quantities. (09)
OK. So would you say that a "generic quantity" is the property, which is
possessed by many objects, and a "specific quantity" is the value of that
property possessed by a specific object? (010)
>
> Pat Hayes (011)
Joe C.
--
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Joseph B. Collins, Ph.D.
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