On Aug 6, 2009, at 2:18 PM, Joe Collins wrote: (01)
> 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.
>
> I don't understand what this last statement refers to, "'trope'
> language". (02)
The term 'trope' is a philosopher's coinage. It means, a particular
instance of a property as distinguished from the thing that bears that
property. So, for example, if the color red is a property of things,
then the particular red of the mute button on my desk phone is a
trope. This is more specific than a particular red: some other thing
may have the exact same *color*, be the exact same shade of red, and
yet its color trope will be distinct simply because it is *that*
thing's color rather than my mute button's color. (03)
If this does not seem to make sense, then I suspect that your
intuition will agree with mine, that tropes are not a useful notion in
ontologies. (04)
> (I am not a language maven: more a physicist).
>
>> 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.
>
> 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. (05)
BUt that is not the essential point. Even if they did return the exact
same value, they would still be distinct length-instances, if they
were tropes. Their identity is determined by the things they are
lengths of, not by their values. (06)
But in any case, I think your claim here has to be treated as wrong.
We do in fact often say that two things have the same length. Entire
economies depend upon large numbers of distinct things having
identical dimensions (and hence being interchangeable); the very ideas
of a casting or a pattern depend on this kind of assumption. (07)
>
> 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).
>
> If this is the intention of the UML model, I would agree with that
> intention. (08)
Can you say why? Bear in mind that the presumption here is that the
numerical measures of length are *identical* in these cases. (09)
>> (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.)
>
> Unfortunately, I cannot answer, since I do not fully comprehend
> these distinctions.
>
>>>
>>> "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.
>
> 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)
NOt the value, but a special property which applies only to that one
object, and which has no value at all when applied to any other
object. You could think of it as a particular measurement, in fact, as
opposed to a measurement type or measuring method. (011)
Pat (012)
>
>> Pat Hayes
>
>
> Joe C.
> --
> _______________________________
> Joseph B. Collins, Ph.D.
> Code 5583, Adv. Info. Tech.
> Naval Research Laboratory
> Washington, DC 20375
> (202) 404-7041
> (202) 767-1122 (fax)
> B34, R221C
> _______________________________
> (013)
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