Dear Mike, (01)
I do not think that euro, dollar, yen, etc. should be within scope, any more
than "6 inch wire nail", "10 X 150 galvanised coach bolt", etc.. (02)
These are just classes of item of which you can have one or more. I can
enter into a contract which says "on the 1st of October 2009 I will pay 1
million euro into your account in Frankfurt, and on the 1st of April 2010
you will pay 1.5 million dollars into my account in New York". Similarly I
can enter into a contract which says "on the 1st of October 2009 I will
deliver 100 thousand 6 inch wire nails to your site in Essen, and on the 1st
April 2010 you will deliver 10 thousand 10 X 150 galvanised coach bolts to
my site in Gary IN". (03)
Both are valid contracts. The notion that there is a kind of quantity called
"value" which can be expressed in units of euro, dollar or "6 inch wire
nail" is dubious and I think that we should keep well clear :). (04)
Best regard,
David (05)
At 15:25 09/08/2009 +0100, you wrote:
>... and some of which rely on no physical laws at all, e.g. currency units.
>
>Mike
>
>David Leal wrote:
>> Dear Josh,
>>
>> I don't think that we disagree substantially. The kind of quantity
>> "thermodynamic temperature" is defined by reference to a physical law. The
>> Kelvin is defined by a physical law and by reference to an arbitrary fixed
>> point - the triple point of water. However the ITS90 scale is not defined
>> with respect to either a physical law or the Kelvin - it is an arbitrary
>> scale which is defined by a measurement process and which has been shown by
>> experiment to be close to the scale derived from Kelvin.
>>
>> I think we agree that the ontology needs to encompass different types of
>> quantity, unit and scale - some of which rely upon illustrious physical laws
>> and some of which rely upon rather weak ones. In the case of Rockwell C
>> hardness, the "physical law" is very weak. It is merely that the values
>> provided by the measurement procedure are consistent with one of the
>> intuitive understandings of hardness - an ability to resist damage when
>> impacted by a hard pointed object.
>>
>> Best regards,
>> David
>>
>> At 16:54 07/08/2009 -0400, you wrote:
>>
>>> David,
>>>
>>> Temperature is not at all defined by the measurable processes you
>>> mention. Those happen to be means of measuring temperature through
>>> models which relate observable processes to a phenomenon of interest,
>>> namely temperature. The models may rest on more or less illustrious
>>> theories, e.g. laws of thermodynamics versus concept of hardness in
>>> material science. The scale or reference system for relating
>>> coordinates to measurements within the model may be more or less
>>> absolute in those theories, e.g. absolute zero versus spatial or
>>> temporal coordinate systems. Nevertheless, I would contend that they
>>> are always present where units of measure are being employed
>>> meaningfully (or should I say, realistically).
>>>
>>> Josh
>>>
>>> On Aug 7, 2009, at 4:32 PM, David Leal wrote:
>>>
>>>
>>>> Temperature is not merely a
>>>> phenomenon defined by the differential thermal expansion of mercury
>>>> and
>>>> glass or the behaviour of electrons in a thermocouple junctions,
>>>> because we
>>>> have the laws of thermodynamics.
>>>> (06)
============================================================
David Leal
CAESAR Systems Limited
registered office: 29 Somertrees Avenue, Lee, London SE12 0BS
registered in England no. 2422371
tel: +44 (0)20 8857 1095
mob: +44 (0)77 0702 6926
e-mail: david.leal@xxxxxxxxxxxxxxxxxxx
web site: http://www.caesarsystems.co.uk
============================================================ (07)
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