Dear Simon,
Just a few details to add:
On 4/1/2017 10:52 μμ, Simon Spero wrote:
On Jan 3, 2017 6:06 PM, "Robert Sanderson" <[email protected]
<mailto:[email protected]>> wrote:
All currency amounts have an absolute value that changes
constantly due to inflation and markets, and there’s no way to
associate a date with the amount instance to capture this.
The value of $1 (USD) is $1 (USD). The purchasing power may vary over
time, but nominal value remains the same.
Absolutely!
If you have an account holding 2000 Brazilian Reals, this may have
been worth $1000 (USD) in 2014, but only be worth $500 (USD) in 2016;
the value in Reals is unchanged.
Actually, conversion rates may change in seconds, once they are traded.
When redenomination of a currency occurs, a new ISO 4217 code is
assigned.
That solves an ambiguity!
As a thought experiment, if the unit of an “inch” were to change
definition to be exactly 2.5 centimeters, then I believe from the
description of Dimension, that the lengths would remain the same
in absolute value, and we would need a new unit for “new inches”.
Strangely enough, the length of an inch has changed in the past.
"In 1959, the International yard and pound
<http:///wiki/International_yard_and_pound> agreement defined the
international yard as 0.9144metres, and the imperial and US yards were
redefined accordingly.
This resulted in the internationally accepted length of the imperial
and US customary inch being exactly 25.4 millimetres. The
international inch is 1.7 millionths of an inch longer than the old
imperial inch, and 2 millionths of an inch shorter than the old US
inch." (Wikipedia: Inch)
Great! Once we have a date for any Dimension association, even that does
not cause any ambiguity.
I'd like to add, that all physics units are redefined relative to their
empirical base definition as precision of instruments increase. This
pertains also to absolute time.
Best,
Martin
Simon
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