Re: Ed Barkmeyer's suggestion to leave currencies until after we get
agreement on physical units of measure - no problem, the amount of
discussion already suggests that it may be more of a distraction than it
it's worth at this point. (01)
But as for what a currency measures - the best approximation to the actual
value, in certain official measures (Consumer Price Indices) is the amount
of some assortment (a standard 'basket', varying over time) of goods it will
buy. The price of gold is sometimes used as an inaccurate surrogate measure
for the actual value in purchasing anything that is for sale. Of course
there would be details to pay attention to: as for exchange rates, as Martin
Weber points out, there is a buy and sell rate for each pair of currencies,
and it seems straightforward to take the mean as the actual exchange rate,
with the differential being the transaction fee, symmetrical in both
directions. The daily fluctuations are so large that I can't think of any
reason to try for any more elaborate definition of currency value ratios (we
aren't building a trading model to make money). (02)
As the discussion of 'force' suggests, we can get into extended discussion
even of the seemingly more objective physical measures. I am still not
certain that currency will be any less amenable to agreement, but leaving it
out gives us one fewer issue to deal with, and that is probably a good
thing. (03)
Pat (04)
Patrick Cassidy
MICRA, Inc.
908-561-3416
cell: 908-565-4053
cassidy@xxxxxxxxx (05)
> -----Original Message-----
> From: uom-ontology-std-bounces@xxxxxxxxxxxxxxxx [mailto:uom-ontology-
> std-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Ed Barkmeyer
> Sent: Monday, August 10, 2009 5:44 PM
> To: uom-ontology-std
> Subject: Re: [uom-ontology-std] retitled - hardness etc.
>
> Patrick Cassidy wrote:
> > It is an exaggeration to say that modeling a currency unit requires
> > elaborate modeling of everything related.
> There are two relevant questions:
> (1) What aspects of the related concepts are needed to make the
> currency
> ontology useful?
> (2) What aspects of David's draft model (or some other draft of a uom
> ontology) apply to them?
>
> Currency is a 'quantity kind', if you will, and I suppose one can talk
> about 'particular quantities' that are instances of the Q1 of currency.
> But there is no Q3, no amount that is independent of representation --
> there are only quantity values. But the Q3 is the supertype of
> 'measurement unit'. So if the euro is a measurement unit, what
> abstract
> amount of stuff in the currency dimension does it represent? How is it
> defined?
>
> Currencies don't properly belong to a system of units that is related
> to
> a system of quantities. Perhaps we could treat each national/regional
> currency as a system in its own right. But conversion of units between
> those systems isn't fixed. There is no conversion formula. As Pat
> says:
> > There are multiple currency
> > units, and between them there are exchange rates (which change daily),
> And there are multiple financial instruments that are valued in
> currencies and have different exchange rates based on the practices of
> their respective markets. So the concept of "conversion of units" is
> entirely different.
> > and
> > any number x times the base unit is indeed x multiples of the base
> unit, and
> >
> So the concept 'quantity value' seems to be properly supported, except
> for how the base unit itself is defined.
> > the way one 'measures' or 'standardizes' the base unit is as its
> value on
> > any given day versus some one or more other freely exchangeable
> currency
> > units, and one may also use the price of gold (on an open market
> without
> > restrictions) as a measure of value.
> I think that definition is circular. If every currency unit is
> specified by its ratio to some other currency unit, we have the
> "turtles
> all the way down" problem. At least one of them must be defined in
> terms of something else, like a weight of specie (gold, silver, cows,
> whatever). Unfortunately, I don't think any of them has been so
> defined
> for years.
>
> "the price of gold (on an open market without restrictions)" is
> fictitious. As Martin Weber observes, the actual realization process
> affects the actual value. I suppose it might be specifiable with some
> uncertainty, but it is hardly a fixed reference. We can argue about
> whether measurement units are truly invariant, but there is no argument
> about currency -- it is not. And that means that all the referential
> concepts, and all the regulatory and industrial practices, that depend
> on repeatability of measurements do not apply to currency.
> > The 'measurement' method is a currency market,
> which measures what property of what thing as a calibration point? Or
> perhaps the question is: which currency market? Is there an
> "international standard currency market" (the IMF? the World Bank?),
> like the International Standard Kilogram?
> > and for the same reason were are not going to represent measuring
> > devices, we do not need to represent the details of a 'currency
> market',
> > though a bare placeholder type may be useful. The only other
> ancillary
> > concept we may want is an 'issuing authority', which will be a
> 'national
> > government', which can also be a undefined placeholder. If we are
> going to
> > represent the 'authority' that defines the base unit of physical
> measures,
> > then defining the authority that issues a currency will be close
> enough to
> > represent no problems.
> >
> So we are not going to model the concepts that give currency its
> meaning
> and its utility, which goes to issue (1) above.
> > If the majority prefer to exclude currencies from the UoM ontology, I
> have
> > no objections, but I don't foresee major problems including currency.
> I do. This is simply false analogy. Yes, currency is represented by
> (number, unit), and that is the entirety of its similarity to units of
> measure. Relative to issue (2) above, the rest of the ontological
> concepts are doubtful or clearly inapplicable. What concerns me is
> that
> the attempt to support this largely different concept might well cause
> our ontology to be robbed of useful axioms, because they don't apply to
> this extraneous case. And at the other end, we will surely provide
> nothing of value to the finance industry.
>
> Rather than assuming that our ontology might apply to currency, I
> suggest we build the ontology to address scientific and industrial
> units
> of measure, and evaluate the applicability of the axioms to currency
> when we are done. La prova e nel gusto -- the proof of the pudding is
> in the taste.
>
> -Ed
>
> --
> 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
>
> "The opinions expressed above do not reflect consensus of NIST,
> and have not been reviewed by any Government authority."
>
>
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