Ingvar, (01)
Matthew and David can give you the official ISO 15926 line. (02)
I will try and give you my understanding (from the coal face). (03)
In my experience with working engineers, especially when they design
artefacts, they need to specify the characteristics of the equipment (and
its components) they are building.
Often, they want to specify the characteristics in a way that does not
presuppose a particular brand as a solution.
So their design data sheets are full of 'properties' that appear to be the
same as the SI units - the example given here is temperature. (Look at the
specification for your washing machine or microwave for a simple household
example.) (04)
However, on closer examination many of the properties turn out to be
dispositional (as in my example) - not suprising if one is designing
something. (05)
When the engineers work with these dispositional quantities, they tend to
need to work with them in a different way from the manifested quantities -
as they behave differently. (In much the same way as one would not treat the
properties soluble and dissolved in the same way - but see they are
related.) (06)
As I said to Pat, one can exclude trying to get to the bottom of these from
the scope, but then this excludes a large chunk of what would be of interest
to many engineers - and an area that needs some light shed on it. I am not
sure yet another UoM standard for SI units etc. is going to change the way
engineers work. Whereas sorting out indirect properties would. But this is
the usual trade-off between how easy something is and the value it can
deliver. (07)
These dispositional properties also occur (as you know) in science. A
temperature example is the boiling point of water - where (as the history of
temperature illustrates) there are the usual ceteris paribus concerns. (BTW
are you familiar with Hasok Chang's work http://www.ucl.ac.uk/sts/chang/ -
it was a surprise to me that it is only 100 degrees until special
conditions) (08)
So bottom line, broadly speaking: direct = manifestation, indirect =
dispositional. (09)
Regards,
Chris Partridge
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> -----Original Message-----
> From: uom-ontology-std-bounces@xxxxxxxxxxxxxxxx [mailto:uom-ontology-std-
> bounces@xxxxxxxxxxxxxxxx] On Behalf Of ingvar_johansson
> Sent: 01 October 2009 22:03
> To: uom-ontology-std
> Subject: Re: [uom-ontology-std] What is mass?
>
> Pat H wrote:
>
> > Chris Partridge wrote:
> >
> >> Pat,
> >>
> >> The direct/indirect distinction was raised by Matthew and can be
> >> found in
> >> ISO 15926. Matthew or David can give you the latest links if you
> >> cannot
> >> google it.
>
> > Direct vs. indirect UNITS is one notion, coming from metrology, which
> > I kind of grok and understand we must live with, though I don't think
> > there is very much to say about it in a units ontology other than to
> > provide it as a classification without any definition. Direct vs.
> > indirect PROPERTIES is not a notion from metrology, and I am not happy
> > living with it, and I have not yet seen anyone explain what it is
> > supposed to mean. I suspect it has no meaning at all. Direct vs.
> > indirect QUANTITIES I presume means simply, quantities measured using
> > direct vs. indirect units. (if this presumption is wrong, please
> > someone enlighten me.) But please, let us not get units, properties
> > and quantities all confused with one another.
>
> Please, Chris, Matthew, or David, expalain what the ISO distinction
> between direct and indirect properties amounts to. I think I am even more
> confused than Pat. Neither VIM nor the SI contains any distinction between
> direct or indirect units or properties, but they contain a distinction
> between base units and derived units. In the philosophy of measurement, on
> the other hand, there is since long a distinction between direct and
> indirect measurement. In H. Kyburg's book "Theory and Measurement" the
> chapter about direct measurement (5) starts as follows:
>
> "By 'direct measurement', I mean measurement which does not depend on the
> measurement of any other quantity."
>
> And the chapter about indirect measurement (6) starts as follows:
>
> "Temperature, density, and velocity are commonly cited as examples of
> quantities that admit only of indirect measurement. Indirect measurement
> is taken to involve empirical laws or definitions."
>
> The Wikipedia entry on ISO 15926 gives no explanation of the distinction
> between direct and indirect properties. It merely says: "indirect property
> type (e.g. the class "cold locked rotor time")." So once again, please,
> explain the distinction.
>
> Best,
> Ingvar
>
>
>
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