Dear Ed, (01)
> Two observations.
>
> Matthew West wrote:
>
> > [MW] The way I would see it, it is about who is responsible for
> what, so
> > rather than having a thousand ontologies for units of measure, we get
> BIPM,
> > or the relevant ISO committee they develop their standards through to
> > develop it, and the rest of us just use it.
>
> 1) what is the ontology for the SI system?
>
> BIPM (www.bipm.org), via the International Vocabulary for Measurement
> (VIM) and the relevant SI standards, provides the "abstract ontology"
> for measurement and units of measure. Formalizing that ontology has
> proved to be difficult. The axioms for the 'quantity' concept require
> ontological commitments on which the VIM is not clear. (02)
[MW] I can imagine. Quantities are surprisingly ill understood, considering
how much we all use them. However, I was actually thinking of something very
weak, that might in fact do little more than give web identifiers for units,
scales, and quantities. Since we seem to manage quite well without
understanding what units and scales really are, it probably won't do much
harm not to say much about them.
>
> One of the problems is the notion of "abstraction of specific
> properties". My computer keyboard is 45cm long. The "specific
> property" is 'is 45 cm long'. The abstraction of that (and "similar
> properties") is the concept "length". What exactly is that
> abstraction? (03)
[MW] Yes. And what is length as opposed to breadth and why? (04)
We had a crack at that in ISO 15926-2 (Diagram 29)
http://www.tc184-sc4.org/wg3ndocs/wg3n1328/lifecycle_integration_schema.html (05)
Since you understand the problem, what we did might just make sense to you.
We had length as an instance of class_of_shape_dimension. Things like
"Maximum allowable working temperature" are arguably even worse. (06)
(I am not proposing what we did in ISO 15926 as anything more than an
illustration of the difficulty you rapidly get into.) (07)
> What axioms does it have? Is it essentially unary or essentially
> binary?
>
> This is the "ontology in your head". We have a working knowledge of
> the
> concept 'length', and, for practical purposes "it doesn't make a
> difference what ontological commitment you make". But if you make
> different commitments, you get different axioms. What we really mean
> is
> that we conflate two closely related concepts, because we can make the
> proper interpretation in each case. But the axioms distinguish them --
> only one of them is 'length'. (08)
[MW] Yes. As I said above, I would simply not add the axioms, and then there
would be no conflict. An alternative would be to give both cases and the
mapping between them, so it did not matter which one anyone used, you
would automatically have inferred the other.
>
> 2) "the rest of us just use it" is the key
>
> There are dozens of measurement systems in use internationally. But
> international commerce was greatly hampered by their use in trade. So,
> to the monetary benefit of nearly everyone, the major trading partners
> agreed on a standard system of measures that could be used directly for
> trade, or at least used as the reference for other measures. (But that
> didn't happen until 1876, well after the Europeans invaded oriental and
> African trade, and "interchangeable parts" made independent
> measurements
> a manufacturing issue.) And "the rest of us just use it" because of
> the
> Golden Rule -- the people who had the gold made the rules. (09)
[MW] Well yes. The reason I was suggesting units was just that, there is
high value in agreeing, and we have, for practical purposes.
>
> The problem with upper ontologies and reference ontologies is that
> there
> have to be enough people with the gold who see a reason to make any
> given ontology a reference. And that means there must be enough use of
> ontologies generally to make the cost of not having a common reference
> noticeable to the guys with the gold. (010)
[MW] I was not thinking of upper ontologies, though it is difficult I agree
to do any ontology without making upper level commitments.
>
> IMNSHO, we should stop talking about reference ontologies until we have
> a large and economically or politically important community of
> practice.
> Then, the value of reference ontologies will become clearer, and
> there
> will be motive and money to adopt them or construct them. But as long
> as our communities are only the farmers in a 20-km radius, the cup in
> the general store and the clock in the Post Office are good enough
> standards. (011)
[MW] Well I was looking in an open catalogue system a year or so ago that
allows the addition of whatever you want, and just for fun I decided to look
for Celsius. I found 6 or 7, including one that was correct (but which was
not my guess at what was correct). I would be pleased just not to have that
confusion. (012)
Regards (013)
Matthew West
Information Junction
Tel: +44 560 302 3685
Mobile: +44 750 3385279
matthew.west@xxxxxxxxxxxxxxxxxxxxxxxxx
http://www.matthew-west.org.uk/ (014)
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