> The art of ontology is the art of not designing something. What you're
> suggesting looks a lot more like a design solution than a representation
> of real things and the way they are.
> Mike (01)
Please, explain in detail what you mean, and how it affects my proposal.
In order to talk about the world we have to design concepts, and in order
to make measurements of properties in the world we have to design scales
with measurement units. Then linguists can study and represent relations
between concepts, and UoM ontologists can study and represent relations
between measurement units. So what? (02)
> ingvar_johansson wrote:
>> A bit below comes a question from an informatics layman.
>> Gunther Schadow wrote:
>>> ingvar_johansson wrote:
>>>> one more comment. You asked:
>>>>> 1 N.m = 1 N.m : true or false?
>>>> and I said 'true' (and so did Pat H). But this does not imply that 1
>>>> of energy = 1 N.m of moment of force, since energy and moment of force
>>>> different kinds of quantities (despite having the same dimension).
>>> and that's precisely my point and why I disagree with Pat Hayes
>>> that this is not useful. I was asking if 1 N.m = 1 N.m and
>>> the answer is ambiguous. The unit is newton-meter, it is not
>>> newton-meter-of-energy, therefore, I would argue, that the unit
>>> is the same even if the kinds of quantity are different. Unless
>>> we agree on this (by either one of us changing our mind) I don't
>>> see a value at looking at ontological constructs.
>>> I don't want to discuss the N.m issue in particular at this
>>> time, only that it's pointless to proceed if there is
>>> disagreement about this matter.
>>> The question remains what we believe jointly that UoM concepts
>>> should do for us. You may want them to preserve the difference
>>> between torque and energy, I don't.
>> Can't you both cancel and preserve the difference? That is, can't you
>> both an over-arching concept 'nominal newton-meter' and a number of
>> subsumed concepts such as 'energy newton-meter' and 'torque
>> each of which brings in what VIM calls a kind-of-quantity?
>>> So the question remains
>>> open on the list. But there is no point in proceeding if we
>>> don't agree on this. We might, however, agree if we use these
>>> example to be more clear about why we have the desire for the
>>> UoM concepts to do what we want them to do and possibly how
>>> else we might get our desires fulfilled.
>>> In my experience with dealing with scientific equations and
>>> computations, the units were incredibly useful for (a) converting
>>> to a unit that I needed and (b) giving assurance that I probably
>>> didn't make some gross error in my equations. Thus, in my
>>> experience with dimensioned terms it does not matter in the end
>>> whether the m in N.m, was the length of a lever or a distance
>>> of displacement, that is all in the concerns that led to my
>>> equations. The units function more like a check-digit at the
>>> end: if the unit term does not agree with the expected kind of
>>> quantity, something went wrong in my calculation or the formula.
>>> This is why around UCUM implementation I use the concept of
>>> a "DimensionedQuantity". A Quantity is any set of values
>>> where at least some values have a difference operation. A
>>> DimensionedQuantity is essentially a number with a dimension.
>>> Such a quantity for example is 16 N.m. Units are themselves
>>> DimensionedQuantities with a name (and the name can be complex
>>> such as N.m or even 16.N.m) So, my ontology behaves exactly
>>> like the symbols that I write on a sheet of blank paper when
>>> I compute my scientific equations. It does not do more nor
>>> less than what the units do on paper. I.e., 1 N.m = 1 N.m
>>> = 1 kg.m2.s-2 = 1 J.
>>> There is nothing you can do to separate these concepts unless
>>> by assuming into your theory the detail of all of mechanics
>>> (and all of science) which you can't do.
>>> BTW, it is not true that N.m of torque and joule of energy
>>> are completely unrelated. Because the torque times angle
>>> moved is again your energy. Whether or not we maintain a
>>> dimension for angle in UCUM is also besides this point. Of
>>> course: by adding more distinct dimensions we may be able
>>> to preserve more distinctions and by having less dimensions
>>> we lose distinctions that we can make by just looking at
>>> number and unit. But because I do not expect much more than
>>> the function of a "dimensional check digit" and defined
>>> conversion rates from the units, I can give or take a few
>>> dimensions without much trouble. The only place were I really
>>> get into trouble is where we haven't even started to discuss,
>>> i.e., idiosyncratic "procedure defined units".
>>> Gunther Schadow, M.D., Ph.D. gschadow@xxxxxxxxxxxxxxx
>>> Associate Professor Indiana University School of Informatics
>>> Regenstrief Institute, Inc. Indiana University School of Medicine
>>> tel:1(317)423-5521 http://aurora.regenstrief.org
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> Mike Bennett
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