Hey, Joe, I don't have the energy to argue the Large Issues with you,
and in any case I'm not interested. Suffice it to say that a large
amount of the world's business, particularly business in which
formalized data models and formal ontologies are involved, *does*
proceed without mentioning probabilities or tolerance ranges of
measurements. As for the whole of theoretical physics being 'garbage
in' which only 'looks good on a marquee', I guess that comment places
your position firmly out in left field as far as I am concerned. (01)
Take it from me, if our ontology cannot proceed without first ignoring
probabilities and tolerances and degrees of accuracy, etc., and cannot
assume that numerals simply denote actual, exact, numbers, then it
will not get done. (02)
Other comments below. (03)
Pat (04)
On Oct 8, 2009, at 3:35 PM, Joe Collins wrote: (05)
>>>> I take a third way: I am agnostic on 'true' values.
>>>> Why do we need such an hypothesis, anyway?
>>> Because communication is virtually impossible without this
>>> hypothesis, and because it underlies virtually all of science.
>>> Equations like e=mc2 do not refer to measured values with
>>> tolerance ranges and probabilities of error, they refer to mass
>>> and energy. That these quantities can only be measured to a
>>> certain degree of accuracy is true, but irrelevant to what the
>>> equations say. DIfferential equations, in fact, only make sense
>>> when the reality they purport to describe is assumed to have
>>> differentiable fields in it, which are *inherently* unmeasurable
>>> with complete precision. Still, people do use the equations to
>>> make predictions.
>
> And "garbage in, garbage out" will apply.
> The notation of physics, such as e=mc2, looks good on a marquee, but
> is notoriously terse.
> There is no specification of dimensions and units, either: does that
> mean they are unnecessary to specify?
> Anyone who has tried to apply e=mc2 to a real-world problem will
> tell you that "of course you must account for the uncertainty..."
>
>>>> In a model, any numerical value you bind to the quantity, Q, that
>>>> suggests that that value is the unique, true value of the object
>>>> in physical reality that Q refers to, is a lie. You can only bind
>>>> a received value to Q, and those values are ultimately received
>>>> through some form of measurement process.
>>> This is a philosophical position, but (with respect) you are not
>>> making a very good philosophical argument in its defense. Rather
>>> then engage in this debate, which I don't have the energy for, all
>>> I can say is, your view is the minority, and ontology-writiing
>>> simply isn't workable without basing it on a more realist
>>> perspective.
>
> I think we disagree on what a realist is. (06)
I mean, a perspective in which the reality of the external world is
assumed, and we set out to describe it. As opposed to a perspective
that says that all talk of physical things must be reinterpreted as
talk about measurements, since results of measurements are the only
things we can know for sure; which I refer to (somewhat tersely) as
'operationalist'. (07)
> The philosophical perspective I am defending is close to what I
> believe the metrologists that authored the SI & VIM had in mind.
> I took it that the SI & VIM should serve as a basis for a UoM
> ontology. (08)
For the metrology concepts, but not necessarily for the philosophy. (09)
> Without much justification you are picking and choosing what may be
> ignored from that standard. I am defending the position that
> uncertainty is an essential part of the standard.
>
>>>> It seems you are saying that the model we create has more
>>>> importance than the knowledge that proves the validity of the
>>>> model.
>>>>
>>>> I believe it is antithetical to a scientific perspective to
>>>> accord more importance to any single model of reality than to our
>>>> measurement data upon which the models rest.
>>> Fair enough. I disagree (and I suspect most scientists would), but
>>> I'm happy for you to believe that Im not a scientist. We aren't
>>> doing science in this forum, we are building an ontology.
>
> If you are building models that can be validated, then, in my mind
> you are doing science. This encompasses applied science
> (engineering) as well. Application of the scientific method is not
> so esoteric as you make it sound: it is essential to sound
> engineering practice.
>
> If you are building models with no intent to validate them or that
> cannot be validated, then you are not doing science or engineering. (010)
I believe that is what I said, above. So we agree. (011)
>
> The only validation you can perform in your ontology without
> expressing uncertainty is strict equality. You'll have no other
> notion of closeness or close enough. In any practical sense this
> means that your model can never be validated: you will almost never
> see values exactly equal to what you predict, and you'll have no
> idea how far off your model is in its predictive capability.
>
> What use is there for a model that cannot be validated? (012)
Thousands of uses. Too many to list. Most data models in actual use
have not been validated in the sense you are using the term, ie
checked against physical measurements of some kind. (013)
>
>>>> Earlier on this reflector the case of the problematic concept of
>>>> "boiling temperature of water" was pointed out. You may have a
>>>> nice model/theory of phase transitions, but since a (unique)
>>>> boiling temperature can be difficult to measure, reality shows
>>>> itself to be messier than the model. We cannot just assert in the
>>>> face of the evidence that there is a true boiling temperature.
>>> Actually, yes we can. And people do, and the business of the world
>>> depends on such assertions. Not every user of units is a scientist
>>> with a non-realist metaphysics.
>
> Ouch! Have you just thrown me into a philosophical dungeon?
>
> This reminds me of Feynman's description of cargo cult science.
> If you build a model with no expectation of being able to validate
> it, your activity is on a par with that of a cargo cult practitioner.
> Ineffective as the activity may be, plenty of people may still do
> it, but that's not a valid argument to join the crowd. (014)
Actually it is. I have no ambition to set the world to rights or to be
an ambassador (missionary?) for any particular philosophical
viewpoint. Our task here is simply to formalize the ideas of units,
quantities and maybe measurements so that as many people as possible
can use them for their business, whatever that happens to be. If they
are running a cargo cult, thats not our problem. (015)
>
>>> They are when they ignore questions of how quantities are
>>> measured, accuracy, etc., and simply refer to values, which they
>>> often do. The weight of my car is given in kilos. It does not come
>>> with an error estimate or a tolerance interval: it is expressed
>>> simply as a numeral. Now, this numeral, when used in an ontology,
>>> must refer to something. What is certainly *seems* to refer to is
>>> a weight, specified using a scale calibrated in kilograms. An
>>> *actual* weight, *the* weight of my car. If there is no such thing
>>> as the actual weight, then I cannot refer to it, and must use some
>>> other way to specify what '5647 kilos' means. So, what, in your
>>> view, are we to say about such language? That is is simply wrong,
>>> and should be rejected? Or that it is an abbreviation of a much
>>> more complicated assertion not about actual weights at all, but
>>> rather about measurements of weight, perhaps referring to the
>>> apparatus that was used to measure the weight of my car? (But what
>>> if there is no such apparatus, and the weight has been calculated
>>> in some way rather than measured? Is it then no longer a weight,
>>> but only a pure-mathematical entailment?) Or that a tolerance
>>> interval must exist, even if we do not know what it is, so this
>>> must be expressed as an existential claim about an unknown
>>> tolerance interval? (But that could be any interval: surely we
>>> want to say more about it, perhaps that is a 'reasonable' such
>>> tolerance interval for things of this kind - so we need to talk
>>> about what kind of thing the car is, and have an overarching
>>> ontology of reasonableness of measurements for certain
>>> purposes...) But all I wanted to say, and all that the shipping
>>> company needed to know, was how much my car weighs, expressed in
>>> kilos.
>>> There is a deeper argument, in any case. Take a tolerance interval
>>> as an example. You want to say that 4.0 'really' refers to the
>>> interval [3.95, 4.05] , because exact quantities may not even
>>> exist. But that interval expression itself uses exact quantities,
>>> viz. 3.95 and 4.05. Indeed, given your rules here, these are more
>>> exact than the original, having two decimal places: so each of
>>> these must really be an interval: 3.95 is [3.945, 3.955]. And that
>>> in turn is [[3.9445 3.9455] [3.9545 3.9555]] And so on ad
>>> infinitum. Now, one can indeed make mathematical sense of these
>>> infinite nested-interval structures, but its a lot more
>>> complicated than the authors of the SI system had in mind, I am
>>> willing to bet. The point being that at some point in this
>>> descent, we usually want to just toss in the towel and say, OK,
>>> I'm referring *exactly* here, just using a numeral to refer to an
>>> *actual number*, a *point* on the rational continuum. And if we
>>> can do that anywhere, then we can do it right at the beginning.
>
> It seems to me that you ignore the details of how any knowledge of
> quantities would actually be used. (016)
I don't agree. Seems to me that you have not answered my point. (017)
> The values of quantities will be used to make decisions.
> If, for example, I am receiving widgets that the shipping list
> specifies as weighing 10 grams, what do I do with that information?
> If I merely acknowledge the receipt of the information, it is of
> little use. On the other hand, if I use that information to make a
> decision, then I must compare it to something.
> Let's say that I weigh three received widgets and I find that they
> weigh 12, 11, and 9 grams. As a receiving clerk, the only idea I
> have if these are acceptable is if they are what is specified on the
> shipping list. I compare those weights to what is on the shipping
> list. Shall I send them back to the manufacturer? Since in your
> ontology only strict equality can be used, they are clearly not what
> is on the shipping list, and an error must have been made, so back
> they go. If instead I have a range of acceptable weights, and a
> range of received weights, then there's a much greater likelihood
> that some or all of the widgets would be acceptable. (018)
Look, I am not arguing that we cannot possibly describe intervals.
Clearly we can, and indeed in a (much) earlier email I gave some CLIF
axioms for the damn things. My point is that in order to even do this,
the ontology must FIRST assume that the numerals used to express the
endpoints of these intervals denote actual numbers, in the usual
mathematical way. And as soon as you allow that, you do at least allow
the conceptual possibility of numerals denoting quantities exactly.
The interval notion DEPENDS UPON the precise notion, it does not
replace it. (019)
> Your ontology can only work with integer quantities and measurement
> instruments calibrated in integers. (020)
Not at all. Why only integers? I can describe intervals with
irrational endpoints, in fact, though I doubt it will be very useful:
[(sqrt 2) (sqrt 3)] (021)
> A difference in weights having value one means the widgets are not
> the widgets you ordered. The scales used must be engineered
> specifically for widgets (since weights in general do not really
> occur in integer gram increments). Now you'll also need a different
> scale for the next shipment, because it contains gadgets, and its
> shipping list specifies them to weigh 5000 milligrams. (022)
This is complete fantasy. But in any case, I doubt if a shipping clerk
is going to be using an ontology. The more likely use would be to
check mutual consistency of shipping regulations between countries,
say, or to figure out the total cargo weight, in tonnes, of an order
expressed using units of bushels of grain. Neither of these involve
anyone doing any actual measurements, only calculations. (023)
Pat (024)
>
> In short, without an ability to express uncertainty, the information
> you pass describing quantities will not be practical for any actual
> use.
>
> R/jbc
> --
> _______________________________
> Joseph B. Collins, Ph.D.
> Code 5583, Adv. Info. Tech.
> Naval Research Laboratory
> Washington, DC 20375
> (202) 404-7041
> (202) 767-1122 (fax)
> B34, R221C
> _______________________________
> (025)
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