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Re: On Quantity - Measurement relationship
- From: Werner Keil <
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- To: "
" <
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- Subject: Re: On Quantity - Measurement relationship
- Date: Sat, 1 Nov 2014 16:58:53 +0100
It contains the circular reference where Measurement<Q extends Quantity<Q>>
refers to something that inherits from it[?]
On Sat, Nov 1, 2014 at 4:54 PM, Martin Desruisseaux <
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wrote:
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Le 02/11/14 00:37, Werner Keil a écrit :
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That's part of the Spec, while some terms there (OK, "Measurable" was
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already purged[?]) may be influenced by JSR 275 or the prior Unit-API
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Okay, there is a copy and paste of our spec (emphasis are mine):
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*Quantity:* Any type of *quantitative* property or attribute of a thing.
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For example, 'temperature', 'volume', 'pressure', 'molecular mass' and
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'internal energy' are quantitative properties which can be used to describe
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the state of a confined gas. A unit is not needed to express a quantity.
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For example, Alice can quantify the mass of her shoe by handling it. A unit
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is not needed to do quantitative arithmetic, either. Alice can add the
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mass of her left shoe and the mass of her right shoe by placing them both
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in the pan of a balance. Units are needed to represent measurable
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quantities in a computer, on paper, on a network, etc. *In this API,
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quantities are restricted to the measurable ones: only the quantities that
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can be expressed as the combination of a numerical value and a unit are
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supported.* This is sometime considered as a partial definition of
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Measure rather than Quantity. Nevertheless this API uses the “quantity”
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term for consistency with usage in other frameworks, because the concept of
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quantity is needed anyway for units parametrization, and for avoiding the
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introduction of both concepts in the library.
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I agree with the current spec definition. To me, the Quantity type in
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JSR-363 is a *quantitative measurement*, not a quantity in the sense that
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Jean-Marie said (Jean-Marie point of view is totally valid, but the
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specification approach is more specialized).
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So I think that the current hierarchy is conform to the spec.
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Martin
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