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Re: On Quantity - Measurement relationship
- From: Martin Desruisseaux <
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- To:
- Subject: Re: On Quantity - Measurement relationship
- Date: Sat, 01 Nov 2014 18:32:57 +0900
- Organization: Geomatys
Hello Jean-Marie
I agree that a vector is not a quantity. It was indeed my point in my
previous email: a vector could not fit in a hierarchy where Quantity
extends Measurement. It was my argument for keeping the current
hierarchy, so a Vector can extends a Measurement without extending a
Quantity.
Martin
Le 01/11/14 17:19, Jean-Marie Dautelle a écrit :
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Hi Martin and All,
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A scalar is a physical quantity that it represented by a dimensional
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number at a particular point in space and time. Examples are
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hydrostatic pressure and temperature.
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A vector is a bookkeeping tool to keep track of two pieces of
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information (typically magnitude and direction) for a physical quantity.
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From this reference book definition we see that a vector is not a
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quantity (only its magnitude is). Therefore to respond to Martin (and
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what should be written in the spec) is that a Vector/Tensor does not
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belongs to this hierarchy and they are aggregate of quantities or
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aggregate of one quantity with something else (direction)
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A possible choice to enforce this notion of "magnitude" for measured
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quantity would be to replace the name Measurement with Amount !
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I hope this help.
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Jean-Marie.