[QUANTITY] Requirements and apology

[Ed Shaya]

Dave,

David Berry wrote:

>Ed,
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>>Astronomers rarely query for a single number.
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>Do you mean a single number, or a single quantity? 
>
number

>I read Ray's
>message as implying that a Quantity can contain multiple values,
>not just a single value. [He didn't say this explicitly but it is
>implicit in his use of plurals in statements such as "It is *not* a
>requirement that the values that make up the quantity may have
>different units."]
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I read Ray's values as only allowing a vector (as in the math sense of 
an arrow that requires multiple components to describe it).  Hopefully, 
Ray will clarify.

>>Not only is it inefficient to create many small objects, but
>>one immediately desires a new class that can keep track of what is
>>different about each of the individual atomicQuantities.
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>Why is this? There are two ways in which you can keep track of
>the differences between two of Ray's Quantities without needing
>sub-classes; firstly by including a UCD (or some such thing) as a
>component of the Quantity [this would be a way of implementing Ray's
>item 10: "It should be possible to associate a quantity with the
>physical phenomenon it measures. This association is not required to
>appear in model instances."]; secondly, by the context in which the
>Quantity is used - if a quantity was used as a component of a higher
>level object, it's place within the higher level structure could
>determine the content of the Quantity.
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What I meant was that a list of atomic quantities (all of the same 
property) needs
another list explaining why each number is different, eg. because it is 
the property of
a different object or at a different position.  A list of atomic 
quantities always becomes
a dependent variable in need of an independent variable.  Thus, an array 
quantity should include  Arguments that are quantities, or when the 
quantity is an independent
variable, the Argument is a simple index.

>
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>David
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