[QUANTITY] doc consistency

[Brian Thomas]

On Friday 14 May 2004 02:44 pm, Jonathan McDowell wrote:
> [snip leading text... proceeding to proposed solution]
>  So when you say "UCD - Optional" and "Units - required, but
>  default is <unitless>", you actually mean:
>
>  UCD:  getUCDString() may return blank or null string to indicate
>  no associated UCD. This is the default if the tag is omitted on
>  serialization.
>
>  Units: getUnit() may return the special Unit value <unitless>.
>  This is the default if the tag is omitted or given a blank value
>  on serialization.
>
>  Do you agree?

	Jonathan, 

	I think you are correct. In the serialization, we may lead things
	out, whereby we are meaning either some default applies
	(dataType == string) =OR= its undefined (ucd == "null"). In the
	interface, we perhaps need to treat this differently as per
	your solution above. 

	I think there needs to be careful choice of the "default" accuracy 
	for Q..I propose the "NoAccuracyDefined" which means that no 
	body cared to supply an accuracy be the default object returned. 
	"AccuracyExact" can be saved for those things which are defined 
	or are constants, for example the speed of light, HTM grid, etc. 

	Perhaps the discussion of default accuracy should be delayed, but
	it does point to the fact that several additional nodes in the serialization
	and simple interfaces for the "default" objects need to be defined.


	=b.t.


-- 

  * Dr. Brian Thomas 

  * Dept of Astronomy/University of Maryland-College Park 
  * Code 630.1/Goddard Space Flight Center-NASA

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  * phone: (301) 286-6128 [GSFC]
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