Explainations of interface/serializations (what is required) (Was: Re: [QUANTITY] Data Model for Quantity v0.5

[Brian Thomas]

	Hi Pierre,

	Hmm. I guess a few more clarifications are needed...

On Monday 10 May 2004 01:10 pm, Pierre Didelon wrote:
> Brian Thomas wrote:
> > [snip]

 	Hi Pierre,

>
> >>  	Finally, at which level is the accuracy related?
> >
> > 	As I said above, the BQ should allow accuracy.
>
> Beurk! Why?

	Its not a scientific number without an accuracy (unless its 
	a "constant"). It would seem to me that you have to allow
	the user the option to record the errors (!)

> If some people want accuracy let them use CoreQ,
> and let people who don't need accuracy use BasicQ.
> But OK, as you show below accuracy is optionnal so...
> up to DM-Quantity core group decision.

	Correct. This is more a political/scientific rather than technical
	question. 

> [snip]
> OK, I will take a stab at
>
> > 	a summary:
> >
> >          Basic Quantity [id attribute optional]
> >                  UCD  -   Optional
> >                  CoordSystem - Optional
> >                  Units - Optional (Defaults to "unitless")
> >                  DataType - Optional (Defaults to "string of arbitrary
> > length") Value - Required
> >                  Accuracy - Optional
>
> so the minimum Quantity can have only a value (even without UCD),
> with additional info "from" frame; name and description (required or
> optional?)

	Even the frame information (which is essentially "coordSystem" + "axes";
	the latter only occurring in the higher level standardQ) is Optional. 

	Yes, I missed some attributes. Sorry for that, here's the remainder :
	Name and description are for human readability and are optional.
	Size (at this time) is also optional.
	
>
> >          Core Quantity [id, size attributes optional]
> >                  UCD - Optional
> >                  CoordSystem - Optional
> >                  Units - Required (But if absent in serialization it
> > defaults to "unitless") DataType - Required (But if absent in
> > serialization it defaults to "string of arbitrary length") Values -
> > Required
> >                  Accuracy - Optional
> >
> >          Std Quantity [id, size attributes optional]
> >                  UCD - Optional
> >                  CoordSystem - Optional
> >                  Units - Required (But if absent in serialization it
> > defaults to "unitless") DataType - Required (But if absent in
> > serialization it defaults to "string of arbitrary length") AxesList
> > (gives coordinate frames for accessing values in Q) - Optional Values -
> > Required
> >                  AltValues - Optional
> >                  Accuracy - Optional
> >
> >
> >    	So you can see that "dataType", "units" and "values" are required at
> > all levels.
>
> So make it more clear by stabbing it with :
> Required (But if absent in serialization it defaults to "unitless")
> even for BasicQ, isn't it better?

	Yes it is better, and that's what I meant to say but my cut n pasting of text
	didn't go back far enough. Yes, the BasicQuantity should read:

          Basic Quantity [id attribute optional]
                  UCD  -   Optional
                  CoordSystem - Optional
                  Units - Required (But if absent in serialization it defaults to "unitless")
                  DataType - Required (But if absent in serialization it defaults to "string of arbitrary length")
                  Value - Required
                  Accuracy - Optional

> What is the diff. defining interfaces?
> But for the first 2 types of information, we allow for sensible defaults,

	It was a mistake in my email. In terms of datatype, units and value(s) : these
	components are the same for required, and defaults in all interfaces/serializations.

>[snip]
> > 	Did that explanation help?
>
> yes, at least for my understanding,
> but may be not completly for agreement yet ;-)
> thanks.

	Well, a step in the right direction regardless :)

	=-b.t.

>
> > 	Regards,
> >
> > 	=b.t.

-- 

  * Dr. Brian Thomas 

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

  *   fax: (301) 286-1775
  * phone: (301) 286-6128 [GSFC]
           (301) 405-2312 [UMD]