[QUANTITY] Data Model for Quantity v0.5 - analogue absurdium

[Brian Thomas]

On Monday 10 May 2004 08:46 am, David Berry wrote:
> That may be just a perception issue. Admittedly the document makes it
> look fairly heavy, and I suspect the models presented by the interface and
> the "first cut"  serialisation examples may appear to lean in different
> directions (although Brian may not agree!), but non-the-less, all the
> quantity model currently covers is how to record meta-data describing the
> phenomenon measured by the Quantity, and the coordinate axes used to
> locate each sampled value.

	I agree with this more or less. The serialization document lays out the
	structure, which is fairly simple. Here's a copy :

--- begin snippet ----

   The components of these types of quantity are given elsewhere, but
   summarized here, are:

        Basic Quantity
                UCD
                CoordSystem
                Units
                DataType
                Value
                Accuracy

        Core Quantity
                UCD
                CoordSystem
                Units
                DataType
                Values
                AltValues
                Accuracy

        Std Quantity
                UCD
                CoordSystem
                Units
                DataType
                AxesList (gives coordinate frames for accessing values in Q)
                Values
                AltValues
                Accuracy

--- end snippet ----


        Each of the components is either fairly simple in structure, or re-uses
	the quantity structure itself (e.g. "accuracy", "altValues", "axesList" and 
	"coordSystem" are conceived as types of quantities, or lists of quantities).

	Now, that wasn't so bad, was it? How these quantities are used, how
	things like "units", "dataType" and "accuracy" are defined are still
	up in the air.

        How the quantities are used within other data models is also up for
	debate. My feeling is that they should be inherited by all node/structures 
	which are going to hold any scientific number/string information. This 
	seems (to me) the only way to truly satisfy the requirement that the data 
	models be universally searchable, transportable and "machine understandable". 
	Others feel that they should be limited to use only for the primary data container
	and then, only in aggregation. 

	=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]