[DDI-SRG] Map 2.1 to 3.0

[Pascal Heus]

Wendy:
This may be worth further discussion. See my last note in bug
http://mantis.ddialliance.org/view.php?id=106
*P

Wendy Thomas wrote:
> Interval
>
> Interval as used in DDI 2.1 was an indication of whether the variable was 
> discrete or continuous. This could be in relationship to a numeric value 
> or a coded value. In DDI 3.O the NumericRepresentation provides much more 
> detailed NumericCodeType that indicates that a the value is a an integer 
> (thus removing the continuous intervening values) and optionally provides 
> an incremental value so that one could provide a step increase of greater 
> than one for an integer NumericDataType or a .5 or other value for a real 
> number. For CodeScheme values the description of Level provides a 
> relationship type (nominal, ordinal, interval) and an optional Interval to 
> provide the actual interval between values of the categories.
>
> Therefore the proper mapping of 2.1 to 3.0 is dependent upon whether the 
> variable has a numeric or codescheme representation.
>
> IF NUMERIC:
>
> intvl maps to Variable/NumericRepresentation/NumericDataType where 
> discrete = integer and continuous = real with the option of providing the 
> exact interval step in interval
>
> IF CODESCHEME:
>
> intvl maps to CodeScheme/Level/RelationshipType = interval and a 
> description of the interval between the values of the categories (however 
> the codeScheme provides the only valid values for the code)
>
>
> The issue with DDI 2.1 is that intvrl has a default value of discrete 
> whether or not it made sense (in other words an open text variable would 
> have an interval value of discrete).
>
> The mapping will will be changed to reflect the complexity of this 
> translation.
>
> Wendy
>
> Wendy L. Thomas                          Phone: +1 612.624.4389
> Data Access Core Director		 Fax:   +1 612.626.8375
> Minnesota Population Center              Email: wlt at pop.umn.edu
> University of Minnesota
> 50 Willey Hall
> 225 19th Avenue South
> Minneapolis, MN 55455
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