[DDI-SRG] Map 2.1 to 3.0

[Wendy Thomas]

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