[DDI-users] Variable representation: measurementUnit, WeightVariableReference, StandardWeightReference

[Wendy Thomas]

My,

Currently anywhere there is a language option for a string it is 
repeatable to represent different languages. In the next version we will 
add a feature that allows bundling of multiple language representations of 
the same content so many of those 0..n options will go away.

The generic element r:NameType has the following definition:

A reusable type assigned to an element with the naming convention XxxName 
e.g. OrganizationName at selected locations where the element may be 
assumed to be administered by a registry or is otherwise shared. This is a 
human understandable name (word, phrase, or mnemonic) that reflects the 
ISO/IEC 11170-5 naming principles. A name for an element is specified 
within a particular context such as an element administered within a 
registry. When multiple names are used the preferred name should be 
identified by setting the Boolean attribute @isPreferred to 'true'. When 
elements are administered through a registry a Name is required. Names 
within an administered registry should follow the naming conventions of 
the registry. See ISO/IEC 11179-5 Information Technology - Metadata 
Registries (MDR) Part 5: naming and identification principles. 
ISO/IEC1179-5:2005(E). Mnemonics associated with an element should 
included here.

The xxxName is NOT the unique identifer, that is the agency/ID/version as 
expressed in a DDI URN.

Other answers below...

On Wed, 2 Feb 2011, My Coyne wrote:

> Hello,
>
> I am learning about Variable:
> -- A variable associates with 0..* QuestionReference
> -- A variable associates with 0..* VariableName (really?)
> -- A variable associates with 0..1 Representation
>          * A representation has measurementUnit
>          * A representation associates with 0..* WeightVariableReference
>          * A representation associates with 0..* StandardWeightReference
>
> My questions:
> (1)  Under what circumstance a variable will have more than one names?  Furthermore, how does an entity queries the information would know
> which variable name to use?
>       This leads to another question:  If in question q1, the variable name is V1; but in question qn, the variable name is Vn.  How to indicate
> such "order" with QuestionReference and VariableName.  Because it seems that in such case the QuestionReference and VariableName is
> "tightly coupled" and I don't know how the schema can enforce this.
>
See above but basically, language differences is the primary reason for 
repetition. The attribute isPrimary set to true indicates the preferred 
name if multiples occur. In addition a reference to the variable can 
request a preferred language if it is available.

There is no coupling of questions and variables via "name" unless the user 
makes that coupling. In older versions of DDI (1 and 2) everything was 
bundled into the variable causing the problems you noted above. In DDI 3 
questions are listed separately as QuestionItems in a QuestionScheme. If 
managed in a registry they would normally each have a name. When creating 
a survey or other progressive data capture, ControlConstructs are used to 
designate question flow and reference Questions in the appropriate order 
(including IfThenElse, Loop, Repeat, etc.) as needed. A Variable may be 
the direct response to a question, a recoded response, a derivation based 
on multiple questions, or from another source entirely. The question 
reference simply allows you to identify one or more questions that 
resulted in the content of the variable. Coding Instruction Reference 
links to the exact process that resulted in the variable. For example if 
Q1 is part of a loop that is asked of every member of a household and each 
pass through the loop results in V1a, V1b, V1c etc. then the coding 
instruction would indicate a difference value (reflecting the looping 
pass) in order to link the right variable to the right case. We are adding 
the ability to reference Question Constructs (the use of a question in a 
specific location of a question flow) in DDI 3.2.


> (2) What is WeightVariableReference and StandardWeightReference?  why are they not just as simple as a string value of the measurementUnit?
>
Some data files have overall weights assigned such as a strict 10% sample 
of something. This value is described in ProcessingEvent. You would 
include a Weighting (a general description of the weighting process) and a 
Coding/StandardWeight which in this case would contain "10" as the 
weighting factor to by used by the variable. StandardWeightReference is 
repeatable to support highly complex studies that result in the use of 
multiple standard weighting factors for a single variable, sometimes 
depending on the analysis being done.

In other cases where certain groups are oversampled in order to obtain 
sufficient cases for study, a Variable containing a weighting factor is 
included in the data set. The US Public Use Microsamples are an example of 
this. In this case the variable would point to the appropriate Weight 
Variable(s). In complex studies multiple weights are available depending 
on the variable and the specific purpose of the analysis. The description 
of the weight variables themselves should provide guidence in their 
appropriate application.

The measurement unit is simply the unit of measure...$, pound, years, etc.

Wendy

> Thank you for your help.
>
> My Coyne
> mcoyne at boninc.com
> (cel): 301-399-6351
>
>
>
>
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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