The Variable Explosion Or how the DDI variable spread out to inhabit multiple modules in DDI 3.0.

The Variable Explosion

Or how the DDI variable spread out to inhabit multiple

modules in DDI 3.0

Once there was a mild mannered DDI 1.0 variable

<var ID="V11" name="V11" catQnty="2"><location StartPos="25" EndPos="25" width="1" RecSegNo="1" fileid="WLT1"/><qstn ID="Q5" seqNo="4"><qstnLit>What country were you born in?</qstnLit></qstn><labl level="var">Nativity</labl><catgry ID="CV11_1"><catValu>1</catValu><labl level="catgry">Native</labl><catStat type=“freq”>798920</catStat></catgry><catgry ID="CV11_2"><catValu>2</catValu><labl level="catgry">Foreign</labl><catStat type=“freq”>210023</catStat></catgry><concept source="archive">Place_of_Birth</concept><derivation><drvdesc>If US code as 1, else code as 2</drvdesc></derivation></var>

It was well contained and kept close to home

<var ID="V11" name="V11" catQnty="2"><location StartPos="25" EndPos="25" width="1" RecSegNo="1“ fileid="WLT1"/><qstn ID="Q5" seqNo="4"><qstnLit>What country were you born in?</qstnLit></qstn><labl level="var">Nativity</labl><catgry ID="CV11_1"><catValu>1</catValu><labl level="catgry">Native</labl><catStat type=“freq”>798920</catStat></catgry><catgry ID="CV11_2"><catValu>2</catValu><labl level="catgry">Foreign</labl><catStat type=“freq”>210023</catStat></catgry><concept source="archive">Place_of_Birth</concept><derivation><drvdesc>If US code as 1, else code as 2</drvdesc></derivation></var>

By 2.1 it has gotten a bit bolder

• You could arrange the variables into nCubes creating multidimensional structures

• It now had an optional place to put data location information

• In allowed for more explicit nesting and category structure

Then along came 3.0 and things got exciting

Modularity ruled!

• Concepts were captured early

• Questions developed and linked to concepts

• Categories were defined…• …and grouped into specific

relationships• Variables were created

using these category groups• Data storage was designed• Physical instances of data

files were created and summary statistics calculated

Fortunately they all hung on to their “handies” and stayed in touch…

Implications for creating documentation• You can create in the order that

information becomes available• You can reuse pieces and imply

relationships• Support community wide concept,

question, category and variable banks• Create new physical instances or

formats without changing other modules

It requires

• Thinking about a variable as a development process rather than as an artifact

• New tools to facilitate information capture and create the appropriate links

Building A Variable

The Variable Explosion Or how the DDI variable spread out to inhabit multiple modules in DDI 3.0.

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