Putting Variable Specifications into DDI
Start with existing variable descriptions
- SAS/SPSS/Stata data definitions
- SDA data description files (DDL file)
- Machine-readable codebooks
Transform into DDI
- Use SDA 'xconvert' program for SAS/SPSS/Stata
- Use SDA 'ddltox' program for SDA DDL files
- Nesstar utilities for some applications
- Write a program or a Perl script, if necessary
Add missing elements
- SAS/SPSS/Stata lack text of questions
- Statistics, if desired
- We will need a program to merge information into DDI files
Note that some software applications will generate DDI files
(eventually)
- CASES and Blaise, in newer versions
- SDA 'subset' procedure
- SDA 'sdatoxml' program (with statistics)
- Nesstar, for its system files
Example