Just a quick post about what type of file you should use when modeling Cognos Transformer cubes. I know the old school thinking for Windows based Transformer users was to use PYI or PYJ, but here are some reasons why I think you should use MDL instead.

• The performance gap between cube builds using PY* and MDL has narrowed significantly over the years.
• Ever get a corrupted PY* file? 'nuff said.
• MDL is a pure text format. That makes diff comparison easy when you are using source control or a tool like WinMerge
• MDL files now contain encrypted user information.
• MDL files are cross platform.
• MDL's can be parsed using a tool like Pentaho to create cube model documentation (assuming you have good habits and documented everything within the model).
• Remember the fiasco when Transformer moved to PYJ and you couldn't load a PYI? Well I do.

Just my two cents. Your mileage may vary.