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For the Pentaho Analysis (legacy) datasource aka Legacy Banded MDX, this is the old way the columns returned prior to Pentaho Report Designer 3.5 and created so that reports migrated easily to 3.5 and beyond. The columns return like this:
Product,
Product{},
Quantity/APAC/Markets,
Quantity/All Markets/Markets,
Quantity/EMEA/Markets,
Quantity/Japan/Markets,
...