If you want to create segments for a segmentation group using a new dimension, you need to add a dimension rule to the driving table of the segmentation group. A dimension rule is a WHERE clause fragment that associates the segmentation group driving table with the dimension parameters.

The dimension rule defines the logic used to segment the driving table by that dimension. You can associate one or more dimensions with a segmentation group using dimension rules. The dimensions you associate with a segmentation group define the segmentation criteria.