With PPM 10.1 the new VARIANTDIM dimension type has been introduced.
Variants classify process instances according to their structure. The relevant structure is the sequence of functions in a process instance. Variant has two dimension levels, Combined variant (rough step width) and Precise variant (refined step width), and the Name as dimension value.
More basic information about variants, a list with affected functionalities, and how to add the variant feature to PPM can be found in the documentation PPM Customizing Toolkit.