Metric, dimension, and filter expressions can use identifiers to refer to named metrics, dimensions, and filters.
These identifiers are case sensitive and must be typed exactly as they are defined.
A valid identifier can contain one or more of the following:
All other characters are illegal in an identifier.
These same rules apply to the names of metrics, dimensions, and filters when they are used outside of expressions, except that the names can contain spaces but not underscores. For example, you can define the Session Referrer dimension in the Transformation.cfg file as Session Referrer, but not Session_Referrer.