Aruba Networks PowerConnect W Clearpass 100 Software Deployment Manual page 334

Each source field has a name that is unique within the report. You can also attach a description to the field
for use by the report designer. If you select a field from the Data Source Field drop down list, that field
name is automatically placed in the Field Name area. It can be changed if you want.
As derived fields do not exist in the Data Source, you will need to give each field a unique name. You are
also required to give the field a value. This can be by calculating a value using a PHP expression entered in
the Field Expression box.
334 | Report Management ClearPass Guest 3.9 | Deployment Guide