Value Mappings - Controllers
Here you can select the source and destination mapping controllers.
Source
From the drop-down list choose the type of controller.
Impact COM Controller
Impact Project Database Controller
Impact Project Variable Controller
Impact System Function Controller
Properties
This button will be available if Impact COM Controller has been chosen.
Destination
From the drop-down list choose the type of controller.
<None>
Impact COM Controller
Impact Project Database Controller
Impact Project Variable Controller
Properties
This button will be available if Impact COM Controller has been chosen.
Enable for Impact
Switch this option on if you want this Value Mapping to be executed from Impact.
Enable for nServer
Switch this option on if you want this Value Mapping to be executed from nServer.
Value Mappings - Mappings
From this page you can add new value mappings, modify or delete existing ones.
Value mappings can be assigned for each of the following groups:
Project Mappings - These mappings will be performed once for the current project
All Layer Mappings - These mappings will be performed once for every project layer
Current Layer Mappings - These mappings will be performed once for the current layer
Layer types (one entry for each defined layer type) - These mappings will be performed once for every layer of this type
New Mapping
Press this button to define a new mapping for the highlighted group.
New Clear Value
Press this button to define a new mapping that will clear the value of the specified variable. (This option is only available if the source is either an Impact Project Database Controller or an Impact Project Variable Controller.)
Arrows 
Use the arrows to alter the order of the defined value mappings.
Delete 
Press this button to delete the current value mapping.
Delete All
Press this button to delete all value mappings.
Properties 
Press this button to modify the current value mapping.