Global Variables in Custom Activities
The custom activity may rely on global variables for user-specified information, such as database connection information or JMS topic names. When a user places a custom activity within a process definition, any global variables used by the process referenced in the custom activity that are not already defined in the project are placed in the global variable list of the project.
You should document any global variables required by a custom activity so that users of the activity can specify an appropriate value for each global variable.