
You need to assign an expression as Top Expression when you choose Functional or Functional and Event mode of operation.
For more information, see Modes of Operation
Creating a BRMS Connector Expression
Creating a Constant Expression
Creating a DB Lookup Expression
Creating a Decision Table Expression
Creating a Decision Tree Expression
Creating a Function Call Expression
Creating a Random Number Expression
Creating a Value Range Expression
Creating a Search Tree Expression
Creating a Static Method Call Expression