1. A method for building a rule that specifies an action that may occur during execution of an application, the method comprising: storing in a computer memory an expression editor tool; reading, with a processor, an action point definition from a database, the action point definition comprising an action point identifier that specifies an action point located in application program code; determining from the action point definition, with the processor, a dataset that is in-context at the action point in the application program code; executing from the computer memory, with the processor, the expression editor tool, where the expression editor tool is operable to: display an expression definition interface comprising: data source selectors for obtaining selected data fields from among the dataset; and an operator selector for obtaining a selected logical operator to connect the selected data fields; construct a new expression from the selected data fields and the selected logical operator; display an outcome selection interface comprising: an outcome selector for obtaining a selected outcome for the new expression; create a rule comprising the new expression and the selected outcome; and store the rule in the database linked to the action point definition.