An operator interface within a process plant includes an execution engine that implements process flow modules made up of interconnected smart process objects that are aware of devices and other entities within the plant and that can perform methods to detect conditions within the plant, especially on a system-level basis. The smart process objects include a display element to be displayed to the operator, data storage for storing data pertaining to and/or received from an associated entity within a plant, inputs and outputs for communicating with other smart process objects and methods that may be executed on the stored and received data to detect plant conditions, including system-level conditions, such as leaks, errors and other conditions. Process flow modules, which may be made up of numerous interconnected smart process objects, may also include flow algorithms associated therewith to calculate mass balances, flows, etc. for the process elements within the process flow modules.