Abstract: A system and method for defining a process structure for performing a task. The system comprises a computer, having a data storage memory, a keyboard for inputting data and a screen. A user inputs a first process definition which comprises a verb word and an object word defining the task for which a structure is to be created. The user is then able to define subsequent process definitions which are a predicted consequence of executing the first process definition or a predicted constituent step in executing the first process definition. By analyzing each process definition at each stage a complete process structure for performing the task can be built up and refined. The user is also able to specify particular object words falling within the meaning of the object word of a particular process definition which can be called up in tabular form on the screen, overwriting the display of process definitions in the process structure.