Hatley–Pirbhai modeling is a system modeling technique based on the input–process–output model (IPO model), which extends the IPO model by adding user interface processing and maintenance and self-testing processing.[1]
The five components - inputs, outputs, user interface, maintenance, and processing - are added to a system model template to allow for modeling of the system which allows for proper assignment to the processing regions.[1] This modeling technique allows for creation of a hierarchy of detail of which the top level of this hierarchy should consist of a context diagram.[1] The context diagram serves the purpose of "establish[ing] the information boundary between the system being implemented and the environment in which the system is to operate."[1] Further refinement of the context diagram requires analysis of the system designated by the shaded rectangle through the development of a system functional flow block diagram.[1] The flows within the model represent material, energy, data, or information.[2]
. Roger S. Pressman . Software Engineering - A Practitioner's Approach . 1982 . 6th . McGraw-Hill . New York, NY . 2005 . 0-07-285318-2 . 133.