Before revision: A sample system context diagram using Hatley-Pirbhai Modeling Hatley-Pirbhai modeling is a system modeling technique based on the input-processing-output model (IPO model), which extends the IPO model by adding user interface processing and maintenance and self-testing processing.
After revision: A sample system context diagram using Hatley–Pirbhai modeling Hatley–Pirbhai modeling is a system modeling technique based on the input–processing–output model (IPO model), which extends the IPO model by adding user interface processing and maintenance and self-testing processing.