Fault Density, Fault Depth and Fault Multiplicity: The Reward of Discernment

Using a semantics-based definition of faults, we discuss three distinct but related concepts, and illustrate their differences by means of simple experiments: fault density (number of faults in a program); fault depth (the minimal number of fault removals needed to make a program correct); and fault multiplicity (the number of atomic changes needed to repair a single fault).