A software size estimation model and its evaluation

The authors propose a model for estimating software size based on the program design and other documents, then evaluate the model by looking at some application examples. The model assumes a stepwise evaluation of software size at different levels of program design documents. It accounts for the degree of processing complexity and environmental factors by means of correction factors applied to the raw estimate. For each unit of processing used to realize the various functions making up a program, a reference size is set in advance based on previous results. An estimated program size is then arrived at by totalling the number of processing units derived from the documents. When the estimate is made, an error range is set according to the degree to which functions are analyzed at each level, providing a measure of the accuracy of estimates. (C) 1997 by Elsevier Science Inc.