Modeling and Analysis of Software Aging Process

. This paper proposes a model of successful maintenance that can represent how maintainability of each software module changes as it ages. We found that some of the metrics, measured from 20 years old system, fit our model; i.e., values of those metrics seem to be proportional to the degree of maintainability. We described each metric's critical line -- a value that can be used for deciding whether a module should be re-engineered or not. We also described the interpretations on how each software metric relates to maintainability. 1 Introduction Many organizations have aged software that had been developed many years ago and have been continuously modified and expanded till today[4]. While they are so crucial to organizations' survival, they cannot be retired. However, in order to keep aged software up to date, the maintenance cost tends to increase year by year because "modifying the software" itself makes the software more difficult to be modified. That is, aging software beco..