Using metrics to evaluate software system maintainability

Software metrics have been much criticized in the last few years, sometimes justly but more often unjustly, because critics misunderstand the intent behind the technology. Software complexity metrics, for example, rarely measure the "inherent complexity" embedded in software systems, but they do a very good job of comparing the relative complexity of one portion of a system with another. In essence, they are good modeling tools. Whether they are also good measuring tools depends on how consistently and appropriately they are applied.>