Assessment of software system evolvability

The evolvability, the ease of further development, of a software systems is difficult to assess, but may have large economic consequences. Many studies have investigated the relations between particular software metrics and effort on evolving individual classes, but little attention has been given to methods for assessing and measuring evolvability of complete software systems. This paper discusses such methods, and motivates that they should use a combination of structural code measures and expert assessments. This is exemplified in a case study assessing the evolvability of four functionally equivalent systems. The paper also gives with directions for future work on evolvability assessments.