Measuring Software Evolution with Changing Lines of Code

摘要

A standard method for quantitatively measuring the evolution of software and the intellectual property it represents is needed. Traditionally, the evolution of software systems has been subjectively measured by counting the addition of new architectural elements or by comparing source code metrics. An architectural analysis is a subjective measurement technique, as each element must be weighed by importance and difficulty of implementation. This method also requires a complete understanding of the architecture, which is not always readily available. Traditional quantitative source code metrics are designed to evaluate static code, and do not properly capture the dynamic changes of code as it evolves. These hurdles in traditional software analysis necessitate the development of a new quantitative method of evolution measurement. This method would also be useful for measuring the evolution of the intellectual property value of the source code. This paper demonstrates a method for measuring the evolution of source code by analyzing the number of lines of code that have been modified, added, or remain through subsequent versions. This new method of measuring the changing lines of code (CLOC) will be demonstrated by examining the evolution of three major open source projects: the Linux Kernel, Apache HTTP Server and Mozilla Firefox.