Applying and Interpreting Object Oriented Metrics

Object-oriented design and development is becoming very popular in today's software development environment. Object oriented development requires not only a different approach to design and implementation, it requires a different approach to software metrics. Since object oriented technology uses objects and not algorithms as its fundamental building blocks, the approach to software metrics for object oriented programs must be different from the standard metrics set. Some metrics, such as lines of code and cyclomatic complexity, have become accepted as "standard" for traditional functional/ procedural programs, but for objectoriented, there are many proposed object oriented metrics in the literature. The question is, "Which object oriented metrics should a project use, and can any of the traditional metrics be adapted to the object oriented environment?" In this paper, the Software Assurance Technology Center (SATC) at NASA Goddard Space Flight Center discusses its approach to choosing metrics for a project by first identifying the attributes associated with object oriented development. Within this framework, nine metrics for object oriented are selected. These metrics include three traditional metrics adapted for an object oriented environment, and six "new" metrics to evaluate the principle object oriented structures and concepts. The metrics are first defined, then using a very simplistic object oriented example, the metrics are applied. Interpretation guidelines are then discussed and data from NASA projects are used to demonstrate the application of the metrics. In the experience of the SATC, projects choose the data they collect by default if the tool they are using compiles it, the project collects it. The purpose of this paper is to help project managers choose a comprehensive set of metrics, not by default, but by using a set of metrics based on attributes and features of object oriented technology. Applying and Interpreting Object Oriented Metrics