A change impact model for changeability assessment in object-oriented software systems

Growing maintenance costs have become a major concern for developers and users of software systems. Changeability is an important aspect of maintainability, especially in environments where software changes are frequently required. In this work, the assumption that high-level design has an influence on maintainability is carried over to changeability and investigated for that quality characteristics. The approach taken to assess the changeability of an object-oriented (OO) system is to compute the impact of changes made to classes of the system. A change impact model is defined at the conceptual level and mapped on the C++ language. In order to assess the practicality of the model on large industrial software systems, an experiment involving the impact of one change is carried out on a telecommunications system. The results suggest that the software can easily absorb that kind of change and that well chosen conventional OO design metrics can be used as indicators of changeability.