Measuring design diagrams for product quality evaluation

Many important product quality characteristics, such as performance and maintainability, cannot be added on late in the development, and hence early warnings of poor quality expectation would be very useful to allow early corrective measures. To produce such information, we base product quality prediction on measurements and calculations of the UML design diagrams of the software. Some design metrics may be used as direct predictors of quality; as an example, cohesion and coupling metrics are generally considered good predictors of the maintainability of the product. On the other hand, certain quality characteristics, e.g., performance, require more complex analysis of the design by computing predictions of the execution time of a typical use case with user provided information of the input size and attributes. Another way of taking advantage of the design diagrams is by detecting design patterns and anti-patterns in the design, and using these as predictors of the final product quality. While using design patterns is considered to have a positive effect on the quality and productivity of the development process, their effect in product quality is more complex and may in fact be positive or negative, depending on the context. We suggest using the pattern library to store information of the previous uses of the patterns and the quality of the corresponding systems, to predict the quality effects of the design patterns. In our paper, we present a tool for measuring UML diagrams of the product to predict three central product quality characteristics, size, understandability, and performance. The tool also detects all occurrences of a previously defined set of design patterns and antipatterns from the diagrams. Our paper reports industrial experience in using the tool to detect patterns and measure quality of design diagrams.