What can violations of good practices tell about the relationship between GoF patterns and run-time quality attributes?

Context GoF patterns have been extensively studied with respect to the benefit they provide as problem-solving, communication and quality improvement mechanisms. The latter has been mostly investigated through empirical studies, but some aspects of quality (esp. run-time ones) are still under-investigated. Objective In this paper, we study if the presence of patterns enforces the conformance to good coding practices. To achieve this goal, we explore the relationship between the presence of GoF design patterns and violations of good practices related to source code correctness, performance and security, via static analysis. Method Specifically, we exploit static analysis so as to investigate whether the number of violations of good coding practices identified on classes is related to: (a) their participation in pattern occurrences, (b) the pattern category, (c) the pattern in which they participate, and (d) their role within the pattern occurrence. To answer these questions, we performed a case study on approximately 13,000 classes retrieved from five open-source projects. Results The obtained results suggest that classes not participating in patterns are more probable to violate good coding practices for correctness, performance and security. In a more fine-grained level of analysis, by focusing on specific patterns, we observed that patterns with more complex structure (e.g., Decorator) and pattern roles that are more change-prone (e.g., Subclasses) are more likely to be associated with a higher number of violations (up to 50 times more violations). Conclusion This finding implies that investing in a well-thought architecture based on best practices, such as patterns, is often accompanied with cleaner code with fewer violations

Applying patterns in embedded systems design for managing quality attributes and their trade-offs

Embedded systems comprise one of the most important types of software-intensive systems, as they are pervasive and used in daily life more than any other type, e.g., in cars or in electrical appliances. When these systems operate under hard constraints, the violation of which can lead to catastrophic events, the system is classified as a critical embedded system (CES). The quality attributes related to these hard constraints are named critical quality attributes (CQAs). For example, the performance of the software for cruise-control or self-driving in a car are critical as they can potentially relate to harming human lives. Despite the growing body of knowledge on engineering CESs, there is still a lack of approaches that can support its design, while managing CQAs and their trade-offs with noncritical ones (e.g., maintainability and reusability). To address this gap, the state-of-research and practice on designing CES and managing quality trade-offs were explored, approaches to improve its design identified, and the merit of these approaches empirically investigated. When designing software, one common approach is to organize its components according to well-known structures, named design patterns. However, these patterns may be avoided in some classes of systems such as CES, as they are sometimes associated with the detriment of CQAs. In short, the findings reported in the thesis suggest that, when applicable, design patterns can promote CQAs while supporting the management of trade-offs. The thesis also reports on a phenomena, namely pattern grime, and factors that can influence the extent of the observed benefits