The dimension of time in software appears in both program execution and software evolution. Much research has been devoted to the understanding of either program execution or software evolution, but these two research communities have developed tools and solutions exclusively in their respective context. In this paper, we claim that a common comprehension framework should apply to the time dimension of software. We formalize this as a meta-model that we instantiate and apply to the two different comprehension problems.

Software evolution history is usually represented at fine granularity by commits in software repositories, and at coarse granularity by software releases. In order to gain insights on development activities and on software evolution, the information on releases is too general, whereas the information on commits is prohibitively large to be efficiently processed by a developer. This paper proposes an automatic technique for the identification of distinct phases of evolution. Such software evolution phases are characterized by similar development activities in terms of changes to entities. Therefore, our technique decomposes software evolution history to assist developers identify periods of different development activities. Our analysis technique is a search-based optimization of the best decomposition of commits from the software repository using heuristics such as classes changed in each commit, and the magnitude/importance of these changes. To validate our technique, we applied it on the evolution history of five case studies covering multiple releases over several years of development. An interesting outcome of the evaluation is that our automatic decomposition of software evolution history recovered the original decomposition in software releases.

Learning to use existing or new software libraries is a difficult task for software developers, which would impede their productivity. Much existing work has provided different techniques to mine API usage patterns from client programs in order to help developers on understanding and using existing libraries. However, considering only client programs to identify API usage patterns is a strong constraint as the client programs source code is not always available or the clients themselves do not exist yet for newly released APIs. In this paper, we propose a technique for mining Non Client-based Usage Patterns (NCBUP miner). We detect unordered API usage patterns as distinct groups of API methods that are structurally and semantically related and thus may contribute together to the implementation of a particular functionality for potential client programs. We evaluated our technique through four APIs. The obtained results are comparable to those of client-based approaches in terms of usage-patterns cohesion.

Mobile apps are becoming complex software systems that must be developed quickly and evolve continuously to fit new user requirements and execution contexts. However, addressing these requirements may result in poor design choices, also known as antipatterns, which may incidentally degrade software quality and performance. Thus, the automatic detection and tracking of antipatterns in this apps are important activities in order to ease both maintenance and evolution. Moreover, they guide developers to refactor their applications and thus, to improve their quality. While antipatterns are well-known in object-oriented applications, their study in mobile applications is still in its infancy. In this paper, we analyze the evolution of mobile apps quality on 3, 568 versions of 106 popular Android applications downloaded from the Google Play Store. For this purpose, we use a tooled approach, called PAPRIKA, to identify 3 object-oriented and 4 Android-specific antipatterns from binaries of mobile apps, and to analyze their quality along evolutions.

Learning to use existing or new software libraries is a difficult task for software developers, which would impede their productivity. Most of existing work provided different techniques to mine API usage patterns from client programs, in order to help developers to understand and use existing libraries. However, considering only client programs to identify API usage patterns, is a strong constraint as collecting several similar client programs for an API is not a trivial task. And even if these clients are available, all the usage scenarios of the API of interest may not be covered by those clients. In this paper, we propose a visualization based approach for the refinement of Client-based Usage Patterns. We first visualize the patterns structure. Then we enrich the patterns with API methods that are semantically related to them, and thus may contribute together to the implementation of a particular functionality for potential client programs.

Software developers need to cope with complexity of Application Programming Interfaces (APIs) of external libraries or frameworks. However, typical APIs provide several thousands of methods to their client programs, and such large APIs are difficult to learn and use. An API method is generally used within client programs along with other methods of the API of interest. Despite this, co-usage relationships between API methods are often not documented. We propose a technique for mining Multi-Level API Usage Patterns (MLUP) to exhibit the co-usage relationships between methods of the API of interest across interfering usage scenarios. We detect multi-level usage patterns as distinct groups of API methods, where each group is uniformly used across variable client programs, independently of usage contexts. We evaluated our technique through the usage of four APIs having up to 22 client programs per API. For all the studied APIs, our technique was able to detect usage patterns that are, almost all, highly consistent and highly cohesive across a considerable variability of client programs.

Software visualization as a research field focuses on the visualization of the structure, behavior, and evolution of software. It studies techniques and methods for graphically representing these different aspects of software. Interest in software visualization has grown in recent years, producing rapid advances in the diversity of research and in the scope of proposed techniques, and aiding the application experts who use these techniques to advance their own research. Despite the importance of evaluating software visualization research, there is little work studying validation methods. As a consequence, it is usually difficult producing compelling evidence about the effectiveness of software visualization contributions. The goal of this paper is to study the validation techniques performed in the software visualization literature. We conducted a systematic mapping study of validation methods in software visualization. We consider 752 articles from multiple sources, published between 2000 and 2012, and study the validation techniques of the software visualization articles. The main outcome of this study is the lack in rigor when validating software visualization tool and techniques. Although software visualization has grown in interest in the last decade, it still lacks the necessary maturity to be properly and thoroughly evaluating its claims. Most article evaluations studied in this paper are qualitative case studies, including discussions about the benefits of the proposed visualizations. The results help understand the needs in software visualization validation techniques. They identify the type of evaluations that should be performed to address this deficiency. The specific analysis of SOFTVIS series articles shows that the specialized conference suffers from the same shortage.

Interactive software visualization offers a promising support for program comprehension, including program dynamicity. We present, the extension of an existing visualization tool with heat maps to explore the time and other dimensions of software. To this end, we first propose a framework to unify the two main software dynamicities, execution and evolution. Then, this unified framework is exploited to define a visualization environment based on heat maps. We illustrate our approach on two comprehension tasks: understanding the behavior of programmers during the evolution of an application and understanding class contributions in use cases. The case studies show that the heat-map metaphor contributes to answer, more easily, many of the questions important to program comprehension.