Constructing software bears many similarities to constructing buildings. In a building project, each floor builds on the previous structures (walls of the previous floors) with some structures being more foundational (i.e. essential) for other structures and some periods of construction being more foundational (i.e. critical) to the final structure. In a software project, each change builds on the structures created by prior changes with some changes creating foundational structure and with some time periods of changes being more foundational than others. This thesis is inspired by this similarity between constructing buildings and constructing software. The thesis makes use of the similarity to study the evolution of software projects. In particular, we develop the concept of time dependence between code changes to study software evolution through empirical studies on two large open source projects (PostgreSQL and FreeBSD) with more than 25 years of development history. We show that time dependence can be used to study how changes build on prior changes and the impact of this building process on the quality of a project. We show how a development period impacts the development of future periods in a project. We also show how a subsystem (module) of a project builds on other subsystems and we identify the subsystems that have high impact on a project's development. Using this knowledge, managers can better monitor the progress of the projects and better plan for future changes. / Thesis (Master, Computing) -- Queen's University, 2010-05-29 11:25:39.005

This thesis focuses on an Agent-Based Service-Oriented approach to evolving legacy system into a Pervasive Computing environment. The methodology consists of multiple phases: using reverse engineering techniques to comprehend and decompose legacy systems, employing XML and Web Services to transform and represent a legacy system as pervasive services, and integrating these pervasive services into pervasive computing environments with agent based integration technology. A legacy intelligent building system is used as a case study for experiments with the approach, which demonstrates that the proposed approach has the ability to evolve legacy systems into pervasive service environments seamlessly. Conclusion is drawn based on analysis and further research directions are also discussed.

High security level must be guaranteed in applications in order to mitigate risks during the deployment of information systems in open network environments. However, a significant number of legacy systems remain in use which poses security risks to the enterprise' assets due to the poor technologies used and lack of security concerns when they were in design. Software reengineering is a way out to improve their security levels in a systematic way. Model driven is an approach in which model as defined by its type directs the execution of the process. The aim of this research is to explore how model driven approach can facilitate the software reengineering driven by security demand. The research in this thesis involves the following three phases. Firstly, legacy system understanding is performed using reverse engineering techniques. Task of this phase is to reverse engineer legacy system into UML models, partition the legacy system into subsystems with the help of model slicing technique and detect existing security mechanisms to determine whether or not the provided security in the legacy system satisfies the user's security objectives. Secondly, security requirements are elicited using risk analysis method. It is the process of analysing key aspects of the legacy systems in terms of security. A new risk assessment method, taking consideration of asset, threat and vulnerability, is proposed and used to elicit the security requirements which will generate the detailed security requirements in the specific format to direct the subsequent security enhancement. Finally, security enhancement for the system is performed using the proposed ontology based security pattern approach. It is the stage that security patterns derived from security expertise and fulfilling the elicited security requirements are selected and integrated in the legacy system models with the help of the proposed security ontology. The proposed approach is evaluated by the selected case study. Based on the analysis, conclusions are drawn and future research is discussed at the end of this thesis. The results show this thesis contributes an effective, reusable and suitable evolution approach for software security.

The dynamic behaviour of a software system changes as a consequence of developer’s static source code modifications. In this thesis, we improve upon a previous approach that combines static and dynamic analyses to categorize behavioural changes by greatly improving its accuracy through polymorphic mapping. We further refine the previous model by introducing a change-centric state transition model that captures the flow of call pairs among different partitions based on static and dynamic call graphs. We also extend the approach by incorporating complete dynamic call stacks into the analysis. Finally, we perform a longitudinal analysis of three software systems to categorize how they have dynamically evolved across 100 program versions. In our evaluation, the polymorphic mapping algorithm decreased mismatches between the static and dynamic analyses by 53%. In particular, we decreased the mismatch by 71% in the most important category of changes from the developer’s point of view. We found that developers introduce new behaviour more often than eliminating old behaviour. Our results show that developers are more likely to remove unexecuted/dead code than code that is executed dynamically. In terms of change types, we found that changes made to fix defects encountered the least inconsistent and unexpected behaviour, while changes made to add new functionality experienced the highest unexecuted behaviour. Finally, we argue that augmenting the dynamic analyses with call stacks provides useful information that helps developers analyze the implications of the call pairs highlighted by our analyses.

The dynamic behaviour of a software system changes as a consequence of developer’s static source code modifications. In this thesis, we improve upon a previous approach that combines static and dynamic analyses to categorize behavioural changes by greatly improving its accuracy through polymorphic mapping. We further refine the previous model by introducing a change-centric state transition model that captures the flow of call pairs among different partitions based on static and dynamic call graphs. We also extend the approach by incorporating complete dynamic call stacks into the analysis. Finally, we perform a longitudinal analysis of three software systems to categorize how they have dynamically evolved across 100 program versions. In our evaluation, the polymorphic mapping algorithm decreased mismatches between the static and dynamic analyses by 53%. In particular, we decreased the mismatch by 71% in the most important category of changes from the developer’s point of view. We found that developers introduce new behaviour more often than eliminating old behaviour. Our results show that developers are more likely to remove unexecuted/dead code than code that is executed dynamically. In terms of change types, we found that changes made to fix defects encountered the least inconsistent and unexpected behaviour, while changes made to add new functionality experienced the highest unexecuted behaviour. Finally, we argue that augmenting the dynamic analyses with call stacks provides useful information that helps developers analyze the implications of the call pairs highlighted by our analyses.

<p> Software Evolution is unavoidable because software systems are subject to continuous change, continuing growth and increasing complexity. As software systems become mission-critical and large in size, the complexity in software development is now focused on software evolution rather than construction. In this work, we view a software system as an entity that is evolving throughout its lifetime, during development and maintenance. Based on a broad survey of software evolution approaches, we propose an architecture-based solution for software evolution, which is defined in terms of evolution specific operations on architectural elements, that is, adding, removing, replacing components and (or) connectors, transforming configurations according to the required changes. In our view of software architectures, connectors are more likely to change since they are the architectural elements which reflect business rules. This work is focused on the evolution of connectors in architectures describing detailed design. Coordination contracts are introduced by Fiadeiro et al. as a realization of connectors at this detailed architecture level, which enables a three-layer architecture to separate concerns of components, connectors and configuration during evolution. Furthermore, to constrain the evolution in a predictable direction, we have established a matching scheme for justifying behavioral relationships between coordination contracts by specification matching based on pre- and postconditions of contracts and methods. A number of specification matches, with various degrees of similarity between the evolved and evolving contracts, have been developed for system behaviors after evolution operations. Case studies are exhibited give a better understanding of these matches.</p> / Thesis / Master of Science (MSc)

The evident progression of ubiquitous technologies has put forward the introduction of new features which software systems can sustain. Several of the ubiquitous technologies available today are regarded as fundamental elements of many software applications in various domains. The utilisation of ubiquitous technologies has an apparent impact on business processes that can grant organisations a competitive advantage and improve their productivity. The change in the business processes in such organisations typically leads to a change in the underlying software systems. In addressing the need for change in the underlying software systems, this research is focused on establishing a general framework and methodology to facilitate the reengineering of software systems in order to allow the incorporation of new features which are introduced by the employment of ubiquitous technologies. Although this thesis aims to be general and not limited to a specific programming language or software development approach, the focus is on Object-Oriented software. The reengineering framework follows a systematic step-based approach, with greater focus on the reverse engineering aspect. The four stages of the framework are: program understanding, additional-requirement engineering, integration, and finally the testing and operation stage. In its first stage, the proposed reengineering framework regards the source code as the starting point to understand the system using a static-analysis based method. The second stage is concerned with the elicitation of the user functional requirements resulting from the introduction of ubiquitous technologies. In the third stage, the goal is to integrate the system’s components and hardware handlers using a developed integration algorithm and available integration techniques. In the fourth and final stage, which is discussed in a general manner only in this thesis, the reengineered system is tested and put in the operation phase. The proposed approach is demonstrated using a case study in Java to show that the proposed approach is feasible and promising in its domain. Conclusions are drawn based on analysis and further research directions are discussed at the end of the study.

Enterprises can be empowered to live up to the potential of becoming dynamic, agile and real-time. Service orientation is emerging from the amalgamation of a number of key business, technology and cultural developments. Three essential trends in particular are coming together to create a new revolutionary breed of enterprise, the service-oriented enterprise (SOE): (1) the continuous performance management of the enterprise; (2) the emergence of business process management; and (3) advances in the standards-based service-oriented infrastructures. This thesis focuses on this emerging three-layered architecture that builds on a service-oriented architecture framework, with a process layer that brings technology and business together, and a corporate performance layer that continually monitors and improves the performance indicators of global enterprises provides a novel framework for the business context in which to apply the important technical idea of service orientation and moves it from being an interesting tool for engineers to a vehicle for business managers to fundamentally improve their businesses.

Today it is more a rule than an exception that software systems have a lifecycle of more than several years. Hence, software evolution is inevitable. During the life span of a software system the domain in which the system is working evolves and changes. This causes changes to the software system, and the software system may also be evolved to satisfy new markets. The ability to evolve gracefully, and thus the long-term success of a software system, is to a large extent governed by its software architecture and the ability of the software architecture to fulfil requirements on quality attributes and to adapt to evolving requirements. In this thesis we study evolution of software architectures and what can be done to support this evolution. We focus on three particular aspects of evolution support: how to ensure that the correct blend of quality attributes is met (architecture selection), the technical means available for supporting changes in the software system (variability), and what types of changes that are likely to occur during evolution (categories of evolution). We introduce a method for architecture evaluation and selection that focus on ensuring that the selected software architecture is the architecture candidate with the most potential for fulfilling a particular blend of quality attributes. The method is based on quantification of expert opinions and focused discussions where these expert opinions differ. The architecture evaluation and selection method is studied in both an academic and in an industry setting. We also introduce a taxonomy of techniques for realising variability in a software system and study how the techniques in this taxonomy are applied in different evolution situations. The taxonomy is based on several industry case studies. Two industry cases are studied in further detail and the evolution of these systems are followed over a number of releases and generations. During this evolution it is shown how variability mechanisms are used to also support evolution, and that there are typical cases of evolution that a software system can be prepared to cope with. The contribution of this thesis is that it increases the understanding of how evolution occurs in a software system, how to create software that is flexible enough to support evolution and how to evaluate and select a software architecture that meets a particular blend of quality attributes. Together this ensures that a software system is based on a software architecture that fits the current quality requirements and that is flexible in the right places so that it is able to evolve gracefully.

Object-oriented systems that undergo repeated modifications commonly endure a loss of quality and design decay. This problem is often remedied by applying refactorings. Refactoring is one of the most important and commonly used techniques to improve the quality of the code by eliminating redundancy and reducing complexity; frequently refactored code is believed to be easier to understand, maintain and test. Object-oriented metrics provide an easy means to extract useful and measurable information about the structure of a software system. Metrics have been used to identify refactoring opportunities, detect refactorings that have previously been applied and gauge quality improvements after the application of refactorings. This thesis provides an in-depth analytical study of the relationship between metrics and refactorings. For this purpose we analyzed 136 versions of 4 different open source projects. We used RefactoringCrawler, an automatic refactoring detection tool to identify refactorings and then analyzed various metrics to study whether metrics can be used to (1) reliably identify refactoring opportunities, (2) detect refactorings that were previously applied, and (3) estimate the impact of refactoring on software quality. In conclusion, our study showed that metrics cannot be reliably used to either identify refactoring opportunities or detect refactorings. It is very difficult to use metrics to estimate the impact of refactoring, however studying the evolution of metrics at a system level indicates that refactoring does improve software quality and reduce complexity. / text