Structured Review of the Evidence for Effects of Code Duplication on Software Quality

This report presents the detailed steps and results of a structured review of code clone literature. The aim of the review is to investigate the evidence for the claim that code duplication has a negative effect on code changeability. This report contains only the details of the review for which there is not enough place to include them in the companion paper published at a conference (Hordijk, Ponisio et al. 2009 - Harmfulness of Code Duplication - A Structured Review of the Evidence)

Panorama - a software maintenance tool

Much of the effort in software maintenance is spent on finding relevant information and on program comprehension. Of the several challenges encountered during this process, some are: a) inadequate documentation, b) the developer doing the maintenance activity may not be the one who actually developed it and may be unfamiliar with the application domain (in addition to the unfamiliar code), c) information overload, and d) the relevant code may be scattered across multiple files of different types making it harder to find. Existing documentation in the form of Javadoc is inadequate in providing a global view of the working of the software. Panorama, a java based Eclipse plug-in, was developed to facilitate maintenance activities by providing mechanisms to document and to view expert knowledge and relevant code in the form of a concern. Some features of Panorama are: a code tracing feature that allows the expert to quickly find (so he can document it) lines of code executed in carrying out a function, a concern management feature that allows the expert to create and organize concern information in a hierarchical manner, a concern visualization and context management feature that helps the maintainer to handle information overload by allowing him to switch between contexts, an enhanced user-interface that helps the maintainer to easily navigate between relevant contexts and codes. Panorama also provides a Javadoc -like documentation of cross-cutting concerns that supplement existing Javadoc documentation to provide comprehensive information about the software. In a case study done to validate the usefulness of our tool, Panorama was used to document the SAVER software (a VB.NET based fairly large GIS software with 26,704 executable lines of code that is being actively used by the Iowa Department of Transportation to analyze automobile crashes over a period of time). SAVER has been undergoing continual bug-fixes and enhancement activities - and preliminary studies indicate that the supplementary documentation provided by Panorama has proven beneficial

A Hybrid Model for Object-Oriented Software Maintenance

An object-oriented software system is composed of a collection of communicating objects that co-operate with one another to achieve some desired goals. The object is the basic unit of abstraction in an OO program; objects may model real-world entities or internal abstractions of the system. Similar objects forms classes, which encapsulate the data and operations performed on the data. Therefore, extracting, analyzing, and modelling classes/objects and their relationships is of key importance in understanding and maintaining object-oriented software systems. However, when dealing with large and complex object-oriented systems, maintainers can easily be overwhelmed by the vast number of classes/objects and the high degree of interdependencies among them. In this thesis, we propose a new model, which we call the Hybrid Model, to represent object-oriented systems at a coarse-grained level of abstraction. To promote the comprehensibility of objects as independent units, we group the complete static description of software objects into aggregate components. Each aggregate component logically represents a set of objects, and the components interact with one other through explicitly defined ports. We present and discuss several applications of the Hybrid Model in reverse engineering and software evolution. The Hybrid Model can be used to support a divide-and-conquer comprehension strategy for program comprehension. At a low level of abstraction, maintainers can focus on one aggregate-component at a time, while at a higher level, each aggregate component can be understood as a whole and be mapped to coarse-grained design abstractions, such as subsystems. Based on the new model, we further propose a set of dependency analysis methods. The analysis results reveal the external properties of aggregate components, and lead to better understand the nature of their interdependencies. In addition, we apply the new model in software evolution analysis. We identify a collection of change patterns in terms of changes in aggregate components and their interrelationships. These patterns help to interpret how an evolving system changes at the architectural level, and provides valuable information to understand why the system is designed as the way it is

A review of software change impact analysis

Change impact analysis is required for constantly evolving systems to support the comprehension, implementation, and evaluation of changes. A lot of research effort has been spent on this subject over the last twenty years, and many approaches were published likewise. However, there has not been an extensive attempt made to summarize and review published approaches as a base for further research in the area. Therefore, we present the results of a comprehensive investigation of software change impact analysis, which is based on a literature review and a taxonomy for impact analysis. The contribution of this review is threefold. First, approaches proposed for impact analysis are explained regarding their motivation and methodology. They are further classified according to the criteria of the taxonomy to enable the comparison and evaluation of approaches proposed in literature. We perform an evaluation of our taxonomy regarding the coverage of its classification criteria in studied literature, which is the second contribution. Last, we address and discuss yet unsolved problems, research areas, and challenges of impact analysis, which were discovered by our review to illustrate possible directions for further research

Interuniversitäres Doktorandenseminar Wirtschaftsinformatik unter Beteiligung der Universitäten Freiberg, Halle, Leipzig, Jena, Dresden und Chemnitz an der TU Bergakademie Freiberg; Dezember 2010

Die internationale Beachtung der Forschungsergebnisse in der Wirtschaftsinformatik hat in den letzten Jahren an Bedeutung gewonnen. Dabei wird dem kritischen Diskurs ein wachsender Stellenwert eingeräumt. Hier gilt es, den wissenschaftlichen Nachwuchs in der Konzeption und Durchführung der eigenen Forschung und den anzuwendenden Forschungsmethoden eine Lern- und Diskussionsplattform zu bieten, um sich der wissenschaftlichen Aussprache zum jeweiligen Gestaltungs- und Erkenntnisziel zu stellen. Um den Dialog zwischen Wirtschaftsinformatikern unterschiedlicher Schwerpunkte zu fördern, veranstalten die mitteldeutschen Wirtschaftsinformatikprofessuren der Universitäten Chemnitz, Dresden, Freiberg, Halle, Jena und Leipzig semesterweise eine Doktorandenkolloquium, um die wissenschaftliche Arbeit der Doktoranden kritisch zu begleiten und sie so in ihrer Entwicklung zu unterstützen. Dabei lassen sich im Programm der Freiberger Veranstaltung im Dezember 2010 zentrale Themen erkennen. Zum einen finden sich Facetten über Anwendungspotenziale der Business Intelligence als auch zum anderen Beiträge zur Definition und Einsatz von Services in Unternehmen. Ergänzend wird dies um Potenziale in der Softwarevisualisierung als auch durch einen Beitrag zur Erfolgsmessung von IT-Systemen. Wir freuen uns, Ihnen mit diesem Freiberger Arbeitspapier die Beiträge zur Verfügung stellen zu können, die traditionell in einem intensiven Austausch auf der Veranstaltung diskutiert werden, um so auch weitere Forschungsarbeiten anzuregen. -- The international recognition of research results in the scientific field of business information systems has increased in the recent years. Therefore the critical discourse on research topics has a growing emphasis. It is important to offer young scientists a platform for discussion and learning in a scientific debate about the respective scientific objective in the design and implementation of their own research and applied research methods. To promote dialogue between business information systems researchers of different focal points, the Middle German business information systems chairs from the Universities of Chemnitz, Dresden, Freiberg, Halle, Jena, and Leipzig organize a doctoral colloquium each semester to accompany the scientific work of young researches in a critical way in order to assist them in their development. The agenda shows the main topics of the event at the University of Freiberg in December 2010. Aspects related to potential applications of Business Intelligence as well as other contributions about the definition and usage of services in companies. This is in addition to the potentials of software visualization in the same way as analyzing success factors of IT systems. We are pleased to provide you the Freiberger working paper including the contributions of the participants that are traditionally discussed in an intense exchange at the meeting in order to stimulate further research.Business Intelligence,Entscheidungsunterstützung,Informationssysteme,Erfolgsfaktoren bei Informationssystemen,Softwarevisualisierung,SOA,Services,Business Intelligence,Decision Support,Information System,IS Success Factors,Software Visualization,SOA

Detection and analysis of near-miss clone genealogies

It is believed that identical or similar code fragments in source code, also known as code clones, have an impact on software maintenance. A clone genealogy shows how a group of clone fragments evolve with the evolution of the associated software system, and thus may provide important insights on the maintenance implications of those clone fragments. Considering the importance of studying the evolution of code clones, many studies have been conducted on this topic. However, after a decade of active research, there has been a marked lack of progress in understanding the evolution of near-miss software clones, especially where statements have been added, deleted, or modified in the copied fragments. Given that there are a significant amount of near-miss clones in the software systems, we believe that without studying the evolution of near-miss clones, one cannot have a complete picture of the clone evolution. In this thesis, we have advanced the state-of-the-art in the evolution of clone research in the context of both exact and near-miss software clones. First, we performed a large-scale empirical study to extend the existing knowledge about the evolution of exact and renamed clones where identifiers have been modified in the copied fragments. Second, we have developed a framework, gCad that can automatically extract both exact and near-miss clone genealogies across multiple versions of a program and identify their change patterns reasonably fast while maintaining high precision and recall. Third, in order to gain a broader perspective of clone evolution, we extended gCad to calculate various evolutionary metrics, and performed an in-depth empirical study on the evolution of both exact and near-miss clones in six open source software systems of two different programming languages with respect to five research questions. We discovered several interesting evolutionary phenomena of near-miss clones which either contradict with previous findings or are new. Finally, we further improved gCad, and investigated a wide range of attributes and metrics derived from both the clones themselves and their evolution histories to identify certain attributes, which developers often use to remove clones in the real world. We believe that our new insights in the evolution of near-miss clones, and about how developers approach and remove duplication, will play an important role in understanding the maintenance implications of clones and will help design better clone management systems

Verification, slicing, and visualization of programs with contracts

Tese de doutoramento em Informática (área de especialização em Ciências da Computação)As a specification carries out relevant information concerning the behaviour of a program, why not explore this fact to slice a program in a semantic sense aiming at optimizing it or easing its verification? It was this idea that Comuzzi, in 1996, introduced with the notion of postcondition-based slicing | slice a program using the information contained in the postcondition (the condition Q that is guaranteed to hold at the exit of a program). After him, several advances were made and different extensions were proposed, bridging the two areas of Program Verification and Program Slicing: specifically precondition-based slicing and specification-based slicing. The work reported in this Ph.D. dissertation explores further relations between these two areas aiming at discovering mutual benefits. A deep study of specification-based slicing has shown that the original algorithm is not efficient and does not produce minimal slices. In this dissertation, traditional specification-based slicing algorithms are revisited and improved (their formalization is proposed under the name of assertion-based slicing), in a new framework that is appropriate for reasoning about imperative programs annotated with contracts and loop invariants. In the same theoretical framework, the semantic slicing algorithms are extended to work at the program level through a new concept called contract based slicing. Contract-based slicing, constituting another contribution of this work, allows for the study of a program at an interprocedural level, enabling optimizations in the context of code reuse. Motivated by the lack of tools to prove that the proposed algorithms work in practice, a tool (GamaSlicer) was also developed. It implements all the existing semantic slicing algorithms, in addition to the ones introduced in this dissertation. This third contribution is based on generic graph visualization and animation algorithms that were adapted to work with verification and slice graphs, two specific cases of labelled control low graphs.Tendo em conta que uma especificação contém informação relevante no que diz respeito ao comportamento de um programa, faz sentido explorar este facto para o cortar em fatias (slice) com o objectivo de o optimizar ou de facilitar a sua verificação. Foi precisamente esta ideia que Comuzzi introduziu, em 1996, apresentando o conceito de postcondition-based slicing que consiste em cortar um programa usando a informação contida na pos-condicão (a condição Q que se assegura ser verdadeira no final da execução do programa). Depois da introdução deste conceito, vários avanços foram feitos e diferentes extensões foram propostas, aproximando desta forma duas áreas que até então pareciam desligadas: Program Verification e Program Slicing. Entre estes conceitos interessa-nos destacar as noções de precondition-based slicing e specification-based slicing, que serão revisitadas neste trabalho. Um estudo aprofundado do conceito de specification-based slicing relevou que o algoritmo original não é eficiente e não produz slices mínimos. O trabalho reportado nesta dissertação de doutoramento explora a ideia de tornar mais próximas essas duas áreas visando obter benefícios mútuos. Assim, estabelecendo uma nova base teórica matemática, os algoritmos originais de specification-based slicing são revistos e aperfeiçoados | a sua formalizacão é proposta com o nome de assertion-based slicing. Ainda sobre a mesma base teórica, os algoritmos de slicing são extendidos, de forma a funcionarem ao nível do programa; alem disso introduz-se um novo conceito: contract-based slicing. Este conceito, contract-based slicing, sendo mais um dos contributos do trabalho aqui descrito, possibilita o estudo de um programa ao nível externo de um procedimento, permitindo, por um lado, otimizações no contexto do seu uso, e por outro, a sua reutilização segura. Devido à falta de ferramentas que provem que os algoritmos propostos de facto funcionam na prática, foi desenvolvida uma, com o nome GamaSlicer, que implementa todos os algoritmos existentes de slicing semântico e os novos propostos. Uma terceira contribuição é baseada nos algoritmos genéricos de visualização e animação de grafos que foram adaptados para funcionar com os grafos de controlo de fluxo etiquetados e os grafos de verificação e slicing.Fundação para a Ciência e a Tecnologia (FCT) através da Bolsa de Doutoramento SFRH/BD/33231/2007Projecto RESCUE (contrato FCT sob a referência PTDC / EIA / 65862 /2006)Projecto CROSS (contrato FCT sob a referência PTDC / EIACCO / 108995 / 2008