The paper presents a controlled experiment, focusing on the impact of applying quality design principles such as the ones provided by P. Coad and E. Yourdon (1991) on the maintainability of object oriented designs. Results, which repeat the findings of a previous study, strongly suggest that such design principles have a beneficial effect on the maintainability of object oriented designs. It is argued that object oriented designs are sensitive to poor design practices because the cognitive complexity introduced becomes increasingly unmanageable. However, as our ability to generalize these results is limited, they should be considered as preliminary, i.e., it is very likely that they can only be generalized to programmers with little object oriented training and programming experience. Such programmers can, however, be commonly found on maintenance projects. As well as additional research, external replications of this study are required to confirm the results and achieve confidence in these findings.

The increasing importance being placed on software measurement has led to an increased amount of research developing new software measures. Given the importance of object-oriented development techniques, one specific area where this has occurred is coupling measurement in object-oriented systems. However, despite a very interesting and rich body of work, there is little understanding of the motivation and empirical hypotheses behind many of these new measures. It is often difficult to determine how such measures relate to one another and for which application they can be used. As a consequence, it is very difficult for practitioners and researchers to obtain a clear picture of the state of the art in order to select or define measures for object-oriented systems. This situation is addressed and clarified through several different activities. First, a standardized terminology and formalism for expressing measures is provided which ensures that all measures using it are expressed in a fully consistent and operational manner. Second, to provide a structured synthesis, a review of the existing frameworks and measures for coupling measurement in object-oriented systems takes place. Third, a unified framework, based on the issues discovered in the review, is provided and all existing measures are then classified according to this framework. This paper contributes to an increased understanding of the state-of-the-art.

The paper aims at empirically exploring the relationships between existing object oriented coupling, cohesion, and inheritance measures and the probability of fault detection in system classes during testing. The underlying goal of such a study is to better understand the relationship between existing product measurement in OO systems and the quality of the software developed. It is shown that by using a subset of existing measures, accurate models can be built to predict in which classes most of the faults are likely to lie in. By inspecting 48% of the classes, it is possible to find 95% of the faults. Besides the size of classes, the frequency of method invocations and the depth of inheritance hierarchies seem to be the main driving factors of fault proneness.

No abstract available.

Presents a controlled experiment focusing on the following issues. (1) Are object-oriented design documents easier to understand and modify than structured design documents? (2) Must they comply with quality design principles, such as the ones provided by Coad and Yourdon (1991)? (3) What is the impact of such design principles on the understandability and modifiability of design documents? The results of the experiment strongly suggest that such design principles have a beneficial effect on the maintainability of object-oriented design documents. However, there is no strong evidence regarding the alleged higher maintainability of object-oriented design documents over structured design documents. Furthermore, the results suggest that object-oriented design documents are more sensitive to poor design practices, in part because their cognitive complexity becomes increasingly unmanageable. However, as our ability to generalise these results is limited, they should be considered as preliminary, i.e. it is very likely that they can only be generalised to programmers with little object-oriented training. However, such programmers can be commonly found on maintenance projects

The object-oriented paradigm is becoming increasingly popular as a result of expert opinion and anecdotal evidence and not on the basis of sound empirical data. The questionnaire survey was undertaken as part of a programme of research to validate unsupported claims about the paradigm. The questionnaire follows structured interviews of experienced object-oriented developers with the intention of confirming the findings on a wider practitioner group. It was posted to relevant electronic newsgroups and to members of an object-oriented (postal) mailing list. The survey received 167 responses to the electronic questionnaire and 119 responses (30% response rate) to the postal version. Results show that respondents are of the view that: (i) the object-oriented paradigm has advantages over other paradigms in terms of ease of analysis and design, programmer productivity, software reuse, and ease of maintenance; (ii) inheritance can introduce difficulties when trying to understand object-oriented software; (iii) missing design documentation and poor or inappropriate design are prevalent problems; (iv) maintenance causes degradation of object-oriented software, but less frequently than conventional software; (v) C++ has many deficiencies in comparison to other purer object-oriented languages.

The empirical study was undertaken as part of a programme of research to explore unsupported claims about the object-oriented paradigm: a series of experiments tested the effect of inheritance on the maintainability of object-oriented software. Subjects were asked to modify object-oriented software with a hierarchy of 3 levels of inheritance depth and equivalent object-based software with no inheritance. The collected timing data showed that subjects maintaining object-oriented software using inheritance performed the modification tasks, on average, approximately 20% quicker than those maintaining equivalent object-based software with no inheritance. An initial inductive analysis revealed that 2 out of 3 subjects performed faster when maintaining the object-oriented software with inheritance. The findings are sufficiently important that attempts to verify the results should be made by independent researchers. Subsequent studies should seek to scale up the findings to the maintenance of more complex software by professional programmers.

Empirical studies carried out to help understand the problems of software maintenance are widely held to be of value. A view perhaps less widely recognised within the software engineering domain is that experiments should be replicated both internally and externally to validate the results and build up a cohesive body of knowledge. This paper presents the external replication findings of an experiment which tested the benefits to maintenance of using modular code against nonmodular (monolithic) code. The results of our replication were strikingly different from those of the original which showed that a modular program could be maintained significantly faster than an equivalent monolithic version. An inductive analysis, undertaken to investigate the reasons for this, uncovered evidence of an ability effect and the suggestion that the experiment may have been too artificial.>