M. Di Penta

Testing services and service-centric systems: challenges and opportunities

This paper provides users and system integrators with an overview of service-oriented architecture (SOA) testings fundamental technical issues and solutions, focusing on Web services as a practical implementation of the SOA model. The paper discusses SOA testing across two dimensions: testing perspectives, wherein various stakeholders have different needs and raise different testing requirements; and testing level, wherein each SOA testing level poses unique challenges

How Clones are Maintained: An Empirical Study

Despite the conventional wisdom concerning the risks related to the use of source code cloning as a software development strategy, several studies appeared in literature indicated that this is not true. In most cases clones are properly maintained and, when this does not happen, is because cloned code evolves independently. Stemming from previous works, this paper combines clone detection and co-change analysis to investigate how clones are maintained when an evolution activity or a bug fixing impact a source code fragment belonging to a clone class. The two case studies reported confirm that, either for bug fixing or for evolution purposes, most of the cloned code is consistently maintained during the same co-change or during temporally close co-changes

New Frontiers of Reverse Engineering

Comprehending and modifying software is at the heart of many software engineering tasks, and this explains the growing interest that software reverse engineering has gained in the last 20 years. Broadly speaking, reverse engineering is the process of analyzing a subject system to create representations of the system at a higher level of abstraction. This paper briefly presents an overview of the field of reverse engineering, reviews main achievements and areas of application, and highlights key open research issues for the future.

Analyzing cloning evolution in the Linux kernel

Abstract Identifying code duplication in large multi-platform software systems is a challenging problem. This is due to a variety of reasons including the presence of high-level programming languages and structures interleaved with hardware-dependent low-level resources and assembler code, the use of GUI-based configuration scripts generating commands to compile the system, and the extremely high number of possible different configurations. This paper studies the extent and the evolution of code duplications in the Linux kernel. Linux is a large, multi-platform software system; it is based on the Open Source concept, and so there are no obstacles in discussing its implementation. In addition, it is decidedly too large to be examined manually: the current Linux kernel release (2.4.18) is about three million LOCs. Nineteen releases, from 2.4.0 to 2.4.18, were processed and analyzed, identifying code duplication among Linux subsystems by means of a metric-based approach. The obtained results support the hypothesis that the Linux system does not contain a relevant fraction of code duplication. Furthermore, code duplication tends to remain stable across releases, thus suggesting a fairly stable structure, evolving smoothly without any evidence of degradation.

An approach to identify duplicated web pages

A relevant consequence of the expansion of the web and e-commerce is the growth of the demand of new web sites and web applications. As a result, web sites and applications are usually developed without a formalized process, and web pages are directly coded in an incremental way, where new pages are obtained by duplicating existing ones. Duplicated web pages, having the same structure and just differing for the data they include, can be considered as clones. The identification of clones may reduce the effort devoted to test, maintain and evolve web sites and applications. Moreover, clone detection among different web sites aims to detect cases of possible plagiarism. In this paper we propose an approach. based on similarity metrics, to detect duplicated pages in web sites and applications, implemented with HTML language and ASP technology. The proposed approach has been assessed by analyzing several web sites and Web applications. The obtained results are reported in the paper with respect to some case studies.

Assessing and improving state-based class testing: a series of experiments

This work describes an empirical investigation of the cost effectiveness of well-known state-based testing techniques for classes or clusters of classes that exhibit a state-dependent behavior. This is practically relevant as many object-oriented methodologies recommend modeling such components with statecharts which can then be used as a basis for testing. Our results, based on a series of three experiments, show that in most cases state-based techniques are not likely to be sufficient by themselves to catch most of the faults present in the code. Though useful, they need to be complemented with black-box, functional testing. We focus here on a particular technique, Category Partition, as this is the most commonly used and referenced black-box, functional testing technique. Two different oracle strategies have been applied for checking the success of test cases. One is a very precise oracle checking the concrete state of objects whereas the other one is based on the notion of state invariant (abstract states). Results show that there is a significant difference between them, both in terms of fault detection and cost. This is therefore an important choice to make that should be driven by the characteristics of the component to be tested, such as its criticality, complexity, and test budget.

An experimental investigation of formality in UML-based development

The object constraint language (OCL) was introduced as part of the Unified Modeling Language (UML). Its main purpose is to make UML models more precise and unambiguous by providing a constraint language describing constraints that the UML diagrams alone do not convey, including class invariants, operation contracts, and statechart guard conditions. There is an ongoing debate regarding the usefulness of using OCL in UML-based development, questioning whether the additional effort and formality is worth the benefit. It is argued that natural language may be sufficient, and using OCL may not bring any tangible benefits. This debate is in fact similar to the discussion about the effectiveness of formal methods in software engineering, but in a much more specific context. This paper presents the results of two controlled experiments that investigate the impact of using OCL on three software engineering activities using UML analysis models: detection of model defects through inspections, comprehension of the system logic and functionality, and impact analysis of changes. The results show that, once past an initial learning curve, significant benefits can be obtained by using OCL in combination with UML analysis diagrams to form a precise UML analysis model. But, this result is however conditioned on providing substantial, thorough training to the experiment participants.

Search-based techniques applied to optimization of project planning for a massive maintenance project

This paper evaluates the use of three different search-based techniques, namely genetic algorithms, hill climbing and simulated annealing, and two problem representations, for planning resource allocation in large massive maintenance projects. In particular, the search-based approach aims to find an optimal or near optimal order in which to allocate work packages to programming teams, in order to minimize the project duration. The approach is validated by an empirical study of a large, commercial Y2K massive maintenance project, which compares these techniques with each other and with a random search (to provide base line comparison data). Results show that an ordering-based genome encoding (with tailored cross over operator) and the genetic algorithm appear to provide the most robust solution, though the hill climbing approach also performs well. The best search technique results reduce the project duration by as much as 50%.

An approach to classify software maintenance requests

When a software system critical for an organization exhibits a problem during its operation, it is relevant to fix it in a short period of time, to avoid serious economical losses. The problem is therefore noticed by the organization in charge of the maintenance, and it should be correctly and quickly dispatched to the right maintenance team. We propose to automatically classify incoming maintenance requests (also said tickets), routing them to specialized maintenance teams. The final goal is to develop a router working around the clock, that, without human intervention, dispatches incoming tickets with the lowest misclassification error, measured with respect to a given routing policy. 6000 maintenance tickets from a large, multi-site, software system, spanning about two years of system in-field operation, were used to compare and assess the accuracy of different classification approaches (i.e., Vector Space model, Bayesian model, support vectors, classification trees and k-nearest neighbor classification). The application and the tickets were divided into eight areas and pre-classified by human experts. Preliminary results were encouraging, up to 84% of the incoming tickets were correctly classified.

Object-oriented design patterns recovery

Abstract Object-Oriented (OO) design patterns are an emergent technology: they are reusable micro-architectures, high-level building blocks. A system which has been designed using well-known, documented and accepted design patterns is also likely to exhibit good properties such as modularity, separation of concerns and maintainability. While for forward engineering the benefits of using design patterns are clear, using reverse engineering technologies to discover instances of patterns in a software artifact (e.g., design or code) may help in several key areas, among which are program understanding, design-to-code traceability and quality assessment. This paper describes a conservative approach and experimental results, based on a multi-stage reduction strategy using OO software metrics and structural properties to extract structural design patterns from OO design or C++ code. To assess the effectiveness of the pattern recovery approach, a process and a portable tool suite written in Java, remotely accessible by means of any WEB browser, has been developed. The developed system and experimental results on 8 industrial software (design and code) and 200,000 lines of public domain C++ code are presented.