Modèles de mesure de la qualité des logiciels

National audienceDe manière générale, un logiciel de qualité s'entend comme un logiciel capable de répondre parfaitement aux attentes du client, le tout sans défaut d'exécution. Ainsi, on détermine la qualité logicielle comme un ensemble de règles et de principes à suivre au cours du développement d'une application afin de concevoir un logiciel répondant à ces attentes1 [ABDT04]. La NASA par exemple, a déterminé un ensemble de procédures, d'instructions de travail et de règles pour s'assurer que chaque étape du développement s'effectue de manière adéquate2 [EBM06]. La qualité d'un logiciel se reflète non seule- ment dans les processus de développement mais aussi dans la qualité des éléments qui le constituent, la documentation, la présence de tests..... Mesurer la qualité d'un logiciel consiste alors à déterminer son adéquation par rapport aux objectifs de départ et aux standards de programmation. Il faut donc définir précisément ce que l'application doit faire et comment elle doit le faire, tant d'un point de vue fonctionnel que d'un point de vue technique. Une fois ces objectifs fixés, on peut alors appliquer un ensemble de règles et de mesures afin de calculer la différence entre objectifs attendus et réalisation obtenue. Obtenir une mesure de la qualité permet à la fois d'avoir une image précise du logiciel mesuré mais aussi de déterminer le comportement de celui-ci dans le temps : quels sont les risques de bogues, les éventuelles failles sécuritaires, les difficultés de maintenance, les freins à l'évolution, la viabilité à long terme, etc. Un des objectifs de la mesure de la qualité logicielle consiste à sensibiliser les équipes de développement sur leur méthodes de programmation. En effet, mesurer la qualité a également pour objectif de fournir des bonnes pratiques de travail et des indicateurs permettant d'augmenter la qualité des futurs développements. Pour obtenir une image complète de la qualité d'un logiciel on fait appel à un modèle de qualité. Celui-ci regroupe des règles qui décrivent ce que doit être un logiciel de qualité et le répertorie en différents groupes. Le modèle est ensuite évalué à partir de mesures obtenues grâce au code source, à la documentation, aux annexes techniques, aux règles de conception ou tout autre information disponible pour le projet. Un modèle de qualité comporte souvent plusieurs niveaux de lecture. Il se compose d'une couche de haut niveau qui décrit la qualité selon un point de vue très généraliste. Ce premier niveau est ensuite décrit plus spécifiquement, le tout pour atteindre ensuite le plus bas niveau, détaillé et technique. Dans ce chapitre nous présentons quelques modèles de qualité standards pour en- suite détailler le modèle Squale. Il s'agit d'un modèle de qualité open source développé depuis plusieurs années dans un contexte industriel avec Air France-KLM et PSA Peugeot- Citroen3. Ce modèle de qualité offre à la fois une vue générale de la qualité du projet mesuré mais également une vue détaillée orientée développeur. Il propose une manière d'agréger les données issues du projet de façon à ne perdre aucune information. Il per- met également de passer d'une vue détaillée à une vue globale et vice et versa. Squale est un modèle qui détermine la qualité d'une application mais il propose également un plan de remédiation conçu comme une aide à la décision

Visualization of Practices and Metrics (Workpackage 1.2)

Measuring applications is a challenge and one of the goal of the Squale project is to propose a sound quality model. Now presenting the results of such analysis is also a challenge since it is complex to output and present to the user for the following rea- sons: first a lot of data should be presented and at different audience. Second displaying information is one aspect another one is navigating the information. Finally it is im- portant not to overwhelm the users with too much visualizations. This workpackage presents a state of the art in terms of software visualization approaches that are specif- ically designed to display metrics. In addition it sets up the context for the application of such visualization to practices

SQUALE -- Software QUALity Enhancement

PresentationInternational audienceThe Squale project was born from industrial effort to control software quality. Its goals are to refine and enhance Qualixo Model, a software-metric based quality model already used by large companies in France (Air France-KLM, PSA Peugeot-Citroën) and to support the estimation of return on investment produced by software quality. Qualixo Model is a software quality model based on the aggregation of software metrics into higher level indicators called practices, criterias and factors. The coordination of Squale is carried out by Qualixo

Practices in the Squale Quality Model (Squale Deliverable 1.3)

This document presents the Squale Software Quality Model as defined by Qualixo. It first reviews existing quality models and presents the Squale model with its particular- ity, namely a practice layer. Then it reviews in details an instance of this Squale Model with its Factors, Criteria and Practices, giving precise definitions and description1. Fi- nally, it discusses possible future enhancements of this model like new practices or its agreement with the program life-cycle and the change of needs during this life cycle

The Squale Model - A Practice-based Industrial Quality Model

International audienceISO 9126 promotes a three-level model of quality (fac- tors, criteria, and metrics) which allows one to assess qual- ity at the top level of factors and criteria. However, it is dif- ficult to use this model as a tool to increase software quality. In the Squale model, we add practices as an intermediate level between metrics and criteria. Practices abstract away from raw information (metrics, tool reports, audits) and provide technical guidelines to respect. Moreover, practice marks are adjusted using formulae to suit company development habits or exigences: for example bad marks are stressed to point to places which need more attention. The Squale model has been developed and validated over the last couple of years in an industrial setting with Air France-KLM and PSA Peugeot-Citroën

Software metric for Java and C++ practices (Workpackage 1.1)

The objective of this deliverable is to define a catalog of software met- rics. In particular we analyze the metrics used in the Squale Model and tool. In addition it offers a coherent set of software metrics for object-oriented languages on top of which Squale practices will be based. There is a plethora of software metrics and a large amount of research articles. Still there is a lack for a serious and practically-oriented evaluation of metrics. Often metrics lacks the property that the software reengineer or quality expert can easily understand the situation summa- rized by the metrics. In particular since the exact notion of coupling and cohesion is complex, a particular focus on such point is important

The Squale Model - A Practice-based Industrial Quality Model

ISO 9126 promotes a three-level model of quality (fac- tors, criteria, and metrics) which allows one to assess qual- ity at the top level of factors and criteria. However, it is dif- ficult to use this model as a tool to increase software quality. In the Squale model, we propose the adjunction of prac- tices as an intermediate level between metrics and crite- ria. Practices abstract from raw information at the source (metrics, tool reports, audits) to provide the developer with technical guidelines to respect. Moreover, practice marks can be adjusted using formulae to suit company develop- ment habits or exigences: for example bad marks can be stressed to point to places which need the most attention. Dashboards allow one to spot faulty practices and find the source elements responsible for the bad marks. The Squale model has been developed and validated over the last cou- ple of years in an industrial setting with Air France-KML and PSA Peugeot-Citroën. Over 100 projects with a total of more than seven millions lines of code have been assessed and steered using Squale

The Squale Model - A Practice-based Industrial Quality Model

International audienceISO 9126 promotes a three-level model of quality (fac- tors, criteria, and metrics) which allows one to assess qual- ity at the top level of factors and criteria. However, it is dif- ficult to use this model as a tool to increase software quality. In the Squale model, we add practices as an intermediate level between metrics and criteria. Practices abstract away from raw information (metrics, tool reports, audits) and provide technical guidelines to respect. Moreover, practice marks are adjusted using formulae to suit company development habits or exigences: for example bad marks are stressed to point to places which need more attention. The Squale model has been developed and validated over the last couple of years in an industrial setting with Air France-KLM and PSA Peugeot-Citroën

An empirical model for continuous and weighted metric aggregation

International audienceIt is now understood that software metrics alone are not enough to characterize software quality. To cope with this problem, most of advanced and/or industrially validated quality models aggregate software metrics: for example, cy- clomatic complexity is combined with test coverage to stress the fact that it is more important to cover complex methods than accessors. Yet, aggregating and weighting metrics to produce quality indexes is a difficult task. Indeed certain weighting approaches may lead to abnormal situations where a developer increasing the quality of a software component sees the overall quality degrade. Finally, mapping combinations of metric values to quality indexes may be a problem when using thresholds. In this paper, we present the problems we faced when designing the Squale quality model, then we present an empirical solution based on weighted aggregations and on continuous functions. The solution has been termed the Squale quality model and validated over 4 years with two large multinational companies: Air France-KLM and PSA Peugeot- Citroen

A Flavor Lactone Mimicking AHL Quorum-Sensing Signals Exploits the Broad Affinity of the QsdR Regulator to Stimulate Transcription of the Rhodococcal qsd Operon Involved in Quorum-Quenching and Biocontrol Activities

In many Gram-negative bacteria, virulence, and social behavior are controlled by quorum-sensing (QS) systems based on the synthesis and perception of N-acyl homoserine lactones (AHLs). Quorum-quenching (QQ) is currently used to disrupt bacterial communication, as a biocontrol strategy for plant crop protection. In this context, the Gram-positive bacterium Rhodococcus erythropolis uses a catabolic pathway to control the virulence of soft-rot pathogens by degrading their AHL signals. This QS signal degradation pathway requires the expression of the qsd operon, encoding the key enzyme QsdA, an intracellular lactonase that can hydrolyze a wide range of substrates. QsdR, a TetR-like family regulator, represses the expression of the qsd operon. During AHL degradation, this repression is released by the binding of the γ-butyrolactone ring of the pathogen signaling molecules to QsdR. We show here that a lactone designed to mimic quorum signals, γ-caprolactone, can act as an effector ligand of QsdR, triggering the synthesis of qsd operon-encoded enzymes. Interaction between γ-caprolactone and QsdR was demonstrated indirectly, by quantitative RT-PCR, molecular docking and transcriptional fusion approaches, and directly, in an electrophoretic mobility shift assay. This broad-affinity regulatory system demonstrates that preventive or curative quenching therapies could be triggered artificially and/or managed in a sustainable way by the addition of γ-caprolactone, a compound better known as cheap food additive. The biostimulation of QQ activity could therefore be used to counteract the lack of consistency observed in some large-scale biocontrol assays