Michel R. V. Chaudron

Component-Based Development Process and Component Lifecycle

The process of component- and component-based system development differs in many significant ways from the classical development process of software systems. The main difference is in the separation of the development process of components from the development process of systems. This fact has a significant impact on the development process. Since the component-based approach is a relatively young approach in software engineering, the main emphasis in the area has been in development of technologies, while process modeling is still an unexplored area. This paper analyses the basic characteristics of the component-based approach and its impact on the development process and lifecycle models. The generic lifecycle of component-based systems and the lifecycle of components are discussed, and the different types of development processes are discussed in detail: architecture-driven component development, productline development and COTS-based development. Finally a short case study illustrates the principles and specifics of component-based processes.

Managing Model Quality in UML-Based Software Development

With the advent of UML and MDA, models play an increasingly important role in software development. Hence, the management of the quality of models is of key importance for completing projects succesfully. However, existing approaches towards software quality focus on the implementation and execution of systems. These existing quality models cannot be straightforwardly mapped to the domain of UML models as source code and models differ in several essential ways (level of abstraction, precision, completeness and consistency). In this paper we present a quality model for managing UML-based software development. This model enables identifying the need for actions for quality improvement already in early stages of the life-cycle. Early actions for quality improvement are less resource intensive and, hence, less cost intensive than later actions. We discuss our experiences in applying the quality model to several industrial case studies. Finally we present a tool that visualizes our quality model. This tool helps in relating management level quality data to detailed data about specific quality subcharacteristics

Effects of defects in UML models: an experimental investigation

The Unified Modeling Language (UML) is the de facto standard for designing and architecting software systems. UML offers a large number of diagram types that can be used with varying degree of rigour. As a result UML models may contain consistency defects. Previous research has shown that industrial UML models that are used as basis for implementation and maintenance contain large numbers of defects. This study investigates to what extent implementers detect defects and to what extent defects cause different interpretations by different readers. We performed two controlled experiments with a large group of students (111) and a group of industrial practitioners (48). The experiments results show that defects often remain undetected and cause misinterpretations. We present a classification of defect types based on a ranking of detection rate and risk for misinterpretation. Additionally we observed effects of using domain knowledge to compensate defects. The results are generalizable to industrial UML users and can be used for improving quality assurance techniques for UML-based development.

Modelling of input-parameter dependency for performance predictions of component-based embedded systems

The guaranty of meeting the timing constraints during the design phase of real-time component-based embedded software has not been realized. To satisfy real-time requirements, we need to understand behaviour and resource usage of a system over time. In this paper, we address both aspects in detail by observing the influence of input data on the system behaviour and performance. We extend an existing scenario simulation approach that features the modelling of input parameter dependencies and simulating the execution of the models. The approach enables specification of the dependencies in the component models, as well as initialisation of the parameters in the application scenario model. This gives a component-based application designer an explorative possibility of going through all possible execution scenarios with different parameter initialisations, and finding the worst-case scenarios where the predicted performance does not satisfy the requirements. The identification of these scenarios is important because it avoids system redesign at the later stage. In addition, the conditional behaviour and resource usage modelling with respect to the input data provide more accurate prediction.

Generalizing Consistency Checking between Software Views

Inconsistencies between software views are a source of errors for software systems. In this paper we present a general approach that aids in finding inconsistencies between different views. This approach supports both intra phase consistency checking and inter phase consistency checking. The approach is suitable for detecting consistency problems between, for example, multiple diagrams in a UML design as well as between a design and an implementation. The approach is based on verification of rules using relation partition algebra. In this paper, we present two types of rules: obligations and the more commonly used constraints, which can be viewed as lower bounds and upper bounds, respectively. To check consistency between views, rules are derived from one view, the so-called prevailing view, and imposed on another view, the so-called subordinate view. Because our approach does not prescribe which views are prevailing, it can be used in any arbitrary process. Violations to rules can be expressed in terms of either the prevailing view or the subordinate view. Exceptions to rules are easiliy embedded in our general approach to consistency checking.

COTS Selection Best Practices in Literature and in Industry

This paper presents an extensive literature survey of the software COTS component selection methods published to date, followed by a meta-model consolidating the activities and practices of these methods. Together with data collected from practitioners and researchers in the embedded systems domain, we provide concrete recommendations which will enable organizations to identify suitable practices when designing a customized selection processes.

Interactive Views to Improve the Comprehension of UML Models - An Experimental Validation

Software development is becoming more and more model-centric. As a result models are used for a large variety of purposes, such as quality analysis, understanding, and maintenance. We argue that the UML and related existing tooling does not offer sufficient support to the developer to understand the models and evaluate their quality. We have proposed and implemented a collection of views to increase model understanding: MetaView, ContextView, MetricView, and UML-City-View. The purpose of this experiment is to validate whether there is a difference between the proposed views and the existing views with respect to comprehension correctness and comprehension effort. The comprehension task performed by the subjects was to answer a questionnaire about a model. 100 MSc students with relevant background knowledge have participated in the experiment. The results are statistically significant and show that the correctness is improved by 4.5% and that the time needed is reduced by 20%.

CARAT: a toolkit for design and performance analysis of component-based embedded systems

Solid frameworks and toolkits for design and analysis of embedded systems are of high importance, since they enable early reasoning about critical properties of a system. This paper presents a software toolkit that supports the design and performance analysis of real-time component-based software architectures deployed on heterogeneous multiprocessor platforms. The tooling environment contains a set of integrated tools for (a) component storage and retrieval, (b) graphics-based design of software and hardware architectures, (c) performance analysis of the designed architectures and, (d) automated code generation. The cornerstone of the toolkit is a performance analysis framework that automates composition of the individual component models into a system executable model, allows simulation of the system model and gives design-time predictions of key performance properties like response time, data throughput, and usage of hardware resources. The efficiency of this toolkit was illustrated on a car radio navigation benchmark system

Integrity management in component based systems

There is a need for mechanisms for maintaining and restoring software integrity on deployed systems. Dynamic replacement, removal and addition of components in deployed systems is supported by most component models. This is needed to enable the software on a device to evolve in the period that it is owned by a consumer, but endangers the integrity of the software on these devices. For high volume consumer devices the challenge is to keep the devices operating reliable and robust in the period that it is owned, used and possibly reconfigured by a consumer. To this end, we propose mechanisms and tools, for maintaining system integrity on deployed systems.

Evaluation of static properties for component-based architectures

Early assessment of the compositional properties of component compositions is one of the hottest issues in component-based architecting. We describe a method for evaluating the static properties of an architecture, given the features of its constituents. The estimation framework is based on composition rules and the specification of the static properties of the components by means of a reflection interface. Two evaluation approaches, exhaustive and selective, provide a flexible trade-off between the estimation effort and the necessary precision. The method was successfully applied to the Koala component model for estimating the static memory consumption.