Design by Contract: The Lessons of Ariane
Design by contract is the principle that the interfaces between modules of a software system-especially a mission-critical one-should be governed by precise specifications. The contracts cover mutual obligations (pre-conditions), benefits (post-conditions), and consistency constraints (invariants). Together, these properties are known as assertions, and are directly supported in some design and programming languages. A recent $500 million software error provides a sobering reminder that this principle is not just a pleasant academic ideal. On June 4, 1996, the maiden flight of the European Ariane 5 launcher crashed, about 40 seconds after takeoff. The rocket was uninsured. The French space agency, CNES (Centre National d'Etudes Spatiales), and the European Space Agency (ESA) immediately appointed an international inquiry board. The board makes several recommendations with respect to software process improvement. There is a simple lesson to be learned from this event: reuse without a precise, rigorous specification mechanism is a risk of potentially disastrous proportions. It is regrettable that this lesson has not been heeded by such recent designs as IDL, Ada 95 or Java. None of these languages has built-in support for design by contract. Effective reuse requires design by contract. Without a precise specification attached to each reusable component, no-one can trust a supposedly reusable component. Without a specification, it is probably safer to redo than to reuse.

title: Library Design

title: Concurrent object-oriented programming on .NET
abstract: The SCOOP model (Simple concurrent object-oriented programming) offers a comprehensive approach to building high-quality concurrent and distributed systems. The model takes advantage of the inherent concurrency implicit in object-oriented programming to provide programmers with a simple extension enabling them to produce concurrent applications with little more effort than sequential ones. In the paper, the authors discuss the basic concepts of the model, such as processors and separate objects. They also present SCOOPLI, a library implementation of SCOOP for the .NET platform. They show how SCOOP concepts are mapped to .NET constructs, and discuss distributed programming with SCOOPLI, with a focus on .NET Remoting capabilities. Several programming examples illustrate the discussion.

title: Providing Trusted Components to the Industry
abstract: The software industry stands on feet of clay. However carefully we may strive to build correct and reliable software, we have no way of guaranteeing the quality of the result. Building correct and reliable software depends on the quality of so much else, from the hardware and the operating system to the compiler and the runtime libraries. And any significant software system has so many details and components of its own that we can hardly expect to get everything right if we do it all by ourselves. We describe an ambitious but realistic project that combines the ideas of reuse and formality with other more pragmatic techniques. The goal is to provide the entire software industry with a powerful set of reusable components deserving a high degree of trust.

title: A Note on Computing Multiple Sums
abstract: In a recent paper, 1 ~:method was given for computing multidimensional sums in FORTRAN in a particular case •. We show that the general problem of computing mUltidimensional sums is best expressed by a recursive definition which can then be translated into a programming language. The method is applied to an example optimization"problem. ' "

title: Dependable Software
abstract: Achieving software reliability takes many complementary tech-niques, directed at the process or at the products. This survey summarizes some of the most fruitful ideas.

title: Prediction of Material Properties from Chemical Structures. The Clearing Temperature of Nematic Liquid Crystals Derived from Their Chemical Structures by Artificial Neural Networks
abstract: The prediction of properties of molecules just on the basis of their chemical structures is desirable to selectively make molecules that have the wanted properties, like biological activity, viscosity, or toxicity. Here, we present an example of a new way to predict a property from the chemical structure of a chemically heterogeneous class of compounds. The clearing temperatures of nematic liquid-crystalline phases of 17383 compounds were used to train neural networks to derive this material property directly from their chemical structure. The trained neural networks were subsequently tested with 4345 structural patterns of molecules unknown to the networks to assess their predictive value. The clearing temperatures were predicted by the best network with a standard deviation of 13 degrees.

title: Issues in practical application of an adaptive interface
abstract: The authors have been developing a prototype sys[em for installation in an operationat business environment. During the development, a number of issues have been encountered. These include: ● constraints arising from placing prototypes in operational environments . lack of guidelines for selecting types of adaptation ● difficulty determining adaptation criteria ● difficulty obtaining necessary data from users ● lack of guidelines for making information display decisions ● problems in testing ‘real world’ interfaces These issues are not readily solved with more sophisticated adaptation algorithms; rather. they point out the need for CO1Iect ing more information from attempts to bring intelligent interfaces to complex business environments.

title: Age group differences in world wide web navigation
abstract: In this study, we examined the effects of age and training on efficiency and preferences in a World Wide Web search activity. Older participants were able to complete most of the tasks, but took more steps to find the information than did younger adults. Factors in this inefficiency were patterns of returning to the home page and revisiting pages that had been seen before during a search. Interactive training improved efficiency and altered preferences. We discuss implications for training and design.

title: Design and evaluation of an adaptive icon toolbar
abstract: As information systems become increasingly important in many different domains, the potential to adapt them to individual users and their needs also becomes more important. Adaptive user interfaces offer many possible ways to adjust displays and improve procedures for a user's individual patterns of work. This paper describes an attempt to design an adaptive user interface in a computer environment familiar to many users. According to one classification of adaptive user interfaces, the adaptive bar described in this paper would be classified as a user-controlled self-adaptation system.At the user's convenience, the adaptive bar offers suggestions for adding or removing command icons, based on the frequency and probability of specific commands. It also implements these changes once the user has agreed to them. Beyond the adaptive bar, the general behavior of the whole user interface does not change, thereby allowing the user to maintain a clear general model of the system. This paper describes the decision-making algorithm implemented in the bar. It also describes the bar's self-adaptive behavior of displaying the frequency of each icon's use through the icon's size. Finally, we present some encouraging preliminary results of evaluations by users.