Software productivity has been steadily increasing over the last 30 years, but not enough to close the gap between the demands placed on the software industry and what the state of the practice can deliver [22,39]; nothing short of an order of magnitude increase in productivity will extricate the software industry from its perennial crisis [39,67]. Several decades of intensive research in software engineering and artificial intelligence left few alternatives but sofware reuse as the (only) realistic approach to bring about the gains of productivity and quality that the software industry needs. In this paper, we discuss the implications of reuse on the production, with an emphasis on the technical challenges. Software reuse involves building software that is reusable by design, and building with reusable software. Software reuse includes reusing both the products of previous software projects, and the processes deployed to produce them, leading to a wide spectrum of reuse approaches, from the building blocks (reusing products) approach on one hand, to the generative or reusable processor (reusing processes) on the other [68]. We discuss the implications of such appproaches on the organization, control, and method of software development and discuss proposed models for their economic analysis. Software reuse benefits from methodologies and tools to: 1) build more readily reusable software, and 2) locate, evaluate, and tailor reusable software, the latter being critical for the building blocks approach. Both sets of issues are discussed in this paper, with a focus on application generators and object-oriented development for the first, and a thorough discussion of retrieval techniques for software components, component composition (or bottom-up design) and transformational systems for the second. We conclude by highlighting areas that, in our opinion, are worthy of further investigation.

In this paper we present a method of code imple-mentation that works in conjunction with collab-oration and responsibility based analysis model-ing techniques to achieve better code reuse and resilience to change. Our approach maintains a closer mapping from responsibilities in the analy-sis model to entities in the implementation. In so doing, it leverages the features of flexible design and design reuse found in collaboration-based de-sign models to provide similar adaptability and reuse in the implementation. Our approach re-quires no special development tools and uses only standard features available in the C++ language. In an earlier paper we described the basic mech-anisms used by our approach and discussed its advantages in comparison to the framework ap-proach. In this paper we show how our approach combines code and design reuse, describing spe-cific techniques that can be used in the develop-ment of larger applications. 1

In several works on design methodologies, design patterns, programming language design and application frameworks, the need for adequate higher-level program entities that capture the patterns of collaboration between several classes has been recognized. The idea is that in general the unit of reuse is not a single class, but a slice of behavior affecting a set of collaborating classes. The absence of large-scale components for expressing these collaborations makes object-oriented programs more difficult to maintain and reuse, because functionality is spread over several methods and it becomes difficult to get the "big picture". In this paper, we propose Adaptive Plug and Play Components to serve this need. These components are designed such that they not only facilitate the construction of complex software by making the collaborations explicit, but they do so in a manner that supports the evolutionary nature of both structure and behavior. 1 Introduction The step from proc...

. A critical concern in the reuse of software is the propagation of changes made to reusable artifacts. Without techniques to manage these changes, multiple versions of these artifacts will propagate through different systems and reusers will not be able to benefit from improvements to the original artifact. We propose to codify the management of change in a software system by means of reuse contracts that record the protocol between managers and users of a reusable asset. Just as real world contracts can be extended, amended and customised, reuse contracts are subject to parallel changes encoded by formal reuse operators: extension, refinement and concretisation. Reuse contracts and their operators serve as structured documentation and facilitate the propagation of changes to reusable assets by indicating how much work is needed to update previously built applications, where and how to test and how to adjust these applications. 1 Introduction It has become a well-known fact that the...

We present and evaluate an automatic tool for extracting algebraic specifications from Java classes. Our tool maps a Java class to an algebraic signature and then uses the signature to generate a large number of terms. The tool evaluates these terms and based on the results of the evaluation, it proposes equations. Finally, the tool generalizes equations to axioms and eliminates many redundant axioms. Since our tool uses dynamic information, it is not guaranteed to be sound or complete. However, we manually inspected the axioms generated in our experiments and found them all to be correct.

An object-oriented application framework provides a generic design within a given domain and a reusable implementation of that design. Frameworks have great potential for reuse, but that potential can only be achieved if the framework can be understood and used effectively by application developers. The complexity of the design and implementation of a framework can make understanding the framework difficult, and so good documentation and guidance to the framework user is needed. Several methods exist for documenting the design of the framework, but less work has been done on documenting the purpose of the framework and how it is intended to be used. In this paper, we introduce the concept of hooks as a means of documenting and providing guidance on the intended use of a framework. Each hook provides a concise solution to a focused requirement or problem within the context of the framework. Solutions for more complex requirements can be provided by combining several hooks. A discussion ...

Testing is an important part of any software development project, and can typically surpass more than half of the development cost. For safety-critical computer based systems, testing is even more important due to stringent reliability and safety requirements. However, most safety-critical computer based systems are real-time systems, and the majority of current testing and debugging techniques have been developed for sequential (non real-time) programs. These techniques are not directly applicable to real-time systems, since they disregard issues of timing and concurrency. This means that existing techniques for reproducible testing and debugging cannot be used. Reproducibility is essential for regression testing and cyclic debugging, where the same test cases are run repeatedly with the intention of verifying modified program code or to track down errors. The current trend of consumer and industrial applications goes from single microcontrollers to sets of distributed micro-controllers, which are even more challenging than handling real-time per-see, since multiple loci of observation and control additionally must be considered. In this thesis we try to remedy these problems by presenting an integrated approach to monitoring, testing, and debugging of distributed real-time systems. For monitoring

Reflective programming languages are those where users' programs are allowed to customize in an organized way the behavior of the language to their own needs. For ten years now, most of the work on reflection revolved around the definition and the implementation of metaobject protocols which express this organization. No methodologies have been proposed for reflective programming per se. This paper proposes a first one aiming at the design of composable metaobjects. Given two independently developed reflective customizations, this methodology proposes principles to be observed in their design such that they can be composed using standard base-level aggregation or specialization. While this paper focuses on a simple MOP and illustrates the methodology on specific examples, this methodology can be generalized to other languages with different MOPs. For instance, we discuss how to adapt it to Clos. Keywords Composition, Aggregation, Specialization, Reflection, MetaObject Protocol, Metho...

People benefit from tightly integrated systems that can be designed, realized and evolved affordably. Unfortunately, common software design methods do not easily accommodate requirements for tightly integrated systems. Indeed, when used to meet such requirements, common methods tend to yield unnecessarily complex structures that complicate design and realization and that inhibit subsequent evolution. After substantiating this claim, I present the mediator method as a solution. This method combines behavioral entity-relationship (ER) modeling for design with a mediator approach to implementation. The mediator method is better than common methods for designing, realizing, and evolving many integrated systems. I support this claim both by rational argument from simplifying models and by careful...

Object-oriented programming consists of several different levels of abstraction, namely the algorithmic level, class level, cluster level, and system level. The testing of object-oriented software at the algorithmic and system levels is similar to conventional programming testing. Testing at the class and cluster levels poses new challenges. Since methods and objects may interact with one another dynamically with unforeseen combinations and invocations, they are much more complex to simulate and test than the static hierarchy of functional calls in conventional programs. In this paper, we propose a methodology for object-oriented software testing at the class and cluster levels. In class-level testing, it is essential to determine whether objects produced from the execution of implemented systems would preserve the properties defined by the specification, such as behavioral equivalence and non-equivalence. Our class-level testing methodology addresses both of these aspects. For the testing of behavioral equivalence, we propose to select fundamental pairs of equivalent ground terms as test cases using a black-box technique based on algebraic specifications, and then determine by means of a white-box technique whether the objects resulting from executing such test cases are observationally equivalent. To address the testing of behavioral non-equivalence, we have identified and analyzed several non-trivial problems in the current literature. We propose to classify term equivalence into four types, thereby setting up new concepts and deriving important properties. Based on these results, we propose an approach to deal with the problems in the generation of non-equivalent ground terms as test cases. Relatively little research has contributed to cluster-level testing. In this paper, we also discuss black-box testing at the cluster level. We illustrate the feasibility of using Contract, a formal specification language for the behavioral dependencies and interactions among cooperating objects of different classes in a given cluster. We propose an approach to test the interactions among different classes using every individual message-passing rule in the given Contract specification. We also present an approach to examine the interactions among composite message-passing rules. We have developed four testing tools to support our methodology.