Search

Model-based languages such as MATLAB/Simulink play an essential role in the model-driven development of software systems. To comply with new requirements, it is common practice to create new variants by copying existing systems and modifying them. Commonly referred to as clone-and-own, severe problems arise in the long-run when no dedicated variability management is installed. To allow for a documented and structured reuse of systems, their variability information needs to be reverse-engineered. In this paper, we propose an advanced comparison procedure, the Matching Window Technique, and a customizable metric. Both allow us to overcome structural alterations commonly performed during clone-and-own. We analyze related MATLAB/Simulink models and determine, classify and represent their variability information in an understandable way. With our technique, we assist model engineers in maintaining and evolving existing variants. We provide three feasibility studies with real-world models from the automotive domain and show our technique to be fast and precise. Furthermore, we perform semi-structured interviews with domain experts to assess the potential applicability of our technique in practice.

This report documents the program and the outcomes of Dagstuhl Seminar 18182 "Software Business, Platforms, and Ecosystems: Fundamentals of Software Production Research".

Product-line architectures, i.e. a software architecture and component set shared by a family of products, represents a promising approach to achieving reuse of software. Several companies are initiating or have recently adopted a product-line architecture. However, little experience is available with respect to the evolution of the products, the software components and the software architecture. Due to the higher level of interdependency between the various software assets, software evolution is a more complex process. In this paper, we discuss the results of two case studies concentrating on the evolution of software assets in two swedish organizations that have employed the product-line architecture approach for several years. Based on these two cases, we discuss the commonalities, presented as categorizations of the evolution of the requirements, the software architecture and the software components, and also the differences between the two cases. Published in an edited form as: Mikael Svahnberg, Jan Bosch, Evolution in Software Product Lines: Two Cases, in Journal of Software Maintenance - Research and Practice 11(6), pp. 391-422, 1999.

The software architecture plays an important role in achieving a modifiable system, but few methods for modifiability analysis exist. In this paper, we propose an analysis method for software architecture modifiability that has successfully been applied in several cases. The method consists of five main steps, i.e. goal selection, software architecture description, scenario elicitation, scenario evaluation and interpretation.

Modifiability is an important quality for software systems, because a large part of the costs associated with these systems is spent on modifications. The effort, and therefore cost, that is required for these modifications is largely determined by a system’s software architecture. Analysis of software architectures is therefore an important technique to achieve modifiability and reduce maintenance costs. However, few techniques for software architecture analysis currently exist. Based on our experiences with software architecture analysis of modifiability, we have developed an analysis method consisting of five steps. In this paper we report on our experiences with this method. We illustrate our experiences with examples from two case studies of SAA of modifiability. These case studies concern a system for mobile positioning at Ericsson Software Techology and a system for freight handling at DFDS Fraktarna. Our experiences are related to each step of the analysis process. In addition, we made some observations on SAA of modifiability in general. Beskriver erfarenheterna från två fall studier. submitted for publication at HICSS conference.

Object-oriented application frameworks present one of the most successful approaches to developing reusable assets in industry, but developing frameworks is both difficult and expensive. Framework generally evolve to maturity through a number of iterations due to the incorporation of new requirements and better domain understanding. Since changes to frameworks have a large impact due to the effects on the applications build based on the asset, it is important to assess the maturity of a framework. Bansiya [3, 4] presents an approach to assessing framework maturity based on a set of design metrics and formulates four statements. In this paper, we present the results of a replicated case study of the framework maturity assessment approach. Our study subject consists of four successive versions of a proprietary black-box application framework. Our findings partly support the statements formulated in the original study, but differ in some places. The differences are discussed and explanations and argumentation provided.

Scenario profiles are used increasingly often for the assessment of quality attributes during the architectural design of software systems. However, the definition of scenario profiles is subjective and no data is available on the effects of individuals on scenario profiles. In this paper we present the design, analysis and results of a controlled experiment on the effect of individuals on scenario profiles, so that others can replicate the experiments on other projects and people. Both scenario profiles created by individuals and by groups are studied. The findings from the experiment showed that groups with prepared members proved to be the best method for creating scenario profiles. Unprepared groups did not perform better than individuals when creating scenario profiles.

Product-line architectures present an important approach to increasing software reuse and reducing development cost by sharing an architecture and set of reusable components among a family of products. However, evolution in product-line architectures is more complex than in traditional software development since new, possibly conflicting, requirements originate from the existing products in the product-line and new products that are to be incorporated. In this paper, we present a case study of product-line architecture evolution. Based on the case study, we develop categorizations for the evolution of requirements, the product-line architecture and product-line architecture components. Subsequently, we analyze and present the relations between these categorizations.

Product-line architectures present an important approach to increasing software reuse and reducing development cost by sharing an architecture and set of reusable components among a family of products. However, evolution in product-line architectures is more complex than in traditional software development since new, possibly conflicting, requirements originate from the existing products in the product-line and new products that are to be incorporated. In this paper, we present a case study of product-line architecture evolution. Based on the case study, we develop categorizations for the evolution of requirements, the product-line architecture and product-line architecture components. Subsequently, we analyze and present the relations between these categorizations.

Object-oriented framework technology has become a common reuse technology in object-oriented software development. As with all software, frameworks tend to evolve. Once the framework has been deployed, new versions of a framework cause high maintenance cost for the products built with the framework. This fact in combination with the high costs of developing and evolving an object-oriented framework make it important to have controlled and predictable evolution of the framework?s functionality and costs. We present three methods 1) Evolution Identification Using Historical Information, 2) Stability Assessment and 3) Distribution of Development Effort which have been applied to between one to three different frameworks, both in the proprietary and commercial domain. The methods provide management with information which will make it possible to make well-informed decisions about the framework?s evolution, especially with respect to the following issues; identification of evolution-prone modules, framework deployment, change impact analysis, benchmarking and requirements management. Finally, the methods are compared to each other with respect to costs and benefits.

In method-based software development, software engineers create artifacts based on the heuristic rules of the adopted method. Most CASE tools, however, do not actively assist software engineers in applying the heuristic rules. To provide an active support, the rules must be formalized, implemented and integrated within the framework of current CASE tools. In this paper we describe an approach for formalizing the heuristic rules of methods.

There are many similarities between industrial goods manufacturing and software development processes. This paper first briefly analyzes the recent developments in goods manufacturing, and then identifies the equivalent techniques in software technology. It is claimed that products developed during software manufacturing must be modeled as active artifacts. As a possible approach in this direction, an object-oriented artifact production framework is presented and evaluated.

Reuse of software has been one of the main goals of software engineering for decades. Reusing software is not simple and most efforts resulted in small reusable, black-box components. With the emergence of the object-oriented paradigm, the enabling technology for reuse of larger components became available and resulted in the definition of object-oriented frameworks. Frameworks attracted attention from many researchers and software engineers and frameworks have been defined for a large variety of domains. The claimed advantages of frameworks are, among others, increased reusability and reduced time to market for applications. Although several examples have shown these advantages to exist, there are problems and hindrances associated with frameworks that may not appear before their usage in real projects. The authors have been involved in the design, maintenance and usage of several object-oriented frameworks and based on the experiences from these projects, a number of problems related to frameworks are descr ibed. The problems are organised according to four categories, i.e. framework development, usage, composition and maintenance. For each category, the most relevant problems and experiences are presented. This paper may help software engineers to avoid the described problems, whereas researchers may try to address these topics in their research.

The conventional object-oriented paradigm provides client-server message passing as the primary means of interaction between objects. Although this is appropriate in situations where one objects requests a service from another object, there are other situations where one object, the observer, depends on state-changes or actions occurring at another object, the target. In those situations, the object-oriented paradigm requires the target object to notify the observer objects, despite the fact that the target object does not benefit from the interaction. This inverted interaction scheme leads to problems such as increased coupling and decreased understandability, maintainability and reusability of the resulting classes. In the analysis of object interactions one can identify four roles: the benefitor, the establisher, the sender and the receiver. The aforementioned problems result from the fact that in client-server interaction, the benefitor and the sender are not always the same object. To address this, we pr opose the notion of causal connections, an alternative interaction mechanism complementing the traditional client-server interaction. Two implementations of causal connections are described; one in the context of C++ and another using the layered object model. It is shown that causal connections solve the problems mentioned above.

Measurement systems are of increasing importance for manufacturing, due to high automation level of production processes. Although most measurement systems have much in common and are expensive to construct, these systems are often developed from scratch, hardly reusing the available designs and implementations. To address this, we have designed and implemented an object-oriented framework for the domain of measurement systems that can be used as the core of measurement systems. Evaluations of the framework show that it captures the main concepts in the domain and that the required extensions for individual applications are limited. In this paper, a number of example framework instantiations are presented. The lessons we learned during the framework design and an evaluation of the object-oriented modelling paradigm are presented.

Design patterns have proven to be useful for the design of object-oriented systems. The power of a design pattern lies in its ability to provide generic solutions that can be specialised for particular situations. The implementation of design patterns has received only little attention and we have identified two relevant problems associated with the implementation. First, the traceability of a design pattern in the implementation is often insufficient; often the design pattern is `lost'. Second, implementing design patterns may present significant implementation overhead for the software engineer. Often, a, potentially large, number of simple methods has to be implemented with trivial behaviour, e.g. forwarding a message to another object. In this paper, the layered object model (LayOM) is presented. LayOM provides language support for the explicit representation of design patterns in the programming language. LayOM is an extended object-oriented language in that it contains several components that are not pa rt of the conventional object model, such as states, categories and layers. Layers are used to represent design patterns at the level of the programming language and example layer types for four design patterns are presented. LayOM is supported by a development environment that translates LayOM code into C++. The generated C++ code can be used as any C++ code for the development of applications. An important aspect of LayOM is that the language itself is extensible. This allows new design patterns to be added to the language model.

The requirements on real-time systems are changing. Traditionally, reliability and predictability of, especially hard, real-time systems were the main requirements. This lead to systems that were stand-alone, embedded and static. Future real-time systems, but also current systems, still require reliability and predictability, but also distribution of the real-time system, integration with non real-time systems and the ability to dynamically change the components of the system at runtime. Traditional approaches to real-time system development have difficulties in addressing these additional requirements. Therefore, new ways of constructing real-time systems have to be explored. In this article, we develop a real-time object-oriented model that facilitates the requirements of flexibility without sacrificing the predictability, integration and dynamicity aspects.

During the last years, one can recognise a development towards application domain languages and extensible language models. Due to their extended expressiveness, these language models have considerable advantages over rigid general purpose languages. However, a complicating factor in the use of extensible language models are the conventional compiler construction techniques. Compilers constructed using these techniques often are large entities that are highly complex, difficult to maintain and hard to reuse. As we have experienced, these characteristics clearly complicate extending existing compilers. As a solution to this, we developed an alternative approach to compiler construction is proposed, based on object-oriented principles. The approach is based on delegating compiler objects (dcos) that provide a structural decomposition of compilers in addition to the conventional functional decomposition. The dco approach supports modularisation and reuse of compiler specifications, such as lexer and parser speci fications. We constructed an integrated tool set, letos, implementing the functionality of delegating compiler objects.

Large object-oriented systems have, at least, four characteristics that complicate object communication, i.e the system is distributed and contains large numbers, e.g. thousands, of objects, objects need to be reallocated at run-time and objects can be replaced by other objects in order to adapt to the dynamic changes in the system. Traditional object communication is based on sending a message to a receiver object known to the sender of the message. At linking or instantiation time, an object establishes its acquaintances through name/class-based binding and uses these objects through its life time. If this is too rigid, the software engineer has to implement the binding of objects manually using pointers. In our experiments we found the traditional acquaintance communication semantics too limited and we identified several problems, related to the reusability of objects and selection mechanisms, understandability and expressiveness. We recognised that it is important to separate a class or object's requirements on its acquaintances from the way an object selects and binds its acquaintances in actual systems. Based on this observation, we studied the required expressiveness for acquaintance handling and identified four relevant aspects: type and duration of binding, conditions for binding, number of selected objects and selection region for binding. To implement these aspects, we defined acquaintance layers as part of the layered object model. Acquaintance layers uniformly extend the traditional object-oriented acquaintance handling semantics and allow for the first-class representation of acquaintance selection and binding, thereby increasing traceability and reusability.

Traditionally, finite state machines based approaches are used in real-time object-oriented systems development for modelling the dynamic behaviour of an object. Finite state machines based approaches, however, suffer from several problems when used for modelling large and complex objects. As an alternative, an extended object model, LayOM, and an associated modelling approach is proposed aiming to solve the aforementioned problems and other problems related to object state.

Conventional compilers often are large entities that are highly complex, difficult to maintain and hard to reuse. In this article it is argued that this is due to the inherently functional approach to compiler construction. An alternative approach to compiler construction is proposed, based on object-oriented principles, which solves (or at least lessens) the problems of compiler construction. The approach is based on delegating compiler objects (DCOs) that provide a structural decomposition of compilers in addition to the conventional functional decomposition. The DCO approach makes use of the parser delegation and lexer delegation techniques, that provide reuse and modularisation of syntactical, respectively, lexical specifications.

In this paper, a number of problems of conventional automated software engineering support environments are described. These problems are related to the functional approach these environments take, the lack of initiative these systems exhibit and the causal connection gap between design information and the operational entity. As an alternative, we suggest an autonomous agent approach. Each artifact is modelled as an autonomous agent that is responsible for its own development. Artifacts are organised in specialisation hierarchies which can be traversed by agents. As a consequence, the methodology needs to be inverted, i.e. specified from the artifact's perspective rather than from the software engineer's perspective.

Conventional grammar specification and parsing is generally done in a monolithic manner, i.e. the syntax and semantics of a grammar are specified in one large specification. Although this might be sufficient in static environments, a modular approach is required in situations where the syntax or semantics of a grammar specification are subject to frequent changes. The problems with monolithic grammars are related to (1) dealing with the complexity, (2) extensibility and (3) reusability. We propose the concept of {\em parser delegation} as a solution to these problems. Parser delegation allows one to modularise and reuse grammar specifications. To achieve this, the notion of a production rule is specialised into (1) overriding, (2) extending and (3) delegating production rule types. To experiment with parser delegation, we have developed D-yacc, a graphical tool for defining grammars. Parser delegation has been applied for constructing a translator for an experimental language and is currently applied in other domains.

Programming languages and software engineering methods are highly related in that both are images of an underlying paradigm. In this paper we investigate the role of the paradigm, the language model and the software development method and define requirements on each of the three concepts. Subsequently, we describe the {\em layered object model}, an extended object model which allows for first-class representation of relations between objects and constraints on the behaviour of an object, and discuss how it achieves {\em paradigm extensibility}, i.e. extensibility of the paradigm and the supporting language model.

Although object-oriented methods make extensive use of relations between objects, these relations, other than inheritance and part-of, can not directly be represented by the conventional object-oriented model. This means that relations which are identified during analysis and design have to be implemented on top of the object model, i.e. by using method code and message passing, rather than by expressing relations directly within in the model. It would be beneficial if the object-oriented model would support the specification of all relevant types of relations within the model, including application-domain specific relation types. Therefore, we propose a mechanism, implemented in LayOM -- an extended object model, that supports the specification of all types of relations between objects within the model as components of the object model. In addition, an approach for identifying and specifying application-domain relation types is presented.

Recent research shows runtime architectural reflection is instrumental in, for instance, building adaptive and flexible systems or checking correspondence between design and implementation. Moreover, experience with computational reflection in various branches of computer science shows that the interface through which the meta-information of the running system is accessed, and possibly modified, lies at the heart of designing reflective systems. This paper proposes that such an interface should be like a database: accessed through queries expressed using the concepts with which architecture is described. Specifically, our contributions are: (1) a presentation of the general idea of a query-based approach to architectural reflection, (2) a definition of an Architectural Query Language (AQL) in which perspectives on an architectural model can be expressed as queries, (3) a prototype of a system which both creates runtime models of specific distributed architectures and allow for evaluation of AQL queries on these models. We illustrate the viability of the approach in two particular applications of such a model: constraint checking relative to an architectural style, and reasoning about certain quality attributes of an architecture.

WCOP 2000, held in conjunction with ECOOP 2000 in Sophia Antipolis, France, was the fifth workshop in the successful series of workshops on component-oriented programming. The previous workshops were held in conjunction with the respective ECOOP conferences in Linz, Austria, Jyväskylä, Finland, Brussels, Belgium and Lisbon, Portugal. WCOP96 had focused on the principal idea of software components and worked towards definitions of terms. In particular, a high-level definition of what a software component is was formulated. WCOP97 concentrated on compositional aspects, architecture and gluing, substitutability, interface evolution, and non-functional requirements. WCOP98 had a closer look at issues arising in industrial practice and developed a major focus on the issues of adaptation. WCOP'99 moved on to address issues of component frameworks, structured architecture, and some bigger systems built using components frameworks. The topics for WCOP 2000 focused on component composition, validation and refinement and the use of component technology in the software industry.

This report presents the results of a course on software product lines. The assignment in the course was to develop a software product line. . During the course, the students had to develop the following artifacts in groups: product line architecture, component designs, product derivations, modifiability assessment and a prototype. The results of the course are described in this report