Oliver Stiemerling

How to make software softer—designing tailorable applications

The design of tailorable systems is an important issue for fields of application which are characterized by differentiation and dynamics. We show how tailorability can be combined with approaches of evolutionary and participative software-engineering and discuss some conceptual problems arising from this approach. Moreover, we present two case studies on how to design tailorable functionality in a groupware development project.

Component-Based Approaches to Tailorable Systems

Flexibility is one of the most striking features of modern software. As the idea of integrating components is easily understood by programmers as well as end users, component architectures seem to be very promising to serve as a technological basis. In this paper we give an overview of our work in the last years. A component model called FLEXIBEANS has been designed with the special notion to develop highly flexible and tailorable applications. The FREEVOLVE platform then serves as an environment in which compositions can be run and tailored. The second part of the paper deals with the development and evaluation of different tailoring environments in which end users can compose their own applications or tailor existing ones. Users tests showed that besides a coherent technical basis and a manageable visual tailoring environment, there is a need for additional support techniques. We discuss how techniques to support users’ individual and collective tailoring activities can be integrated into the user interface.

Tailorable component architectures for CSCW-systems

Tailorability is generally regarded as a key property of CSCW systems, because cooperative activities provide for very dynamic and diversified requirements. Extensive tailorability has to be supported by the design of the system architecture. We investigate the value of component architectures for this purpose and discuss several design options for the questions raised by this approach. We propose a model of a component architecture, which supports tailoring activities by changing parameter settings of single components, changing the composition of components, and changing the implementation of components. Hierarchical composition of components allows for tailoring operations on different levels of abstraction and complexity. We introduce the concepts of tailoring constraints, tailoring constructs, and tailoring rights, which allow a controlled evolution of the system. Finally, we show how our approach can be employed to design a tailorable application.

The use of cooperation scenarios in the design and evaluation of a CSCW system

Design and evaluation of groupware systems raise questions which do not have to be addressed in the context of single user systems. The designer has to take into account not only the interaction of a single user with the computer, but also the computer-supported interaction of several users with each other. In this article we describe the use of cooperation scenarios in the design and evaluation of an innovative access control system for a concrete groupware application developed in the PoLITeam project. We have used informal textual scenarios to capture a rich description of the particularities of access to cooperatively used documents in three different organizations. Based on these scenarios, we have developed an access control system, which not only allows specification of access rights in advance but also allows involvement of third persons at the actual time of access, using negotiation and notification mechanisms. We describe our evaluation strategy which again employs the cooperation scenarios developed in the empirical phase. After relating our approach to other work, we summarize and discuss our experiences and the advantages (and disadvantages) of using scenarios for the design and evaluation of computer systems cooperative work (CSCW) systems. Finally, we give a brief outlook on future work.

The EVOLVE project: component-based tailorability for CSCW applications

Tailorability is generally regarded as a key property of groupware systems owing to the dynamics and differentiation of cooperative work. This article investigates the use of software components as a generic architectural concept for designing tailorable groupware applications. First, the issues raised by this approach are discussed in the context of an exploratory experiment during which component-based tailorability was applied to a real tailoring problem in thePoliTeam project. The experiments results led us to concentrate on questions concerning the support of distributed CSCW applications. As a consequence, we have developed theEvolve platform, whose design concepts are described. Furthermore, a concrete example for the application of the approach to the design of a tailorable distributed coordination tool is given. We discuss related work, summarise the current state of the component-based tailorability approach and propose venues of further research.

The Evolve tailoring platform: supporting the evolution of component-based groupware

Groupware systems are designed to support the cooperation of people within and between enterprises. The development of groupware using component-based programming techniques has received a lot of attention recently. The commonly expected benefits are reduced development time, lower costs and higher product quality. Aiming at an additional benefit, the work presented in this paper makes use of the concept of software components after development in order to provide tailorability of already-deployed groupware systems. We describe the architecture of the Evolve platform, which permits one to maintain and manipulate nested component structures of distributed groupware systems at run-time. Apart from run-time tailorability, the architecture meets other groupware-specific (or relevant) requirements, namely support for synchronous and asynchronous cooperative tailoring, tailoring at different levels of complexity, and the flexible control of the scope of tailoring activities (i.e. the set of users affected by these activities). Evolve itself is application-independent and works with any set of software components complying with the FlexiBeans component model, which is an adaptation of the JavaBeans model. We demonstrate the object-oriented design behind Evolve with a simple example and give an overview of related and future work.

Distributed component-based tailorability for CSCW applications

Tailorability is generally regarded as a key property of groupware systems due to the dynamics and diversity of cooperative work. This article investigates the use of software components as a generic architectural concept for designing tailorable groupware applications. First, the issues raised by this approach are discussed. The results of a first exploratory, experiment led us to concentrate on the support of distributed tailorable CSCW applications. We discuss the question of an appropriate component model and develop requirements for a platform for the flexible deployment of distributed component-based applications. As a consequence of these reflections, we have developed the FLEXIBEANS component model and the EVOLVE platform whose design principles are described. Furthermore, an application example using the approach to design a tailorable distributed coordination tool is given. Finally, we summarize and propose venues of further research.

Tailoring Groupware for Different Scopes of Validity

Tailorability is generally regarded as a key requirement for groupware applications. In this paper, we focus on a specific class of tailoring activities: the definition of different system behaviour for specific scopes of validity. Since the state of the art in Computer Supported Cooperative Work (CSCW) does not yet offer any satisfactory solutions to support users in performing this class of tailoring activities, we develop an approach based on tailoring statements, which are similar to production rules. We show how inconsistencies resulting from contradictory statements can be handled either automatically or by involving the affected users. We present a prototype which implements our approach to tailorability in a commercial groupware system, using access control as an example for the proposed class of tailoring activities. Finally, we present the results of a usability test carried out which employs the thinking aloud method.

Beyond "Yes or No" - Extending Access Control in Groupware with Awareness and Negotiation

We present three scenarios concerning access to documents in three real world fields of application, which have in common that they are very difficult to support with classical anticipative access control systems. We show, how - based on a highly configurable notification and negotiation service, which is tightly integrated with a classical access control system - the common permission and denial options can be extended with awareness and negotiation and how this approach supports the three initial access scenarios. We also introduce our implementation of the notification and negotiation service in the PoliTeam project.

Web-Services als Basis für evolvierbare Softwaresysteme

Web-service-technologies are often regarded as the dominant way of software development in the future, especially for inter-company scenarios. While the current discussion in this area focuses mainly on the integration of software, this paper takes the next step and looks at the evolvability of the system resulting from the integration. A system’s adaptability in the face of changing requirements is usually the decisive success factor in industrial environments.This paper analyses experiences with a large, web-service-based application already in industrial use. As principal result we show that such a web-service-architecture indeed has the potential to support the evolvability of a complex software system. The clear separation of system components achieved by web-services — not only on a conceptual, but also on a technological and organizational level — is especially beneficial for large, long-term software projects that span company boundaries. The decision for a web-service-architecture requires additional efforts in the design, development and deployment of the software. With these additional efforts in mind, the concluding discussion offers some guidelines for web-service-projects, especially concerning the sensible (and economical) decomposition of the system into components connected by webservices.This contribution draws on experiences from a portal project for a large German company. The project employed around 50 persons including all sub- and partner-projects. For reasons of confidentiality the name of the company and project details are omitted, albeit without hurting the main points of the paper.