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This thesis is a contribution to the corpus of workplace studies in the research field of computer-supported cooperative work. It reports on an in-house project to develop customisable groupware (software applications to support collaborative work) and to promote its use at 'GreenFam', an international, non-governmental organisation. This work was observed through a five year program of field research in order to study the methods used by developers in real-world groupware projects. The author initially took the role of participant observer on the project team as LOTUS NOTESTM was introduced to GreenFam's London centre. In the latter stages of research, an evaluation was carried out to report on the use of tools to support collaborative campaign work worldwide and to formulate guidelines for future developments. The field study is presented as three case histories, which track the course of the project. Case 1 looks at the rollout of a new email system, replacing THE COORDINATOR® software. The rollout is described as a competent practice of the IT developers that had evolved to implement customisable software organisation-wide. Case 2 looks at the first phase of the development of collaborative tools to support teams. It explores the difficulties experienced by the developers in realising GreenFam's vision of a more collaborative form of work and the limitations of their current practice. Case 3 describes the in situ evaluation, its methodology and the extent to which groupware tools and practices had evolved through use. Activity theory is employed as a critical method for the analysis of the case histories, focussing on change and the barriers to change in both the practices of developers and the appropriation of tools by users. The study found that during the course of the project the role of developer shifted from the specialised IT staff to 'facilitators', individuals who began to take responsibility for the ongoing development of collaborative tools to support their evolving use. It found a lack of appropriate design tools to support the development of collaborative systems, taking account of these changes in roles and the demands of the work. Further research is proposed, grounded in the study of the emergent roles of developers and the tools that are needed to support their work. A pattern language for modelling the design of common information spaces at GreenFam is described, as an example of the type of method that might be appropriate, and which could be used as an experimental tool in a program of further research. Keywords: activity theory, common information spaces, computer-supported cooperative work, evaluation, groupware, in-house development, pattern language, workplace study.

Distributed systems are increasingly being deployed in environments that range from small and tightly-coupled, such as wireless sensor networks, to large and loosely coupled, such as telecommunication systems. Middleware has emerged as a key technology in the construction of such systems, but middleware is increasingly required to be highly modular and configurable, to support separation of concerns between services, and, crucially, to support dynamic reconfiguration: i.e. to be capable of being changed while running. The goal of this thesis is to investigate, design and evaluate a novel approach to middleware-based dynamic reconfiguration that is based on the Aspect Orientation (AO) paradigm. In particular, the thesis proposes an aspect-oriented middleware platform called AO-OpenCom that builds AO-based reconfiguration on top of a dynamic component approach to middleware system composition. The goal is to support extremely flexible dynamic reconfiguration that can be applied both vertically and horizontally: i.e. at all levels of the system and uniformly across the distributed environment. The thesis also proposes a framework-based approach that supports consistent distributed dynamic reconfiguration to avoid problems that arise when reconfiguration operations are, for example, initiated concurrently or in the face of unstable infrastructure or involving contradictory compositions. The approach here is to define a model of potential threats to consistency and to introduce so-called 'threat aspects' that can be dynamically composed with the middleware platform to guard specifically against particular threats. Using dynamically-composed aspects both to realise dynamic reconfiguration and to guard against inconsistency lends simplicity and uniformity to the middleware. Furthermore, the design is recursive in that threat aspects can themselves be protected against other threats using the same approach. For example, a threat aspect addressing a security threat might be protected from security infrastructure crashes by being composed with a threat aspect that offers server replication. Inevitably, the ability to support dynamic reconfiguration and overcome reconfiguration inconsistency comes at the cost of an incurred performance overhead; hence; the thesis also investigates the impact of these overheads.

Many fault-tolerant group communication middleware systems have been implemented assuming crash failure semantics. While this assumption is not unreasonable, it becomes hard to justify when applications are required to meet high reliability requirements and are built using commercial off the shelf (COTS) components. This thesis implements new techniques to deal with Byzantine faults in a distributed group communication system. This thesis proposes a technique by which a process is duplicated into two replicas such that the process is turned into a self-checking pair with the two replicas communicating synchronously over a reliable network, but two different replicas from different processes can be connected asynchronously. The proposed approach is based on the replicas obeying state machine replication (SMR). SMR is utilised to assure signal-on-failure (fail-signal) semantics. One or both of the two replicas always issues a signal to other entities whenever there is a failure between and within the entities. This way, dependable activities such as group member failure detection, liveliness and security are removed from the upper layer of group communication service down to the two-replica pairs. With most of failure detection and security activities confined between the two replicas, semantics of a group communication are simplified and the number of phases and rounds of group communication protocols is reduced. The thesis demonstrates the fail-signalling concept by converting a group communication system member, through duplication of each group member, into a self checking pair. Security is augmented to the replicas' fail signalling capabilities to tolerate even more serious Byzantine faults. Performance results of the traditional group communication system are compared with results of a group system with duplicated fail signalling group members. The thesis has proven that the fail signalling group communication has the advantage of detecting failures faster without suspicions and that resulted in better group communication semantics, better dealing with member failures and faster formation of new group views.