This thesis was written by Stein Eldar Johnsen beginning 15th August 2003 and delivered by 1st September 2005 with Svein Erik Bratsberg as mentor. The main topics are consistency and distributed hash tables. One unsolved problem with distributed hash tables is consistent lookup. Various DHTs can show acceptable consistency ratings, but no DHT can show no lookup inconsistency during churn. We chose to use a structural prevention strategy to remove inconsistent lookup on the basis that inconsistent lookups are a result of inconsistency in routing tables. We define consistent lookup as a lookup that returns a correct membership state from some time during lookup. Churn and especially unplanned membership changes may cause series of inconsistency problems if not handled carefully. The combination of a planned membership change (e.g. join) and an unplanned membership change (e.g. node crash causing a node to leave) can cause problems needing careful repairing in the systems routing tables. Table changes are necessary done in an order that guarantees a consistent view over index ownership, and makes the possibility of consistent termination at any point during execution. Other novel solutions include fail-fast disconnected-detection, locking membership protocols and pre-join knowledge propagation. All these solutions are shown to improve consistency through analysis, and are easily adapted for ring geometry DHTs. Accord was design to test many of the proposals made in the analysis. We built a distributed hash table infrastructure (with no hash table functionality), that used membership protocols based on the analysis results. The two main membership protocols were based on a 2-level 2-phase commit protocol for join, and simple 2-phase commit with distributed operations from a single coordinator for the leave protocol. The solutions proposed in this thesis are fit for all ring geometry DHTs, and some may be adapted for tree geometry DHTs, and some for all DHTs. All of Chord, Bamboo andPastry are good DHTs that can be used for testing the proposals, where all or most solutions are shown to be possible. Future work includes more testing, simulations and analysis of adaptations for different geometries.

This thesis have looked at two subjects that are a necessary part of a Location Based Service. Guidelines on how to make a Location Model of the campus has been suggested. The proposed model enhanced already existing suggestions and provides support for different queries. Testing was done with Ekahau WLAN positioning technology to obtain location information. The results of the testing showed that the technology was suitable to provide a services that required accuracy at room-level. Services that required a finer grained location estimate where not feasible.

Numerous standardisation and integration initiatives within the use of information and communication technologies (ICT) seem to fail due to lack of acknowledging the socio-technical negotiation that goes into standardisation work. This thesis addresses the implication of open standards development within organisational use of ICT. A standardisation initiative for data transmission, the PRODML project, within the domain of the Oil & Gas industry is investigated. This initiative strives to increase interoperability between organisations as it focus on removing the use of proprietary standards. By using Actor-Network Theory, this thesis try to articulate how such standards emerge, and the critical factors that can lead to their success. It emphasis the need to consider the importance of aligning interests in standards development, and the importance of creating the right initial alliance, building an installed base, for increased credibility and public acceptance.

The project behind this thesis empirically explored the possibility of mobile handheld devices and use situations of the hospital arena by building prototypes and have them evaluated by real users in realistic settings. The main aspects of discussion are: what characterizes work that is suitable in this context; how well does the technology support the user’s work ―input of data, output of data, navigation, ease of handling, and general usability of device; and what the ideal mobile device in a hospital would be.

This thesis focuses on the effect of nursing staff's redundant work routines on error and quality of care in one Critical Access Hospital in rural Wisconsin, USA. Methods were based on participatory design and an ethnographic approach, and included individual interviews and observation-based interviews. Introduction of a computerized information system was scheduled for the case study site and this thesis makes pre-implementation suggestions regarding staff training, interface features desired by the future users, and removal or restructuring of certain redundancies. The contribution of this thesis to information systems research is a classification system for determining the degree of redundancy (productive, gray-zone, and unproductive) present in the task chains of specific work routines, and a second classification system for determining to what extent modifying or removing an unproductive redundancy returns value. The degree to which an unproductive redundancy may be modified or removed is weighted against the difficulty of changing the work routines associated with that redundancy as well as the expected impact on other routines.

This thesis concerns the safety in user interfaces. In particular it concerns the user interfaces in systems in which safety is critical. I have studied such systems in the maritime industry, where we for instance may find them on the bridges of ships. Computer systems get more and more important in the daily routines of humans, and it is important that this does not go unnoticed. Designers of computer systems need to take human factors into consideration when designing their systems. These considerations might be especially important in complex systems, as these are often safety critical. The bridges on ships are likely to include complex systems for the operator to handle, as they often involve multiple screens, or other factors that increase the complexity of a system. Such factors might include being able to pay attention to several incidents at once. When dealing with complex systems, it is important that the operator knows how to handle the system, and also how to react when an incident occurs. These are factors that need to be considered by the designer when making the system and theories on how to do this are described in the thesis. I have also described standards which consider this, like the ISO 11064 standard, or the Atomos regulation and the ISO 17894 which considers this for the maritime industry in particular. Parts of the industry have made an effort to develop tools to be used to improve the safety. I have studied some of these efforts and presented them in the thesis. Furthermore, I have developed a survey to study how the individual members and different parts of the industry feel and behave towards safety. The survey gave an insight into reality of how safety is being handled in the industry as a whole. In particular it pointed to the main problem of the maritime industry, that the industry is very heterogeneous, and also that the different parts of the industry are in competition with each other. Most of the respondents had not heard about the Atomos regulation or the ISO 17894 standards, efforts that could have been used as a tool to improve the level of safety. The questionnaire also showed that while most of the respondents are satisfied with the level of safety in their organization, they are not satisfied with the level of safety in the overall industry. The thesis consists of six parts. Part I deals with the introduction and general theory from research methods and psychology. Part II deals with usability and related standards. These include ISO 11064, theory on usability and a description of an accident due to poorly designed user interface. Part III describes relevant background from the maritime industry, which involves the ISO 17894 standard, the Atomos regulation and e-navigation, an example of a newly made effort. Part IV gives a description of the development of my questionnaire, and also provides the results and conclusions made from them. Part V provides the conclusions and suggestions for future work, while part VI contains appendices.

Exception handling suffers from a fluke in its evolution. Some time in the 1970's, a researcher called Goodenough introduced the exception handling mechanism, known today as the tcode{try...catch} construct. At about the same time, two fellows called Parnas and Würges published a paper about "undesired events". This paper appears forgotten. The funny thing is, Parnas and Würges effectively described how to emph{use} exception handling mechanisms. There is a need to respond to this undesired event. Exception handling suffers from lack of design guidelines and a number of inconsistencies with the object-oriented paradigm, among other things. The thesis' main contribution is creating a library of exception challenges and the evaluation of safety facades, an approach that introduce an architecture and guidelines for designing exception handling. Through qualitative evaluation, this thesis shows how safety facades form an interesting new approach to exception handling.

When proponents of open source software are asked to explain the success of their movement they typically point to the quality of the software produced, which is in turn attributed to the rather unconventional development model of releasing unfinished versions of the software and having users look over the code and report and fix bugs. This thesis investigates the open source quality assurance model from a knowledge management perspective – based on the assumption that debugging involves a high degree of knowledge work. By doing interpretive case studies of two open source projects – using direct observation, e-mail archives, and bug-trackers as data sources – I present descriptive accounts of the day to day quality practices in open source development. The analysis shows that conceptualizing and classifying bugs is a complex process involving sense-making and subjective considerations; that the peer-review process in open source projects has a lot in common with traditional field-testing; and that communication tools and mediums are used interchangeably, but with certain preferences depending on subject matter. I conclude that perhaps the success of the open source development model is not due to its novelty compared to traditional software engineering, but because open source developers have recognized that debugging is a knowledge-intensive process. Keywords: Open Source, Software Quality, Knowledge Management

As our reliance on software has increased, robustness has become an important subject. Software that is not robust enough may lead to frustration, or loss of time or value. Software architecture forms the main structures of applications. Having focus on the quality of an applications architecture may increase the robustness of the application. This thesis tries to find a suitable architectural process for achieving robustness. I report on the findings from ten interviews with software architects from the software industry, around the theme robustness. Interview results are used in order to form a definition of robustness which is wider than the definitions I found in literature. The thesis's main contribution is a proposed process for designing and analyzing robust software architectures that make use of elements from existing methods. The proposed process is grounded on results from interviews, personal experience, and evaluation of existing methods in literature.

Agile software development have in recent years been widely accepted in industry, as well as being the target of much research. XP has been the main focus, while there exist relatively few studies of other Agile methods such as Scrum. This thesis describe an ethnographic study of a Scrum team in a project. The goal is to give a rich description of the use and application of Scrum. Special attention is given to the implications of differences in implementation from theory. Another focus is to reveal the dynamics of teamwork within the project. The main findings are that Scrum was easy to implement, and worked well, but is challenging when used to increase predictability. With regard to teamwork, Scrum supported a shared mental, communication and adaptability. The leadership function is however complex, and requires good interpersonal skills. Keywords: Agile, Scrum, Teamwork, Implementation, Software development, Software engineering