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Publication Atomic components(Working Paper, University of Waikato, Department of Computer Science, 2004-02) Reeves, Steve; Streader, DavidThere has been much interest in components that combine the best of state-based and event-based approaches. The interface of a component can be thought of as its specification and substituting components with the same interface cannot be observed by any user of the components. Here we will define the semantics of atomic components where both states and event can be part of the interface. The resulting semantics is very similar to that of (event only) processes. But it has two main novelties: one, it does not need recursion or unique fixed points to model nontermination; and two, the behaviour of divergence is modelled by abstraction, i.e. the construction of the observational semantics.Publication Unifying state and process determinism(Working Paper, University of Waikato, Department of Computer Science, 2004-02) Reeves, Steve; Streader, DavidIf a coin is given to a deterministic robot that interacts with a deterministic vending machine then is the drink that the robot is delivered determined? Using process definitions of determinism from CSP, CCS or ACP the answer is "no", whereas state-based definitions of determinism can reasonably be construed as giving the answer "yes". In order to unify what we see as discrepancies in state- and action-based notions of determinism we will consider process algebras over two sets of actions: the active or casual actions of the robot and the passive or reactive actions of the vending machine. In addition we will add priority to the actions and when two τ actions are possible then the τ action with the highest priority will be executed.Publication The syntax and semantics of μ-Charts(Working Paper, University of Waikato, Department of Computer Science, 2004-02) Reeve, Greg; Reeves, Steveμ-Charts is a language for specifying the behaviour of reactive systems. The language is a simplified variant of the well-known language Statecharts that was introduced by Harel. Development of the μ-Charts language is ongoing research undertaken under the auspices of the Formal Methods Laboratory of the Computer Science Department, University of Waikato. This paper gives a comprehensive treatment of the syntax and semantic for μ-Charts.Publication DeepDocument: use of a multi-layered display to provide context awareness in text editing(Working Paper, University of Waikato, Department of Computer Science, 2004-02) Masoodian, Masood; McKoy, Sam; Rogers, Bill; Ware, DavidThe most commonly used view in word processing software shows only the paragraphs of text immediately adjacent to the cursor position. Generally this is appropriate, for example when composing a single paragraph. However, when reviewing or working on the layout of a document it is necessary to establish awareness of current text in the context of the document as a whole. This can be done by scrolling or zooming, but when doing so, focus is easily lost and hard to regain. Furthermore, in a collaborative editing/review setting it is not only necessary for each user to understand their own context, but also to have an awareness of the contexts of the other participants. Although systems have been developed that provide awareness in collaborative settings, they usually rely on multiple windows, which use valuable screen real-estate. We have developed a system called DeepDocument using a two-layered LCD display in which both focussed and document-wide views are presented simultaneously. The overview is shown on the rear display and the focussed view on the front, maintaining full screen size for each. The physical separation of the layers takes advantage of human depth perception capabilities to allow users to perceive the views independently without having to redirect their gaze. DeepDocument has been written as an extension to Microsoft Word™. It also includes awareness features to track focus positions for both single and multiple users.Publication Ensembles of nested dichotomies for multi-class problems(Working Paper, University of Waikato, Department of Computer Science, 2004-02) Frank, Eibe; Kramer, StefanNested dichotomies are a standard statistical technique for tackling certain polytomous classification problems with logistic regression. They can be represented as binary trees that recursively split a multi-class classification task into a system of dichotomies and provide a statistically sound way of applying two-class learning algorithms to multi-class problems (assuming these algorithms generate class probability estimates). However, there are usually many candidate trees for a given problem and in the standard approach the choice of a particular tree is based on domain knowledge that may not be available in practice. An alternative is to treat every system of nested dichotomies as equally likely and to form an ensemble classifier based on this assumption. We show that this approach produces more accurate classifications than applying C4.5 and logistic regression directly to multi-class problems. Our results also show that ensembles of nested dichotomies produce more accurate classifiers than pairwise classification if both techniques are used with C4.5, and comparable results for logistic regression. Compared to error-correcting output codes, they are preferable if logistic regression is used, and comparable in the case of C4.5. An additional benefit is that they generate class probability estimates. Consequently they appear to be a good general-purpose method for applying binary classifiers to multi-class problems.Publication "Please turn ON your mobile phone" - first impressions of text-messaging in lectures(Working Paper, University of Waikato, Department of Computer Science, 2004-05) Jones, Matt; Marsden, GaryPrevious work by Draper and Brown investigated the use of specialized handsets in increate interactivity in lecture settings. Inspired by their encouraging findings we have been exploring the use of conventional mobile phones and text-messaging to allow students to communicate with the lecturer as the class proceeds. In our pilot-study, students were able to respond to MCQs and send free-text comments and questions to the lecturer via SMS. Through observations and interviews with students and lecturers, we gained useful impressions of the value of such an approach. Students enjoyed the opportunity to be more actively involved but voiced concerns about costs.Publication Analyzing library collections with starfield visualizations(Working Paper, Department of Computer Science, 2004-01-01) Sánchez, J. Alfredo; Twidale, Michael B.; Nichols, David M.; Silva, Nabani N.This paper presents a qualitative and formative study of the uses of a starfield-based visualization interface for analysis of library collections. The evaluation process has produced feedback that suggests ways to significantly improve starfield interfaces and the interaction process to improve their learnability and usability. The study also gave us clear indication of additional potential uses of starfield visualizations that can be exploited by further functionality and interface development. We report on resulting implications for the design and use of starfield visualizations that will impact their graphical interface features, their use for managing data quality and their potential for various forms of visual data mining. Although the current implementation and analysis focuses on the collection of a physical library, the most important contributions of our work will be in digital libraries, in which volume, complexity and dynamism of collections are increasing dramatically and tools are needed for visualization and analysis.Publication Design and analysis of an efficient distributed event notification service(Working Paper, Department of Computer Science, University of Waikato, 2004-01-01) Bittner, Sven; Hinze, AnnikaEvent Notification Services (ENS) use the publish/subscribe paradigm to continuously inform subscribers about events they are interested in. Subscribers define their interest in so-called profiles. The event information is provided by event publishers, filtered by the service against the profiles, and then send to the subscribers. In real-time systems such as facility management, an efficiency filter component is one of the most important design goals. In this paper, we present our analysis and evaluation of efficient distributed filtering algorithms. Firstly, we propose a classification and first-cut analysis of distributed filtering algorithms. Secondly, based on the classification we describe our analysis of selected algorithms. Thirdly, we describe our ENS prototype DAS that includes three filtering algorithms. This prototype is tested with respect to efficiency, network traffic and memory consumption. In this paper, we discuss the results of our practical analysis in detail.Publication Bayesian network classifiers in Weka(Working Paper, Department of Computer Science, 2004-09-01) Bouckaert, Remco R.Various Bayesian network classifier learning algorithms are implemented in Weka [10].This note provides some user documentation and implementation details. Summary of main capabilities: _Structure learning of Bayesian networks using various hill climbing (K2, B, etc) and general purpose (simulated annealing, tabu search) algorithms. _Local score metrics implemented; Bayes, BDe, MDL, entropy, AIC. _Global score metrics implemented; leave one out cv, k-fold cv and cumulative cv. _Conditional independence based causal recovery algorithm available. _Parameter estimation using direct estimates and Bayesian model averaging. _GUI for easy inspection of Bayesian networks. _Part of Weka allowing systematic experiments to compare Bayes net performance with general purpose classi_ers like C4.5, nearest neighbor, support vector, etc. _Source code available under GPL allows for integration in other systems and makes it easy to extend.Publication Language switching in a digital library; does it make a difference if the default language is set to Maori?(Working Paper, 2004-01-01) Keegan, Te Taka Adrian Gregory; Cunningham, Sally Jo; Don, Katherine J.In this paper we investigate the effect of default interface language on usage patterns of the Niupepa digital library (a collection of historic Māori language newspapers), by switching the default interface language between Māori and English in alternate weeks. Transaction analysis of the Niupepa collection logs indicates that changing default language affects the length of user sessions and the number of actions within sessions, and that the English language interface was used most frequently.Publication Open issues in semantic query optimization in relational DBMS(Working Paper, Department of Computer Science, University of Waikato, 2004-01-01) Genet, Bryan Howard; Hinze, AnnikaAfter two decades of research into Semantic Query Optimization (SQO) there is clear agreement as to the efficacy of SQO. However, although there are some experimental implementations there are still no commercial implementations. We first present a thorough analysis of research into SQO. We identify three problems which inhibit the effective use of SQO in Relational Database Management Systems(RDBMS). We then propose solutions to these problems and describe first steps towards the implementation of an effective semantic query optimizer for relational databases.Publication Usability discussions in open source development(Working Paper, Department of Computer Science, 2004-01-01) Nichols, David M.; Twidale, Michael B.The public nature of discussion in open source projects provides a valuable resource for understanding the mechanisms of open source software development. In this paper we explore how open source projects address issues of usability. We examine bug reports of several projects to characterise how developers address and resolve issues concerning user interfaces and interaction design. We discuss how bug reporting and discussion systems can be improved to better support bug reporters and open source developers.Publication Event notification services: analysis and transformation of profile definition languages(Working Paper, Department of Computer Science, University of Waikato, 2004-01-01) Jung, Doris; Hinze, AnnikaThe integration of event information from diverse event notification sources is, as with meta-searching over heterogeneous search engines, a challenging task. Due to the complexity of profile definition languages, known solutions for heterogeneous searching cannot be applied for event notification. In this technical report, we propose transformation rules for profile rewriting. We transform each profile defined at a meta-service into a profile expressed in the language of each event notification source. Due to unavoidable asymmetry in the semantics of different languages, some superfluous information may be delivered to the meta-service. These notifications are then post-processed to reduce the number of spurious messages. We present a survey and classification of profile definition languages for event notification, which serves as basis for the transformation rules. The proposed rules are implemented in a prototype transformation module for a Meta-Service for event notification.Publication Mining data streams using option trees (revised edition, 2004)(Working Paper, Department of Computer Science, The University of Waikato, 2004-01-01) Holmes, Geoffrey; Kirkby, Richard Brendon; Pfahringer, BernhardThe data stream model for data mining places harsh restrictions on a learning algorithm. A model must be induced following the briefest interrogation of the data, must use only available memory and must update itself over time within these constraints. Additionally, the model must be able to be used for data mining at any point in time. This paper describes a data stream classi_cation algorithm using an ensemble of option trees. The ensemble of trees is induced by boosting and iteratively combined into a single interpretable model. The algorithm is evaluated using benchmark datasets for accuracy against state-of-the-art algorithms that make use of the entire dataset.