2010 - 2019 Working Papers

Permanent URI for this collectionhttps://hdl.handle.net/10289/17947

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Now showing 1 - 20 of 41

Verification of the diagnosability of discrete-event systems in waters
(Department of Computer Science, The University of Waikato, 2018-11-21) McGrath, Nicholas
The task of detecting faults and reacting to them appropriately is a crucial aspect of a building a stable system. If a fault cannot be directly observed, its occurrence must be inferred from what can be observed. In the realm of discrete-event systems, the property of diagnosability has been defined, and several algorithms for testing diagnosability have been presented. Diagnosability relates to the ability for all possible faults to be correctly detected or inferred within a finite amount of time from their occurrence. WATERS (Waikato Analysis Toolkit for Events in Reactive Systems) is a software toolkit for the creation and analysis of discrete-event systems. In this report pre-existing existing algorithms for the verification of diagnosability and the implementation of one of these algorithms into WATERS are discussed. The created implementation can verify the diagnosability of a discrete-event system in polynomial time with respect to its state space and provide a counterexample if the discrete-event system was found to be not diagnosable.
Using augmented reality to enhance children’s books
(Department of Computer Science, The University of Waikato, 2018) Vanderschantz, Nicholas; Hinze, Annika; AL-Hashami, Aysha
This paper reports a case study on using Augmented Reality in children's books in which we explored the use of various types of interactions at different levels. The paper describes the design process and the insights gained through investigations into the requirements for enhancing children’s books with Augmented Reality. Using evidence from the literature along with our own observations, an interaction design model and resulting interface design are developed to explore interactivity in printed books using Augmented Reality. We report on an expert walk-through and discuss possible improvements and implications from our case study.
Framework and proofs for synthesis of least restrictive controllable supervisors for extended finite-state machines with variable abstraction
(Department of Computer Science, The University of Waikato, 2018) Malik, Robi; Teixeira, Marcelo
This working paper presents an algorithm that combines modular synthesis for extended finite-state machines (EFSM) with abstraction of variables by symbolic manipulation, in order to compute least restrictive controllable supervisors. Given a modular EFSM system consisting of several components, the proposed algorithm synthesises a separate supervisor for each specification component. To synthesise each supervisor, the algorithm iteratively selects components (plants and variables) from a synchronous composition until a least restrictive controllable solution is obtained. This improves on previous results of the authors where abstraction is only performed by the selection of components and not variables. The working paper explains the theory of EFSM synthesis and abstraction and includes formal proofs of all results. An example of a flexible manufacturing system illustrates how the proposed algorithm works to compute a modular supervisor.
The explicit conflict check algorithm implemented in the Waters library
(Department of Computer Science, The University of Waikato, 2018) Malik, Robi
This working paper describes the implementation of explicit model checking algorithms to verify the nonblocking or nonconflicting property of discrete event systems. Explicit algorithms enumerate and store all reachable states of a synchronous composition. Three alternatives optimised for memory consumption or runtime are described and compared. The algorithms have been implemented in C++ in the discrete event systems library Waters, and experimental results show that they can explore more than 100 million states on standard computers.
Use of mobile apps for teaching and research
(Department of Computer Science, The University of Waikato, 2017) Hinze, Annika; Vanderschantz, Nicholas; Timpany, Claire; Cunningham, Sally Jo; Saravani, Sarah-Jane; Wilkinson, Clive
Applications (apps) are software specifically designed for mobile de-vices. This paper reports on the results of an online survey about app use for teaching and research by students and academic staff at the University of Wai-kato. The questionnaire had 138 respondents. The results of the data analysis in-dicate that among respondents apps are primarily used for communication, data storage, and collaborative work. Nearly a third of respondents reported not using. any apps for academic purposes, with almost half that number citing a lack of knowledge about possible uses. In teaching practice, apps were reported to be used as a means to push information to students, e.g., for distributing reading materials and other teaching resources. In research, apps appeared to be used to self-organise, collaborate with other researchers, store information, and to stay current with research. This paper concludes with a list of implications.
Do internet search engines support children's search query construction: a visual analysis
(Department of Computer Science, The University of Waikato, 2017) Vanderschantz, Nicholas; Hinze, Annika
From previous studies into children's internet search practice, we gained insight into the taught strategies, children's behaviour and common errors while searching. This paper analyses the visual structure of commonly-used internet search engines (ISE) to explore how their interface and interaction design may influence the search practices of children. Common features of ISEs are identified and the effects of typical children's query construction on the visual presentation of information are reported. We use our observations to provide guidelines for the design and development of ISEs for children.
Compositional supervisor synthesis with state merging and transition removal
(Department of Computer Science, The University of Waikato, 2016) Mohajerani, Sahar; Malik, Robi; Fabian, Martin
This working paper proposes a framework to obtain memory-efficient supervisors for large discrete event systems, which are least restrictive, controllable, and nonblocking. The approach combines compositional synthesis and state-based abstraction with transition removal to mitigate the state-space explosion problem and reduce the memory requirements. Hiding and nondeterminism after abstraction are also supported. To ensure least restrictiveness after transition removal, the synthesised supervisor has the form of cascaded maps representing the safe states. These maps have lower space complexity than previous automata-based supervisors. The algorithm has been implemented in the DES software tool Supremica and applied to compute supervisors for several large industrial models. The results show that supervisor maps can be computed efficiently and in many cases require less memory than automata-based supervisors.
An algorithm for the synthesis of least restrictive controllable supervisors for extended finite-state machines
(Department of Computer Science, The University of Waikato, 2016) Malik, Robi; Teixeira, Marcelo
This working paper proposes an algorithm for the synthesis of modular supervisors using extended finite-state machines, i.e., state machines with variables and guards on the transitions. Synthesis is performed by iteratively selecting components from a synchronous composition until a least restrictive controllable solution is obtained. This method is usually faster and produces smaller supervisors than standard monolithic synthesis, while offering the modelling benefits of variables. An example of manufacturing system control illustrates the approach.
Classification and regression algorithms for WEKA implemented in Python
(University of Waikato, Department of Computer Science, 2015-10) Beckham, Christopher J.
WEKA is a popular machine learning workbench written in Java that allows users to easily classify, process, and explore data. There are many ways WEKA can be used: through the WEKA Explorer, users can visualise data, train classifiers and examine performance metrics; in the WEKA Experimenter, datasets and algorithms can be compared in an automated fashion; or, it can simply be invoked on the command-line or used as an external library in a Java project.
Investigating the use of activity trackers to observe high-risk work environments
(Department of Computer Science, The University of Waikato, 2015) Bowen, Judy; Hinze, Annika; Cunningham, Sally Jo; Parker, Richard
The New Zealand forestry industry has the country's highest rate of workplace fatalities. The reasons are not well studied or understood and no large-scale systematic physical and physiological data has been recorded to investigate this. Current research focusses on developing mechanised solutions and changing worker behaviour. We believe the first step in identifying any successful solution is to develop a fine-grained understanding of the physical context of forestry work by performing large-scale data collection of the levels of physical activity the workers engage in as well as their sleep patterns over extended periods of time. Our goal is to use lightweight, wearable technology (so-called activity trackers) to collect this data. In order to do so we need a clear understanding of the capabilities and limitations of such devices, both in general and in the proposed use environment for forestry workers. In this paper we present the results of user studies and comparisons of six activity trackers and three mobile phone applications used to track activity and sleep. We also discuss our initial pilot study with forestry workers and discuss the problems encountered using the trackers in the environment.
FSEA 2014 – Proceedings of the AVI 2014 Workshop on Fostering Smart Energy Applications through Advanced Visual Interfaces
(University of Waikato, Department of Computer Science, 2014) Masoodian, Masood; André, Elisabeth; Luz, Saturnino; Rist, Thomas
It is with great pleasure that we welcome you to FSEA 2014, the AVI 2014 workshop on Fostering Smart Energy Applications through Advanced Visual Interfaces. This workshop focuses on advanced interaction, interface, and visualization techniques for energy-related applications, tools, and services. It brings together researchers and practitioners from a diverse range of background, including interaction design, human-computer interaction, visualization, computer games, and other fields concerned with the development of advanced visual interfaces for smart energy applications. FSEA 2014 is the result of the efforts of many people involved in its organization, including our programme committee, and others who have assisted us in putting this workshop together.
Eliciting usage contexts of safety-critical medical devices
(Department of Computer Science, The University of Waikato, 2014) Bowen, Judy; Cunningham, Sally Jo; Hinze, Annika; Jung, Doris; Reeves, Steve
This position paper outlines our approach to improve the usage choice of suitable devices in different health care environments (contexts). Safety-critical medical devices are presumed to have undergone a thorough (user-centred) design process to optimize the device for the intended purpose, user group and environment. However, in real-life health care scenarios, actual usage may not reflect the original design parameters. We suggest the identification of further usage contexts for safety-critical medical devices through ethnographic and other studies, to assist better modelling of the challenges of different usage environments. In combination with system and interaction models, these context models can then be used for decision-support in choosing medical devices that are suitable for the intended environment.
Fully supervised training of Gaussian radial basis function networks in WEKA
(Department of Computer Science, The University of Waikato, 2014) Frank, Eibe
Radial basis function networks are a type of feedforward network with a long history in machine learning. In spite of this, there is relatively little literature on how to train them so that accurate predictions are obtained. A common strategy is to train the hidden layer of the network using k-means clustering and the output layer using supervised learning. However, Wettschereck and Dietterich found that supervised training of hidden layer parameters can improve predictive performance. They investigated learning center locations, local variances of the basis functions, and attribute weights, in a supervised manner. This document discusses supervised training of Gaussian radial basis function networks in the WEKA machine learning software. More specifically, we discuss the RBFClassifier and RBFRegressor classes available as part of the RBFNetwork package for WEKA 3.7 and consider (a) learning of center locations and one global variance parameter, (b) learning of center locations and one local variance parameter per basis function, and (c) learning center locations with per-attribute local variance parameters. We also consider learning attribute weights jointly with other parameters.
Tracking battery state-of-charge in a continuous use off-grid electricity system
(University of Waikato, Department of Computer Science, 2013-10) Apperley, Mark; Alahmari, Mohammed Mushabab
The growing importance of batteries in the delivery of primary energy, for example in electric vehicles and isolated off-grid electricity systems, has added weight to the demand for simple and reliable measures of a battery’s remaining stored energy at any time. Many approaches to estimating this battery state-of-charge exist, ranging from those based on a full appreciation of the chemistry and physics of the storage and delivery mechanisms used, and requiring extensive data on which to base an estimate, to the naïve and simple, based only, for example, on the terminal voltage of the battery. None, however, is perfect, and able to deliver a simple percentage-full figure, as in a fuel gauge. The shortcomings are due to a range of complicating factors, including the impact of rate of charge, rate of discharge, battery aging, and temperature, to name just some of these. This paper presents a simple yet effective method for tracking state-of-charge in an off-grid electricity system, where batteries are in continuous use, preventing static parameter measurements, and where charge/discharge cycles do not necessarily follow an orderly sequence or pattern. A reliable indication of state-of-charge is, however, highly desirable, but need be only of fuel gauge precision, say to the nearest 12-20%. The algorithm described utilises knowledge of the past, and constantly adapts parameters such as charge efficiency and total charge capacity based on this knowledge, and on the occurrence of specific identifiable events such as zero or full charge.
Catching and displaying memory cues for a mobile augmented memory system
(University of Waikato, Department of Computer Science, 2013-12) Bellamy, Jake; Hinze, Annika
This report goes over and details the progress of the 2013 COMP477 project “Augmenting Memory: The Digital Parrot on Mobile Devices” undertaken by Jake Bellamy and supervised by Annika Hinze at the University of Waikato. The report begins with an overview on the problem with remembering events in people’s lives and details the background information on the Digital Parrot system. It also describes the previous project that preceded this one, which began to conceptualize the Digital Parrot on mobile devices. It analyses problems with the current design of the system and addresses them. The report then goes on to conduct an in depth user study with the functioning version of the software. The user study finds design flaws and incorrect functionality in the application that would not have otherwise been apparent. Finally, the report concludes with a proposed user interface concept that addresses all of the issues found in the user study and describes how the system would work. It describes the initial implementation that has begun in building this system.
Text categorization and similarity analysis: similarity measure, architecture and design
(University of Waikato, Department of Computer Science, 2013-12) Fowke, Michael; Hinze, Annika; Heese, Ralf
This research looks at the most appropriate similarity measure to use for a document classification problem. The goal is to find a method that is accurate in finding both semantically and version related documents. A necessary requirement is that the method is efficient in its speed and disk usage. Simhash is found to be the measure best suited to the application and it can be combined with other software to increase the accuracy. Pingar have provided an API that will extract the entities from a document and create a taxonomy displaying the relationships and this extra information can be used to accurately classify input documents. Two algorithms are designed incorporating the Pingar API and then finally an efficient comparison algorithm is introduced to cut down the comparisons required.
Text categorization and similarity analysis: similarity measure, literature review
(University of Waikato, Department of Computer Science, 2013-12) Fowke, Michael; Hinze, Annika; Heese, Ralf
Document classification and provenance has become an important area of computer science as the amount of digital information is growing significantly. Organisations are storing documents on computers rather than in paper form. Software is now required that will show the similarities between documents (i.e. document classification) and to point out duplicates and possibly the history of each document (i.e. provenance). Poor organisation is common and leads to situations like above. There exists a number of software solutions in this area designed to make document organisation as simple as possible. I'm doing my project with Pingar who are a company based in Auckland who aim to help organise the growing amount of unstructured digital data. This reports analyses the existing literature in this area with the aim to determine what already exists and how my project will be different from existing solutions.
Social interactions using an electronic rabbit
(University of Waikato, Department of Computer Science, 2013-12) Zaicu, Alexandru Calin; Hinze, Annika
In this project we use an electronic rabbit called Karotz, created by French company Violet. The rabbits have the ability to connect autonomously to a WI-FI network. IN this project we use Karotz to record an audio log that will contain sounds of the environment. We also programmed a way for the rabbit to send audio to its other Karotz friend. We explored if Karotz can be used to help people stay in contact with each other and to feel less homesick.
Text categorization and similarity analysis: implementation and evaluation
(University of Waikato, Department of Computer Science, 2013-12) Fowke, Michael; Hinze, Annika; Heese, Ralf
This report covers the implementation of software that aims to identify document versions and se-mantically related documents. This is important due to the increasing amount of digital information. Key criteria were that the software was fast and required limited disk space. Previous research de-termined that the Simhash algorithm was the most appropriate for this application so this method was implemented. The structure of each component was well defined with the inputs and outputs constant and the result was a software system that can have interchangeable parts if required.
The orienting mouse: An input device with attitude
(University of Waikato, Department of Computer Science, 2013-11) Apperley, Mark; Rogers, Bill
This paper presents a modified computer mouse, the Orienting Mouse, which delivers orientation as an additional dimension of input; when the mouse is moved on a flat surface it reports, in addition to the conventional x, y translation, angular rotation of the device in the x, y plane. The orienting mouse preserves important properties of the standard mouse; all measurements are relative and movement is tracked only while the mouse is on its flat surface. If the user lets go of the mouse, leaving it on the surface, its position and orientation do not change until it is touched again. Picking the mouse up and putting it down in a different orientation leaves the angle and position unchanged. While the concept of sensing mouse rotation is not new, our work focuses on movement and navigation in 3D, rather than on precision positioning tasks. We describe a number of sample applications developed to test its effectiveness in this context. Specific features exploited and described include (i) an algorithm for calculating the mouse angle which cancels drift between the two sensors, and (ii) the use of angular gearing which avoids unnatural and uncomfortable hand positions when moving through large angles; informal user testing validates this idea.

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