A Graphical Environment Supporting the Algebraic Specification of Abstract Data Types

Abstract Data Types (ADTs) are a powerful conceptual and practical device for building high-quality software because of the way they can describe objects whilst hiding the details of how they are represented within a computer. In order to implement ADTs correctly, it is first necessary to precisely describe their properties and behaviour, typically within a mathematical framework such as algebraic specification. These techniques are no longer merely research topics but are now tools used by software practitioners. Unfortunately, the high level of mathematical sophistication required to exploit these methods has made them unattractive to a large portion of their intended audience. This thesis investigates the use of computer graphics as a way of making the formal specification of ADTs more palatable. Computer graphics technology has recently been explored as a way of making computer programs more understandable by revealing aspects of their structure and run-time behaviour that are usually hidden in textual representations. These graphical techniques can also be used to create and edit programs. Although such visualisation techniques have been incorporated into tools supporting several phases of software development, a survey presented in this thesis of existing systems reveals that their application to supporting the formal specification of ADTs has so far been ignored. This thesis describes the development of a prototype tool (called VISAGE) for visualising and visually programming formally-specified ADTs. VISAGE uses a synchronised combination of textual and graphical views to illustrate the various facets of an ADT's structure and behaviour. The graphical views use both static and dynamic representations developed specifically for this domain. VISAGE's visual programming facility has powerful mechanisms for creating and manipulating entire structures (as well as their components) that make it at least comparable with textual methods. In recognition of the importance of examples as a way of illustrating abstract concepts, VISAGE provides a dedicated tool (called the PLAYPEN) that allows the creation of example data by the user. These data can then be transformed by the operations belonging to the ADT with the result shown by means of a dynamic, graphical display. An evaluation of VISAGE was conducted in order to detect any improvement in subjects' performance, confidence and understanding of ADT specifications. The subjects were asked to perform a set of simple specification tasks with some using VISAGE and the others using manual techniques to act as a control. An analysis of the results shows a distinct positive reaction from the VISAGE group that was completely absent in the control group thereby supporting the thesis that the algebraic specification of ADTs can be made more accessible and palatable though the use of computer graphic techniques

User interfaces and discrete event simulation models.

A user interface is critical to the success of any computer-based system. Numerous studies have shown that interface design has a significant influence on factors such as learning time, performance speed, error rates, and user satisfaction. Computer-based simulation modelling is one of the domains that is particularly demanding in terms of user interfaces. It is also an area that often pioneers new technologies that are not necessarily previously researched in terms of human-computer interaction. The dissertation describes research into user interfaces for discrete event simulation. Issues that influence the 'usability' of such systems are examined. Several representative systems were investigated in order to generate some general assumptions with respect to those characteristics of user interfaces employed in simulation systems. A case study was carried out to gain practical experience and to identify possible problems that can be encountered in user interface development. There is a need for simulation systems that can support the developments of simulation models in many domains, which are not supported by contemporary simulation software. Many user interface deficiencies are discovered and reported. On the basis of findings in this research, proposals are made on how user interfaces for simulation systems can be enhanced to match better the needs specific to the domain of simulation modelling, and on how better to support users in simulation model developments. Such improvements in user interfaces that better support users in simulation model developments could achieve a reduction in the amount of time needed to learn simulation systems, support retention of learned concepts over time, reduce the number of errors during interaction, reduce the amount of time and effort needed for model development, and provide greater user satisfaction

Mixed physical and virtual design environments for digital fabrication

Digital Fabrication (3D printing, laser-cutting or CNC milling) enables the automated fabrication of physical objects from digital models. This technology is becoming more readily available and ubiquitous, as digital fabrication machines become more capable and affordable. When it comes to designing the objects that are to be fabricated however, there are still barriers for novices and inconveniences for experts. Through digital fabrication, physical objects are created from digital models. The digital models are currently designed in virtual design environments, which separates the world we design in from the world we design for. This separation hampers design processes of experienced users and presents barriers to novices. For example, manipulating objects in virtual spaces is difficult, but comes naturally in the physical world. Further, in a virtual environment, we cannot easily integrate existing physical objects or experience the object we are designing in its future context (e.g., try out a game controller during design). This lack of reflection impedes designer's spatial understanding in virtual design environments. To enable our virtual creations to become physical reality, we have to posses an ample amount of design and engineering knowledge, which further steepens the learning curve for novices. Lastly, as we are physically separated from our creation - until it is fabricated - we loose direct engagement with the material and object itself, impacting creativity. We follow a research through design approach, in which we take up the role as interaction designers and engineers. Based on four novel interaction concepts, we explore how the physical world and design environments can be brought closer together, and address the problems caused their prior separation. As engineers, we implement each of these concepts in a prototype system, demonstrating that they can be implemented. Using the systems, we evaluate the concepts and how the concepts alleviate the aforementioned problems, and that the design systems we create are capable of producing useful objects. In this thesis, we make four main contributions to the body of digital fabrication related HCI knowledge. Each contribution consists of an interaction concept which addresses a subset of the problems, caused by the separation of virtual design environment, and physical target world. We evaluate the concepts through prototype implementations, example walkthroughs and where appropriate user-studies, demonstrating how the concepts alleviate the problems they address. For each concept and system, we describe the design rationale, and present technical contributions towards their implementation. The results of this thesis have implications for different user audiences, design processes, the artifacts users design and domains outside of digital fabrication. Through our concepts and systems, we lower barriers for novices to utilize digital fabrication. For experienced designers, we make existing design processes more convenient and efficient. We ease the design of artifacts that reuse existing objects, or that combine organic and geometrically structured design. Lastly, the novel interaction concepts (and on a technical level, the systems) we present, which blur the lines between physical and virtual space, can serve as basis for future interaction design and HCI research

Design Characterization for Black-and-White Textures in Visualization

We investigate the use of 2D black-and-white textures for the visualization of categorical data and contribute a summary of texture attributes, and the results of three experiments that elicited design strategies as well as aesthetic and effectiveness measures. Black-and-white textures are useful, for instance, as a visual channel for categorical data on low-color displays, in 2D/3D print, to achieve the aesthetic of historic visualizations, or to retain the color hue channel for other visual mappings. We specifically study how to use what we call geometric and iconic textures. Geometric textures use patterns of repeated abstract geometric shapes, while iconic textures use repeated icons that may stand for data categories. We parameterized both types of textures and developed a tool for designers to create textures on simple charts by adjusting texture parameters. 30 visualization experts used our tool and designed 66 textured bar charts, pie charts, and maps. We then had 150 participants rate these designs for aesthetics. Finally, with the top-rated geometric and iconic textures, our perceptual assessment experiment with 150 participants revealed that textured charts perform about equally well as non-textured charts, and that there are some differences depending on the type of chart

GRAPHICAL ONE-TIME PASSWORD AUTHENTICATION

Complying with a security policy often requires users to create long and complex passwords to protect their accounts. However, remembering such passwords appears difficult for many and may lead to insecure practices, such as choosing weak passwords or writing them down. One-Time Passwords (OTPs) aim to overcome such problems; however, most implemented OTP techniques require special hardware, which not only adds costs, but also raises issues regarding availability. This type of authentication mechanism is mostly adopted by online banking systems to secure their clients’ accounts. However, carrying around authentication tokens was found to be an inconvenient experience for many customers. Not only the inconvenience, but if the token was unavailable, for any reason, this would prevent customers from accessing their accounts securely. In contrast, there is the potential to use graphical passwords as an alternative authentication mechanism designed to aid memorability and ease of use. The idea of this research is to combine the usability of recognition-based and draw-based graphical passwords with the security of OTP. A new multi-level user-authentication solution known as: Graphical One-Time Password (GOTPass) was proposed and empirically evaluated in terms of usability and security aspects. The usability experiment was conducted during three separate sessions, which took place over five weeks, to assess the efficiency, effectiveness, memorability and user satisfaction of the new scheme. The results showed that users were able to easily create and enter their credentials as well as remember them over time. Eighty-one participants carried out a total of 1,302 login attempts with a 93% success rate and an average login time of 24.5 seconds. With regard to the security evaluation, the research simulated three common types of graphical password attacks (guessing, intersection, and shoulder-surfing). The participants’ task was to act as attackers to try to break into the system. The GOTPass scheme showed a high resistance capability against the attacks, as only 3.3% of the 690 total attempts succeeded in compromising the system.King Abdulaziz City for Science and Technolog

The A.D.E. taxonomy of spreadsheet application development

Spreadsheets are a major application in end-user computing, one of the fastest growing areas of computing. Studies have shown that 30% of spreadsheet applications contain errors. As major decisions are often made with the assistance of spreadsheets, the control of spreadsheet applications is a matter of concern to enduser developers, managers, EDP auditors and computer professionals. The application of appropriate controls to the spreadsheet development process requires prior categorisation of the spreadsheet application. The special-purpose A.D.E. (Application, Development, Environment) taxonomy of spreadsheet application development was evolved by mathematical taxonomic methods to categorise spreadsheet development projects to facilitate their management and control

Applying touch gesture to improve application accessing speed on mobile devices.

The touch gesture shortcut is one of the most significant contributions to Human-Computer Interaction (HCI). It is used in many fields: e.g., performing web browsing tasks (i.e., moving to the next page, adding bookmarks, etc.) on a smartphone, manipulating a virtual object on a tabletop device and communicating between two touch screen devices. Compared with the traditional Graphic User Interface (GUI), the touch gesture shortcut is more efficient, more natural, it is intuitive and easier to use. With the rapid development of smartphone technology, an increasing number of data items are showing up in users’ mobile devices, such as contacts, installed apps and photos. As a result, it has become troublesome to find a target item on a mobile device with traditional GUI. For example, to find a target app, sliding and browsing through several screens is a necessity. This thesis addresses this challenge by proposing two alternative methods of using a touch gesture shortcut to find a target item (an app, as an example) in a mobile device. Current touch gesture shortcut methods either employ a universal built-in system- defined shortcut template or a gesture-item set, which is defined by users before using the device. In either case, the users need to learn/define first and then recall and draw the gesture to reach the target item according to the template/predefined set. Evidence has shown that compared with GUI, the touch gesture shortcut has an advantage when performing several types of tasks e.g., text editing, picture drawing, audio control, etc. but it is unknown whether it is quicker or more effective than the traditional GUI for finding target apps. This thesis first conducts an exploratory study to understand user memorisation of their Personalized Gesture Shortcuts (PGS) for 15 frequently used mobile apps. An experiment will then be conducted to investigate (1) the users’ recall accuracy on the PGS for finding both frequently and infrequently used target apps, (2) and the speed by which users are able to access the target apps relative to GUI. The results show that the PGS produced a clear speed advantage (1.3s faster on average) over the traditional GUI, while there was an approximate 20% failure rate due to unsuccessful recall on the PGS. To address the unsuccessful recall problem, this thesis explores ways of developing a new interactive approach based on the touch gesture shortcut but without requiring recall or having to be predefined before use. It has been named the Intelligent Launcher in this thesis, and it predicts and launches any intended target app from an unconstrained gesture drawn by the user. To explore how to achieve this, this thesis conducted a third experiment to investigate the relationship between the reasons underlying the user’s gesture creation and the gesture shape (handwriting, non-handwriting or abstract) they used as their shortcut. According to the results, unlike the existing approaches, the thesis proposes that the launcher should predict the users’ intended app from three types of gestures. First, the non-handwriting gestures via the visual similarity between it and the app’s icon; second, the handwriting gestures via the app’s library name plus functionality; and third, the abstract gestures via the app’s usage history. In light of these findings mentioned above, we designed and developed the Intelligent Launcher, which is based on the assumptions drawn from the empirical data. This thesis introduces the interaction, the architecture and the technical details of the launcher. How to use the data from the third experiment to improve the predictions based on a machine learning method, i.e., the Markov Model, is described in this thesis. An evaluation experiment, shows that the Intelligent Launcher has achieved user satisfaction with a prediction accuracy of 96%. As of now, it is still difficult to know which type of gesture a user tends to use. Therefore, a fourth experiment, which focused on exploring the factors that influence the choice of touch gesture shortcut type for accessing a target app is also conducted in this thesis. The results of the experiment show that (1) those who preferred a name-based method used it more consistently and used more letter gestures compared with those who preferred the other three methods; (2) those who preferred the keyword app search method created more letter gestures than other types; (3) those who preferred an iOS system created more drawing gestures than other types; (4) letter gestures were more often used for the apps that were used frequently, whereas drawing gestures were more often used for the apps that were used infrequently; (5) the participants tended to use the same creation method as the preferred method on different days of the experiment. This thesis contributes to the body of Human-Computer Interaction knowledge. It proposes two alternative methods which are more efficient and flexible for finding a target item among a large number of items. The PGS method has been confirmed as being effective and has a clear speed advantage. The Intelligent Launcher has been developed and it demonstrates a novel way of predicting a target item via the gesture user’s drawing. The findings concerning the relationship between the user’s choice of gesture for the shortcut and some of the individual factors have informed the design of a more flexible touch gesture shortcut interface for ”target item finding” tasks. When searching for different types of data items, the Intelligent Launcher is a prototype for finding target apps since the variety in visual appearance of an app and its functionality make it more difficult to predict than other targets, such as a standard phone setting, a contact or a website. However, we believe that the ideas that have been presented in this thesis can be further extended to other types of items, such as videos or photos in a Photo Library, places on a map or clothes in an online store. What is more, this study also leads the way in tackling the advantage of a machine learning method in touch gesture shortcut interactions

A formalism for describing and simulating systems with interacting components.

This thesis addresses the problem of descriptive complexity presented by systems involving a high number of interacting components. It investigates the evaluation measure of performability and its application to such systems. A new description and simulation language, ICE and it's application to performability modelling is presented. ICE (Interacting ComponEnts) is based upon an earlier description language which was first proposed for defining reliability problems. ICE is declarative in style and has a limited number of keywords. The ethos in the development of the language has been to provide an intuitive formalism with a powerful descriptive space. The full syntax of the language is presented with discussion as to its philosophy. The implementation of a discrete event simulator using an ICE interface is described, with use being made of examples to illustrate the functionality of the code and the semantics of the language. Random numbers are used to provide the required stochastic behaviour within the simulator. The behaviour of an industry standard generator within the simulator and different methods of number allocation are shown. A new generator is proposed that is a development of a fast hardware shift register generator and is demonstrated to possess good statistical properties and operational speed. For the purpose of providing a rigorous description of the language and clarification of its semantics, a computational model is developed using the formalism of extended coloured Petri nets. This model also gives an indication of the language's descriptive power relative to that of a recognised and well developed technique. Some recognised temporal and structural problems of system event modelling are identified. and ICE solutions given. The growing research area of ATM communication networks is introduced and a sophisticated top down model of an ATM switch presented. This model is simulated and interesting results are given. A generic ICE framework for performability modelling is developed and demonstrated. This is considered as a positive contribution to the general field of performability research

Elimination of doubt : methods for a predictive design to direct and optimize the flow of visitors

Ympäristömme globaalistuu ja monimutkaistuu kaiken aikaa. Prosessi näkyy muun muassa kansainvälisen liikenteen solmukohdissa. Esimerkiksi lentokentät ovat kyseisiä eri kulttuurien keskinäisen vuorovaikutuksen kohtia. Eri kulttuureista tulevien ihmisten pitää osata orientoitua vieraassa ja usein sekavassa ympäristössä. Jotta toiminta olisi sujuvaa näissä solmukohdissa, on suunnistamiseen tarvittavan tiedon oltava nopeasti omaksuttavaa ja ymmärrettävää. Monet muotoilijat ja suunnittelijat ajattelevat, että opastejärjestelmät ovat reduktionistisia ja mekanistisia syy-seuraus systeemejä. On kuitenkin ilmeistä, että kansainvälisesti harmonisoimattomien piktogrammien kyky välittää informaatiota on epäonnistunutta. Nykyiset kognitiotieteen havainnot osoittavat, että visuaalisen havaitsemisen ja tilallisen orientaation aikaisemmat mallit ovat vain osittain toimivia. Siispä oli syytä kysyä ”onko mahdollista tuottaa ennakoiva malli jonka avulla voi kehittää, toteuttaa ja varmistaa suunnitteluratkaisuja, jotka ohjaavat ja optimoivat vierailijoiden virtaa laajoissa julkisissa tiloissa.“ Tutkimuksen keskiössä on tästä syystä tilallisessa orientoitumisessa tapahtuva kulttuurinen merkityksellistäminen ja paikkatietoisuuden lisääminen (situation awareness). Juuri tuo yksilöllinen merkityksen tuottaminen voi tarkoittaa laajaa kirjoa erilaisia tulkintoja. Paikkatietoisuuden syntymisen erilaiset mahdollisuudet yhdessä erilaisten menetelmien kanssa voivat tuottaa ratkaisuja suunnitteluprosessiin. Suunnitteluprosessissa voidaan ottaa huomioon myös havaintopsykologisia näkökulmia. Kaiken kaikkiaan tämä johtaa systeemis-holistiseen ja käyttäjäkeskeiseen ajatteluun julkisten tilojen opastejärjestelmien suunnittelun kehityksessä. Esitän myös käytännöllisen ratkaisun opastejärjestelmien suunnitteluun ja arviointiin tarkastelemalla olemassa olevien järjestelmien rakennetta ja parametreja sekä niiden kehitystyötä. Työ sisältää yhteensä yhdeksän tapaustarkastelua. Tutkimusmenetelminä käytin laadullista havainnointia ja kvantitatiivista analyysiä. Havainnoin ja tulkitsin etnisiä tottumuksia ja henkilökohtaisia näkemyksiä. Tekemäni kyselyjen perusteella näyttää siltä, että konstruoimaani mallia voitaisiin käyttää kehittämisen ja todentamisen välineenä.The rapid development of international traffic characterizes our increasingly globalized and ever more complex world. Nodal points (for example, airports) have formed where people from various cultural backgrounds and with differing levels of educational attainment need to reorient themselves in a unfamiliar and often confusing environment. A key condition to ensure everything works smoothly in such an international junction is the extremely fast reception and processing of information by everyone involved. The dominant school of thought among many designers and planners of guidance and routing systems is still a reductionist and mechanistic one (cause - effect). It has become apparent that the use of non-internationally harmonized pictograms as information carriers has failed completely. Recent findings in the field of cognitive science demonstrate convincingly that previous models of visual perception and spatial orientation can only highlight partial aspects. For these aspects, the question has arisen: “Is there a possibility to evolve a predictive system to develop, implement and verify design solutions to direct and optimize the flow of visitors in large public spaces?” Therefore, the moment of semiosis of the orientation seekers moved into the focus of the investigation. This moment of meaning-making, which is perceived by every individual differently, spans the entire spectrum of the perception of the designated item (the optical characteristic of the character substrate) between manifold interpretation or absolute certainty. The various viewing options of “situational awareness” with the help of various methodologies provide solutions for the design process. Taking the aspects of perceptual psychology into account leads to the development of a systemic/holistic and user-centred design of orientation systems in public spaces. Identifying and consulting the predictive parameters in a systematic process could show a practicable solution for the planning and evaluation of guidance and routing systems. In various national and international case studies, the process reliability and processing quality of this solution were demonstrated. Involving mixed research methodologies of qualitative observation and quantitative analysis, it was possible to develop a workable model. Through observation and interpretation, ethnic habits and personal views were taken into account to develop the methods. The use of questionnaires or surveys created statistics to prove or disprove the hypothetical model. The capacity of the presented model and the operationalization of the research demonstrated an effective method for overcoming barriers of age, language and culture. The publication satisfies, therefore, the criteria of the academic quality of a practice-based Ph.D