Frameworks for Enhancing Temporal Interface Behaviour through Software Architectural Design Devina Ramduny-Ellis A thesis submitted in partial fulfilment of the requirements of Staffordshire University for the degree of Doctor of Philosophy December 2002 Abstract Frameworks for Enhancing Temporal Interface Behaviour through Software Architectural Design Devina Ramduny-Ellis A thesis submitted in partial fulfilment of the requirements of Staffordshire University for the degree of Doctor of Philosophy December, 2002 The work reported in this thesis is concerned with understanding aspects of temporal behaviour. A large part of the thesis is based on analytical studies of temporal properties and interface and architectural concerns. The main areas covered include: (i) analysing long-term human processes and the impact of interruptions and delays (ii) investigating how infrastructures can be designed to support synchronous fast pace activity (iii) design of the Getting-to-Know (GtK) experimental notification server The work is motivated by the failure of many collaborative systems to effectively manage the temporal behaviour at the interface level, as they often assume that the interaction is taking place over fast, reliable local area networks. However, the Web has challenged this assumption and users are faced with frequent network-related delays. The nature of cooperative work increases the importance of timing issues. Collaborative users require both rapid feedback of their own actions and timely feedthrough of other actions. Although it may appear that software architectures are about the internals of system design and not a necessary concern for the user interface, internal details do show up at the surface in non-functional aspects, such as timing. The focus of this work is on understanding the behavioural aspects and how they are influenced by the infrastructure. The thesis has contributed to several areas of research: (a) the study of long-term work processes generated a trigger analysis technique for task decomposition in HCI (b) the analysis of architectures was later applied to investigate architectural options for mobile interfaces (c) the framework for notification servers commenced a design vocabulary in CSCW for the implementation of notification services, with the aim of improving design (d) the impedance matching framework facilitate both goal-directed feedthrough and awareness In particular, (c) and (d) have been exercised in the development of the GtK separable notification server. i Acknowledgements I would like to thank my supervisor, Alan Dix, for his guidance and support throughout the duration of this research. His critical comments on drafts of this thesis have been invaluable. I would also like to share this achievement with my parents and parents-in-laws who have been wondering what I have been doing for so many years. Finally, a special thank you to my husband, Geoffrey, for his patience and encouragement. I am also very grateful for his useful suggestions on the final draft of this thesis. ii Table of contents Table of contents Abstract ............................................................................................................................i Acknowledgements............................................................................................................ii Table of contents................................................................................................................iii List of figures .....................................................................................................................xi List of tables ......................................................................................................................xiv Chapter 1 Introduction................................................................................................1 1.1 Background to the problem.............................................................................2 1.2 Objectives of the work....................................................................................4 1.3 Approach of the work.....................................................................................4 1.4 Novel characteristics of the work ....................................................................7 1.5 Contributions to the research area ...................................................................7 1.6 Structure of the thesis......................................................................................8 Chapter 2 Time and Interactivity................................................................................11 2.1 Background....................................................................................................12 2.1.1 The Human memory........................................................................12 2.1.1.1 Working memory............................................................12 2.1.1.2 Long-term memory.........................................................13 2.1.1.3 Effect of interruptions ......................................................13 2.1.2 Cognitive models ............................................................................13 2.1.2.1 GOMS Model................................................................13 2.1.2.2 Keystroke-Level Model..................................................14 2.2 Time and the interactive process......................................................................15 2.2.1 Response time ................................................................................15 2.2.2 Impact of delays .............................................................................17 2.2.3 Need for feedback..........................................................................18 2.2.4 Types of feedback..........................................................................19 2.2.4.1 Alert box........................................................................19 2.2.4.2 Progress Indicator...........................................................19 2.2.5 Coping strategies ............................................................................19 2.3 Interaction over the Web.................................................................................20 2.3.1 Problem areas.................................................................................21 2.3.1.1 Response time.................................................................21 iii Table of contents 2.3.1.2 Network latency.............................................................21 2.3.1.3 Collaborative interaction..................................................21 2.3.2 Coping Strategies............................................................................22 2.3.3 Potential solutions ...........................................................................23 2.4 Temporal properties of interactive systems.......................................................23 2.4.1 Interface behaviour .........................................................................23 2.4.1.1 Events, status and agents.................................................23 2.4.1.2 Mediating status ..............................................................24 2.4.2 Pace of Interaction..........................................................................24 2.4.2.1 Pace of communication channel.......................................25 2.4.2.2 Pace of task....................................................................25 2.4.2.3 Pace of users ..................................................................25 2.4.2.4 Delays ............................................................................26 2.4.2.5 Coping with delays..........................................................26 2.4.2.6 Time granularity...............................................................27 2.5 Summary........................................................................................................28 Chapter 3 Single-user Interface and Architecture Issues.........................................30 3.1 Requirements..................................................................................................30 3.1.1 Separation......................................................................................31 3.1.2 Direct manipulation.........................................................................31 3.1.3 Feedback.......................................................................................31 3.1.4 Consistency....................................................................................32 3.2 Architectural models .......................................................................................32 3.2.1 Seeheim model...............................................................................32 3.2.2 Arch/Slinky model..........................................................................33 3.2.3 Model-View-Controller..................................................................34 3.2.4 Presentation-Abstraction-Control....................................................36 3.3 Analysing architectural models.........................................................................37 3.3.1 Conceptual architecture...................................................................37 3.3.2 Physical architecture........................................................................38 3.4 Interface development tools.............................................................................39