introduction to interactive systems

Jan-14-05 © 1997-2005 by David A. Carr 1 L

INSTITUTIONEN FÖRSYSTEMTEKNIK

LULEÅ TEKNISKA UNIVERSITET

Introduction to Interactive Systems

SMD158

Interactive Systems

Spring 2005


Overview

• What is an interactive system?

• Software lifecycle

• Layers of an interactive system

• Interactive systems design




What Is an Interactive System?


What is an Interactive System?

• Any system that accepts input from the user andprovides information as output to the user.

• Note,we will concentrate on window-based systems,but the vast majority of interactive systems are notwindow-based.

• Examples:- Microwave ovens - Mobil telephones

- Pocket calculators - Airliners


Two Points-of-View

• Interactive systems can be viewed from:- The user perspective,

- The system perspective

• This course will concentrate on the system point-of-view.

• However, the user point-of-view is still important.


Two Points-of-View

• To the user the system is:- A tool for accomplishing tasks

- Something that receives input

- And hopefully, displays output

- All too often, a source of frustration

• To the system the user is:- A source of asynchronous input

- An indirect target for output through various devices (display,speaker, lights, ...)


Ignoring the User

• Ignoring the user, can have serious consequences

• Examples:- The Pollack’s election documents and a poorly designed text

editor

- The Vincennes




Software Life Cycle


The Software Engineering Life Cycle

• Six phases:- Requirements definition

- Specification

- Implementation

- Testing

- Installation

- Maintenance

• Always presented as a linear progression, but in realitythings are not so.


Requirements Definition

• Semi-formal description of the system• Specifies the properties and services that the system must

perform- Usually prioritized

• Often specifies the execution environment• Usually provided by the customer, but:

- The customer is not always the user- The customer does not always know exactly what is wanted- It usually changes during the development cycle

• The designer must resolve incomplete and/or conflictingrequirements


Specification

• Two phases, functional and internal

• Functional phase- Describes the functions that the system will have

- Divides them between the operator and the system

• Internal phase- Maps the functions to software

- Relates the functions to specific software components

- Defines: data structures, modules, algorithms, ...


Implementation & Testing

• Overlap

• Implementation- Development of components

- Integration (Very time consuming if the internal design is notdone well.)

• Testing- Module testing

- Systems testing

- Acceptance testing


Installation & Maintenance

• Students always escape these, but maintenance istypically more than half of the effort.

• Installation usually proceeds acceptance testing.

• Installation is time consuming and usually requiressignificant user support.

• Maintenance is usually the largest part of any system’slife.

• Revision follows the same SE model, although it ismaintenance.


The Spiral Model


Software Engineering and the User Interface

• Iterative design of the user interface tends to blendspecification, implementation, and testing.

• User involvement can result in changes to therequirements after they are “complete”.

• Failure to test early with real users can result in:- System failure

- An immediate demand for a new version




Layers of an Interactive System


An Interactive Systems View of the Software

Functional Core Dialog Control

Interaction Objects Window System

Device Drivers

We concentrate

here


Functional Core

• A.k.a., the application, the backend

• Implements domain knowledge (e.g. IOGs)

• Logically separated from all user interface objects- Independent of input and output types (pen vs. keyboard, or

display vs. audio)

- But, still aware that there is a user


Dialog Control

• Controls sequencing

• Function availability at a specific time

• Interaction style (e.g., menu vs. command line)


Interaction Objects

• A.k.a. widgets, interactors

• Logical devices which the user manipulates with theinput devices

• Includes:- Presentation (output)

- Interaction (input)

- Miniature dialog (sequencing)


Window System & Device Drivers

• Window System- Interface between the interactors and the device drivers.

- Provides a logical device that hides machine dependentdetails.

- Provides for sharing of physical devices (e.g., mouse &display).

• Device Drivers- Map from an abstract device to a physical.

- Direct interface to the hardware.


This Is Only One Model

• Note, not everyone agrees that the functional core can beseparated from the interface.- Interaction often needs data that is in the functional core.

+ Runtime generated lists

+ Status of real-time equipment that is being monitored

+ User input while running IOGs in debug mode.

- Separation can lead to time lags between actions and events

+ E.g., mouse events winding up in the wrong window




Interactive Systems Design


The Design Phases

• Remember the six phases of the software engineeringlife cycle :- Requirements definition

- Specification

- Implementation

- Testing

- Installation

- Maintenance

• Design encompasses the first two.


Another View of the Process

• Define the problem

• Model the operator

• Perform a task analysis

• Define computer objects and functions

• Design the appearance and behavior of the userinterface

• Evaluate the design


View Overlap

• Define the problem

• Model the operator

• Perform a task analysis

• Define objects and functions

• Design the user interface

• Evaluate

RequirementsAnalysis

FunctionalDesignInternal

Design

All


Define the Problem

• Begin with a one-sentence problem-statement.- This system will allow a systems developer to design widgets

using Interaction Object Graphs and edit the graphs on aworkstation.

• The statement should include four elements:- Performers of the activity, a.k.a. the users (system

developers)- Supported activity (widget design)- Form of solution (any workstation on the Internet)- Level of support (edit)

• Next, expand the four elements.


The Performers of the Activity

• Who are they?

• What is their training?

• Why are they going to use the new system?

• How are they doing things now?

• What general needs do they have?

• What specific needs do they have?


Usability Criteria

• Speed of performance

• Incidence of errors

• Recoverability from errors

• Speed of learning to use the system

• Retention of operation skill

• Flexibility of the system with respect to the users way of working

• Ease with which users can reorganize activities supported by thesystem

• User Satisfaction


Specific Needs

• Support for:- Logical correctness

- Readability

- Storage and retrieval

- Interface to other software

• Solutions?


Supported Activity

• What type of widget?- Needs further refinement

- State based?, continuous

• What level of editing?- Diagram itself

- Logical function

- Widget appearance?

• Interfaces to which systems?


Form of Solution

• Workstation- Java capable (applet or application?)

- Other requirements?

• Target environment?- Workstation itself

- Embedded devices


Level of Support

• Easy isn’t very descriptive.

• Better parameters- Accuracy

- Time to accomplish a task

- Few errors

- Quick discovery and recovery from errors

- Satisfaction

- Flexibility with different instruments

- Flexibility with different tasks


Model the Operators

• Remember the questions- Who are they?

- What is their training?

- Why are they going to use the new system?

- How are they doing things now?

- What general needs do they have?

- What specific needs do they have?

• How do we answer them?- Interviews

- Questionnaires

- Observation in the workplace


Perform a Task Analysis

• State broad tasks and decompose them

• Analyze the decomposition- Semantic inconsistencies

- Parallel tasks

- Identify special tasks

+ Frequent

+ Common

+ Complex

• Partition tasks between users and the system


Broad Tasks for the IOG Editor

• Operator Goals- Add and define states

- Connect states with arcs, define arcs

- Test IOG execution

- Save work

- Browse IOG

- Test IOG

- Create widget


Decomposition Add and Define States

• Select state type

• Place on work surface

• Insert state specific data- Name

- States for meta states

- Pictures for display states

- Annotations in standard states


Define Objects and Functions

• Make semantic objects in the functional corecorrespond to task objects- Each widget, state, arc, ...

• Implement syntax in the UI to facilitate taskaccomplishment- Multiple views

- Status indicators

• Define commands based on task decomposition


Define Objects and Functions

• Provide general services- Macros

- Undo/redo

- Cut/copy/paste

- On-line help

- Defaults

• Determine who controls the interaction- User or system

- Stress collaboration


Design the UI Details

• Interaction objects should map syntax to semantics

• Keep appearance and behavior consistent- Choose an appropriate metaphor

- Use a UI toolkit (Swing/Jazz)

• Use forms and menus- Specify actions

- Display units on forms

- Chose good defaults and display them


Design the UI Details

• Support semantic distance (making things distinct and separate)by using- prefix or postfix syntax

- precise and consistent naming

- consistent spatial layout

• Provide informative feedback- Show the interaction objects useful in a task context

- Indicate forbidden actions

- Display the current system mode (NO HIDDEN MODES!)

- Inform the operator of long response times

- Map movements of pointers on the screen


Evaluation

• Simulations

• Mock-ups

• Scenarios

• Test with a representative operator


Questions?

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