Post on 19-Dec-2015
transcript
SOFT3057 - Interactive Systems
User Centered Design Process
Knowledge of the user as an information processor as part of an occupational
group
Knowledge of theuser’s job and it’scomponent tasks
Knowledge of the user’swork environment- organisational- physical
Knowledge of design principles- dialogue design-information presentation-graphics design
Knowledge of systems- delivery platform- I/O devices
(knowledge of how to )Produce a initial design andbuild a prototype
(knowledge of how to)evaluate and test prototype
Requirements specification-usability specification
SOFT3057 - Interactive Systems
System Related User Characteristics
What characteristics can you expect of the users of your interface? frequency of use discretion to use the system knowledge of the task which the system will support knowledge of computers experience of other similar systems general abilities, e.g. literacy, vision attitude towards computers (and your system) existing skills (keyboard, mouse)
SOFT3057 - Interactive Systems
Three-Dimensional Framework
Three Dimensional Framework for User Classification
Kno
wle
dge
of C
ompu
ters
Knowledge of Task
Frequency of Use
(low) (high)
(high)
(high)
SOFT3057 - Interactive Systems
Design implications
Provide for high degree of sophistication in interface: range of functions provided, flexibility to combine functions to provide new commands, possibilities to customise interface to own needs.
Lower requirement for user support than with other user types.
Can utilise programming languages and extensible command languages (e.g. macros and scripts).
Computer professionals
SOFT3057 - Interactive Systems
Highly variable group in terms of knowledge and
experience
Design implications Important to support the user ‘guessing’ or experimenting
with how operations can be carried out at the interface. Consistency and a close match to the user’s task model is important.
Frequency of use determines how much the user can be expected to learn short cuts and accelerators.
User support provided by the interface is important.
Professionals without programming experience
SOFT3057 - Interactive Systems
Design implications Can anticipate significant learning of routine operations to
take place, so can make use of abbreviations and codes for data input.
Can expect strong user skills to be developed, such as keyboard skills.
Error messages must be clear and provide specific guidance for recovery.
Cannot expect users to develop deeper knowledge or understanding of the computer system without specific training.
Skilled clerks
SOFT3057 - Interactive Systems
Design implications Every type of user error must be trapped. This type of
user will not be able to infer what is happening or the cause of an error condition.
Require explicit on-screen prompts for each step of the dialogue.
High degree of user support and a low degree of sophistication is required in the interface. ?
Naïve users
SOFT3057 - Interactive Systems
Task Analysis
provides an essential basis for early stages of interface design evaluation of design at early and late stages structuring training in system use structuring and design of documentation
SOFT3057 - Interactive Systems
Levels of Task Analysis
relate to existing situation or new system.
General Analysis of User Characteristics
Detailed Analysis of tasks in present job(s)
Subset of tasks to be included in new system
Analysis of Actions and Objects in new system
SOFT3057 - Interactive Systems
General Analysis level
who are the users classify the users into one or more groups define characteristics of the group
what are the main task components of the users present job what proportion of time is spent in different tasks what causes variations in this
where are the tasks carried out what equipment (other than the computer system)
are used what communication is there between the user and
other people
SOFT3057 - Interactive Systems
Detailed analysis of tasks in present job
what is the hierarchical structure of main tasks, and subtasks within these main tasks
how do users see the structure of their job in terms of tasks for each task identified
what information is required what actions arise or result from decisions what feedback is provided on effect of actions what affects successful performance what are the possible errors and what factors cause these
SOFT3057 - Interactive Systems
Detailed analysis of tasks in present job
what are the good features of the existing system which should be retained in the subsequent redesign
what are the bad features of the existing system that should be designed out
what skills are required for each task how are the required skills trained initially and how are
these retained
SOFT3057 - Interactive Systems
Actions and Objects
Low level (down the hierarchy) task descriptions can be formulated as actions performed on task-related objects e.g... change start time of appointment object: appointment attribute: start time action: change/edit
a dictionary of objects, attributes and associated actions can be constructed through process of rationalisation generification
SOFT3057 - Interactive Systems
Building an object dictionary
interviews with users provide textual descriptions of tasks these can be analysed by identifying
nouns (candidate objects) verbs (candidate actions)
process of generification to identify what are essentially descriptions of the same thing
process of hierarchy building to identify objects as members of related classes
SOFT3057 - Interactive Systems
Objectives of task analysis to support interface design
identify a hierarchy of user goals, tasks and subtasks together with a plan describing how and when these are done
represent lowest level task as a set of procedures (using something like pseudocode) include statements of information requirements and exception
conditions identify set of actions and associated objects
SOFT3057 - Interactive Systems
Hierarchical task analysis (HTA)
Originally devised to define training requirements in process industry - method needs additionally descriptions of information requirements for lowest level sub-
operations dictionary of objects and associated actions
Representation tree diagram or tabular format
Advantages of HTA simple, informal notation but still requires considerable skills on part of analyst.
SOFT3057 - Interactive Systems
Example of HTADelete block of text in a word processor
1.Deleteblock of text Goal
SOFT3057 - Interactive Systems
Example of HTADelete block of text in a word processor
1.Deleteblock of text Goal
2) Select 'cut' from Edit menu
1) Select block of text
or 2) Select cut icon from toolbar
or 2) Press 'delete' key
then
Tasks
SOFT3057 - Interactive Systems
HTA representation
1.Deleteblock of text
1. Selecttext block
2. Press‘delete’
3. Select cutfrom edit menu
4. Select cut iconfrom toolbar
SOFT3057 - Interactive Systems
HTA representation
1.Deleteblock of text
1. Selecttext block
2. Press‘delete’
3. Select cutfrom edit menu
4. Select cut iconfrom toolbar
Plan 1: 1-2 or 1-3 or 1-4
SOFT3057 - Interactive Systems
HTA representation
1.Deleteblock of text
1. Selecttext block
2. Press‘delete’
3. Select cutfrom edit menu
4. Select cut iconfrom toolbar
Plan 1: 1-2 or 1-3 or 1-4
1) Anchor the start of the block2) adjust the extent of the block
3) Anchor end of the block
then
then
Subtasks
SOFT3057 - Interactive Systems
HTA representation of tasks and subtasks
1.Deleteblock of text
1. Selecttext block
2. Press‘delete’
3. Select cutfrom edit menu
4. Select cut iconfrom toolbar
1.Define start of textselection
2. Adjust lengthof text selection
3. Define end oftext selection
Plan 1: 1-2 or 1-3 or 1-4
Plan: 1.2 1-2-3
SOFT3057 - Interactive Systems
HTA representation of tasks and subtasks
1.Deleteblock of text
1. Selecttext block
2. Press‘delete’
3. Select cutfrom edit menu
4. Select cut iconfrom toolbar
1.Define start of textselection
2. Adjust lengthof text selection
3. Define end oftext selection
Plan 1: 1-2 or 1-3 or 1-4
Plan: 1.2 1-2-3
Procedure
1) position text insertion in front of first character of block2) ...
SOFT3057 - Interactive Systems
How far to decompose tasks?
1.Deleteblock of text
1. Selecttext block
2. Press‘delete’
3. Select cutfrom edit menu
4. Select cut iconfrom toolbar
1.Define start of textselection
2. Adjust lengthof text selection
3. Define end oftext selection
Plan 1: 1-2 or 1-3 or 1-4
Plan: 1.2 1-2-3
SOFT3057 - Interactive Systems
How far to decompose tasks?
1.Deleteblock of text
1. Selecttext block
2. Press‘delete’
3. Select cutfrom edit menu
4. Select cut iconfrom toolbar
1.Define start of textselection
2. Adjust lengthof text selection
3. Define end oftext selection
Plan 1: 1-2 or 1-3 or 1-4
Plan: 1.2 1-2-3
.. as far as is useful for the analysis