Sri Vidya College of Engineering & Technology Lecture Notes ( unit 3)

Unit 3

Cognitive models

• goal and task hierarchies

• linguistic

• physical and device

• architectural

They model aspects of user:

• understanding , knowledge, intentions, processing

Common categorisation:

• Competence vs. Performance

• Computational flavour, No clear divide

Goal and task hierarchies

• Mental processing as divide-and-conquer

• Example: sales report

produce report

gather data

. find book names

. . do keywords search of names database

. . . … further sub-goals

. . sift through names and abstracts by hand

. . . … further sub-goals

. search sales database - further sub-goals

layout tables and histograms - further sub-goals

write description - further sub-goals

Issues for goal hierarchies

• Granularity

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– Where do we start?

– Where do we stop?

• Routine learned behaviour, not problem solving

– The unit task

• Conflict

– More than one way to achieve a goal

Error

Techniques

• Goals, Operators, Methods and Selection (GOMS)

• Cognitive Complexity Theory (CCT)

• Hierarchical Task Analysis (HTA)

GOMS

Goals - what the user wants to achieve

Operators - basic actions user performs

Methods - decomposition of a goal into subgoals/operators

Selection -means of choosing between competing methods

Example:

GOAL: CLOSE-WINDOW

. [select GOAL: USE-MENU-METHOD

. MOVE-MOUSE-TO-FILE-MENU

. PULL-DOWN-FILE-MENU

. CLICK-OVER-CLOSE-OPTION

GOAL: USE-CTRL-W-METHOD

. PRESS-CONTROL-W-KEYS]

For a particular user:

Rule 1: Select USE-MENU-METHOD unless another

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rule applies

Rule 2: If the application is GAME,

select CTRL-W-METHOD

Cognitive Complexity Theory

• Two parallel descriptions:

– User production rules

– Device generalised transition networks

• Production rules are of the form:

– if condition then action

Transition networks covered under dialogue models

Example: editing with vi

• Production rules are in long-term memory

• Model working memory as attribute-value mapping:

(GOAL perform unit task)

(TEXT task is insert space)

(TEXT task is at 5 23)

(CURSOR 8 7)

• Rules are pattern-matched to working memory,

e.g., LOOK-TEXT task is at %LINE %COLUMN

is true, with LINE = 5 COLUMN = 23.

Linguistic notations

• Understanding the user's behaviour and cognitive difficulty based on analysis of language
between user and system.

• Similar in emphasis to dialogue models

• Backus–Naur Form (BNF)

Task–Action Grammar (TAG)

• Backus-Naur Form (BNF) Very common notation from computer science

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• A purely syntactic view of the dialogue

• Terminals

– lowest level of user behaviour

– e.g. CLICK-MOUSE, MOVE-MOUSE

• Nonterminals

– ordering of terminals

– higher level of abstraction

e.g. select-menu, position-mouse

BNF Example:

• Basic syntax:

– nonterminal ::= expression

• An expression

– contains terminals and nonterminals

– combined in sequence (+) or as alternatives (|)

draw line ::= select line + choose points + last point

select line ::= pos mouse + CLICK MOUSE

choose points ::= choose one | choose one + choose points

choose one ::= pos mouse + CLICK MOUSE

last point ::= pos mouse + DBL CLICK MOUSE

pos mouse ::= NULL | MOVE MOUSE+ pos mouse

Task Action Grammar (TAG)

• Making consistency more explicit

• Encoding user's world knowledge

• Parameterised grammar rules

• Nonterminals are modified to include additional semantic features

Consistency in TAG

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• In BNF, three UNIX commands would be described as:

copy ::= cp + filename + filename | cp + filenames + directory

move ::= mv + filename + filename | mv + filenames + directory

link ::= ln + filename + filename | ln + filenames + directory

• No BNF measure could distinguish between this and a less

consistent grammar in which

link ::= ln + filename + filename | ln + directory + filenames

• consistency of argument order made explicit using a parameter, or semantic feature for file
operations

• Feature Possible values

Op = copy; move; link

• Rules

file-op[Op] ::= command[Op] + filename + filename

| command[Op] + filenames + directory

command[Op = copy] ::= cp

command[Op = move] ::= mv

command[Op = link] ::= ln

Other uses of TAG

• User’s existing knowledge

• Congruence between features and commands

• These are modelled as derived rules

Physical and device models

• The Keystroke Level Model (KLM)

• Buxton's 3-state model

• Based on empirical knowledge of human motor system

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• User's task: acquisition then execution.

– these only address execution Complementary with goal hierarchies

Keystroke Level Model (KLM)

• lowest level of (original) GOMS

• six execution phase operators

– Physical motor: K - keystroking

P - pointing
H - homing
D - drawing

– Mental M - mental preparation

– System R - response

• times are empirically determined.

Texecute = TK + TP + TH + TD + TM + TR

KLM example:

socio-organizational issues and stakeholder requirements

• Organizational issues affect acceptance

– conflict & power, who benefits, encouraging use
• Stakeholders
– identify their requirements in organizational context
• Socio-technical models
– human and technical requirements
• Soft systems methodology
– broader view of human and organizational issues
• Participatory design
– includes the user directly in the design process
• Ethnographic methods
study users in context, unbiased perspective

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Organisational issues
Organisational factors can make or break a system
Studying the work group is not sufficient
– any system is used within a wider context
– and the crucial people need not be direct users
Before installing a new system must understand:
– who benefits
– who puts in effort
– the balance of power in the organisation
– … and how it will be affected
Even when a system is successful
… it may be difficult to measure that success
Organisational structures
• Groupware affects organisational structures
– communication structures reflect line management
– email – cross-organisational communication
Disenfranchises lower management
 disaffected staff and ‘sabotage’
Technology can be used to change management style and power structures
– but need to know that is what we are doing
and more often an accident !
who are the stakeholders?

• system will have many stakeholders with potentially conflicting interests

• stakeholder is anyone effected by success or failure of system

– primary - actually use system

– secondary - receive output or provide input

– tertiary - no direct involvement but effected by success or failure

Facilitating - involved in development or deployment of system

Example: Classifying stakeholders – an airline booking system

An international airline is considering introducing a new booking system for use by associated travel
agents to sell flights directly to the public.

Primary stakeholders: travel agency staff, airline booking staff

Secondary stakeholders: customers, airline management

Tertiary stakeholders: competitors, civil aviation authorities, customers’ travelling companions, airline
shareholders

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Facilitating stakeholders: design team, IT department staff

socio-technical modelling:

• response to technological determinism

• concerned with technical, social, organizational and human aspects of design

• describes impact of specific technology on organization

• information gathering: interviews, observation, focus groups, document analysis

• several approaches e.g.

– CUSTOM

OSTA

CUSTOM

• Six stage process - focus on stakeholders

– describe organizational context, including primary goals, physical characteristics,

political and economic background

– identify and describe stakeholders including personal issues, role in the organization and
job

– identify and describe work-groups whether formally constituted or not

– identify and describe task–object pairs i.e. tasks to be performed and objects used

– identify stakeholder needs: stages 2–4 described in terms of both current and proposed
system - stakeholder needs are identified from the differences between the two

consolidate and check stakeholder requirements against earlier criteria

OSTA

• Eight stage model - focus on task

– primary task identified in terms of users’ goals

– task inputs to system identified

– external environment into which the system will be introduced is described, including
physical, economic and political aspects

– transformation processes within the system are described in terms of actions performed
on or with objects

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– social system is analyzed, considering existing internal and external work-groups and
relationships

– technical system is described in terms of configuration and integration with other systems

– performance satisfaction criteria are established, indicating social and technical

requirements of system

new technical system is specified

soft systems methodology

• no assumption of technological solution - emphasis on understanding situation fully

• developed by Checkland

• seven stages

– recognition of problem and initiation of analysis

– detailed description of problem situation

• rich picture

– generate root definitions of system

• CATWOE

– conceptual model - identifying transformations

– compare real world to conceptual model

– identify necessary changes

determine actions to effect changes

CATWOE

• Clients: those who receive output or benefit from the system

• Actors: those who perform activities within the system

• Transformations: the changes that are affected by the system

• Weltanschauung: (from the German) or World View - how the system is perceived in a
particular root definition

• Owner: those to whom the system belongs, to whom it is answerable and who can authorize
changes to it

Environment: the world in which the system operates and by which it is influenced

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Sri Vidya College of Engineering & Technology Lecture Notes ( unit 3)

Participatory Design

• User is an active member of the design team.

• Characteristics
– context and work oriented rather than system oriented
– collaborative
– iterative
• Methods
– brain-storming
– storyboarding
– workshops
pencil and paper exercises

contextual inquiry:
• Approach developed by Holtzblatt
– in ethnographic tradition but acknowledges and challenges investigator focus
– model of investigator being apprenticed to user to learn about work
– investigation takes place in workplace - detailed interviews, observation, analysis of
communications, physical workplace, artefacts
– number of models created:
• sequence, physical, flow, cultural, artefact
• models consolidated across users
– output indicates task sequences, artefacts and communication channels needed and
physical and cultural constraints
communication and collaboration:
Look at several levels – minutiae to large scale context:
– face-to-face communication
– conversation
– text based communication
– group working

Face-to-face communication

• Most primitive and most subtle form of communication

Often seen as the paradigm for computer mediated communication?

Gestures and body language

• much of our communication is through our bodies

• gesture (and eye gaze) used for deictic reference

head and shoulders video loses this

Back channels

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• Back channels include:

– nods and grimaces

– shrugs of the shoulders

– grunts and raised eyebrows

Utterance begins vague …

… then sharpens up just enough

Restricting media restricts back channels

video – loss of body language

audio – loss of facial expression

half duplex – lose most voice back-channel

responses

text based – nothing left!

Back channels and turn-taking

in a meeting …
– speaker offers the floor
(fraction of a second gap)
– listener requests the floor
(facial expression, small noise)
Grunts, ‘um’s and ‘ah’s, can be used by the:
– listener to claim the floor
– speaker to hold the floor
… but often too quiet for half-duplex channels
e.g. Trans-continental conferences – special problem
lag can exceed the turn taking gap
… leads to a monologue!

Speech act theory

A specific form of conversational analysis

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Utterances characterised by what they do …

… they are acts
e.g. ‘I'm hungry’
– propositional meaning – hunger
– intended effect – ‘get me some food’
Basic conversational act the illocutionary point:
– promises, requests, declarations, …
Speech acts need not be spoken
e.g. silence often interpreted as acceptance …
• Generic patterns of acts can be identified
• Conversation for action (CfA) regarded as central
• Basis for groupware tool Coordinator
– structured email system
– users must fit within CfA structure
not liked by users!

hypertext, multimedia and the world-wide web

Text-imposes strict linear progression on the reader

Hypertext - not just linear

• non-linear structure

– blocks of text (pages)

– links between pages create a mesh or network

users follow their own path through information

Animation

• adding motion to images

– for things that change in time
• digital faces – seconds tick past or warp into the next
• analogue face – hands sweep around the clock face
• live displays: e.g. current system load
– for showing status and progress
• flashing carat at text entry location
• busy cursors (hour-glass, clock, spinning disc)
progress bars
– for education and training
• let students see things happen … as well as being interesting and entertaining
images in their own right
– for data visualisation
• abrupt and smooth changes in multi-dimensional data visualised using animated,
coloured surfaces

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Sri Vidya College of Engineering & Technology Lecture Notes ( unit 3)

• complex molecules and their interactions more easily understood when they are
rotated and viewed on the screen
– for animated characters
wizards and help
video and audio
• now easy to author
– tools to edit sound & video and burn CDs & DVDs
• easy to embed in web pages
– standard formats (QuickTime, MP3)
• still big … but getting manageable
– memory OK … hand held MP3 players, TiVo etc.
– but download time needs care – tell users how big!
• very linear
hard to add ‘links’ often best as small clips or background
application areas
• rapid prototyping
– create live storyboards
– mock-up interaction using links
help and documentation
– allows hierarchical contents, keyword search or browsing
– just in time learning
• what you want when you want it
• (e.g. technical manual for a photocopier)
– technical words linked to their definition in a glossary
links between similar photocopiers
• education
– animation and graphics allow students to see things happen
– sound adds atmosphere and means diagrams can be looked at while hearing explanation
– non-linear structure allows students to explore at their own pace
– e-learning
• letting education out of the classroom!!
e.g. eClass

web technology and issues

web servers and clients
• the web is distributed
– different machines far across the world
– pages stored on servers
– browsers (the clients) ask for pages
sent to and fro across the internet

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Sri Vidya College of Engineering & Technology Lecture Notes ( unit 3)

network issues – timing

• QoS (quality of service)
– bandwidth
• how much information per second
– latency
• how long it takes (delay)
– jitter
• how consistent is the delay
– reliability
• some messages are lost
… need to be resent … increases jitter
– connection set-up
need to ‘handshake’ to start

static web content

TEXT:
• text style
– generic styles universal: serif, sans, fixed, bold, italic
– specific fonts too, but vary between platforms
– cascading style sheets (CSS) for fine control
… but beware older browsers and fixed font sizes
– colour … often abused!
– positioning
– easy .. left, right justified or centred
– precise positioning with DHTML … but beware platforms …
screen size
graphics
• use with care …
– N.B. file size and download time …
this image = 1000 words of text
– affected by size, number of colours, file format
– backgrounds … often add little, hard to read text
– speeding it up

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– caching – reuse same graphics

– progressive formats:
image appears in low res and gets clearer
• formats
– JPEG – for photos
• higher compression but ‘lossy’
• get ‘artefacts’
– GIF for sharp edges
• lossless compression
– PNG supported by current web browsers
• and action
– animated gifs for simple animations
image maps for images you can click on
icons
• on the web just small images
– for bullets, decoration
– or to link to other pages
– lots available!
– design … just like any interface
– need to be understood
– designed as collection to fit …
– under construction
– a sign of the inherent incompleteness of the web
or just plain lazy ??
web colour
• colour palettes
– choose useful 256 colours
– different choices, but Netscape ‘web safe’ 216 are common
each GIF image has its own palette – use for fast download

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