1. Week: 05 Human-Computer Interaction
Waseem Iqbal
Assistant Professor
PhD-Scholar (Adaptive Interface for Mobile Devices in User’s Context)

2. Acknowlwdgement
Dr. Ibrar Hussain (Assistant Professor / HEC Approved Supervisor)
PhD. in Computer Science
Pervasive Computing Research Lab, Zhejiang University, China.
Carried out 6 months collaborative research work with HCI & SE group at University of Colorado, Boulder, USA.
Human Computer Interaction (Book)
3rd Edition by Alan Dix

3. Assignment No:1
Design a TV remote for patients in the hospital ? Discuss what will be main objectives while designing such devices for patients in the hospital ?
Submission deadline: 18/03/2017
After due date, assignment will not be accepted
Clearly mention your Section and Roll no. on the Assignment

4. processing and networks
finite speed
limits of interaction
networked computing

5. Finite processing speed
Designers tend to assume fast processors, and make interfaces more and more complicated
But problems occur, because processing cannot keep up with all the tasks it needs to do
cursor overshooting because system has buffered keypresses
icon wars - user clicks on icon, nothing happens, clicks on another, then system responds and windows fly everywhere
Also problems if system is too fast - e.g. help screens may scroll through text much too rapidly to be read

6. Moore’s law computers get faster and faster! 1965 …
Gordon Moore, co-founder of Intel, noticed a pattern
processor speed doubles every 18 months
PC … 1987: 1.5 Mhz, 2002: 1.5 GHz
similar pattern for memory
but doubles every 12 months!!
hard disk … 1991: 20Mbyte : 2002: 30 Gbyte
baby born today
record all sound and vision
by 70 all life’s memories stored in a grain of dust!
/e3/online/moores-law/

7. The myth of the infinitely fast machine
Implicit/understood/hidden assumption … no delays an infinitely fast machine
what is good design for real machines?
good example … the telephone :
type keys too fast
hear tones as numbers sent down the line
actually an accident of implementation
emulate in deisgn

8. Limitations on interactive performance
Computation bound
Computation takes ages, causing frustration for the user
Storage channel bound
Bottleneck in transference of data from disk to memory
Graphics bound
Common bottleneck: updating displays requires a lot of effort - sometimes helped by adding a graphics co- processor optimised to take on the burden
Network capacity
Many computers networked - shared resources and files, access to printers etc. - but interactive performance can be reduced by slow network speed

9. Networked computing Networks allow access to …
large memory and processing
other people (groupware, )
shared resources – esp. the web
Issues
network delays – slow feedback
conflicts - many people update data
unpredictability

10. The internet history … 1969: DARPANET US DoD, 4 sites
1971: 23; 1984: 1000; 1989: 10000
common language (protocols):
TCP – Transmission Control protocol
lower level, packets (like letters) between machines
IP – Internet Protocol
reliable channel (like phone call) between programs on machines
, HTTP, all build on top of these

11. the interaction

12. The Interaction
Interaction models help us to understand what is going on in the interaction between user and system. They address the translations between what the user wants and what the system does.
Ergonomics looks at the physical characteristics of the interaction and how these influence its effectiveness.

13. The Interaction (Cont.)
The dialog between user and system is influenced by the style of the interface (the nature of user/system dialog).
The interaction takes place within a social and organizational context that affects both user and system.

14. What is interaction?
Communication
user  system

15. terms of interaction Norman model interaction framework
Models of Interaction
terms of interaction
Norman model
interaction framework

16. Terms of Interaction
A domain defines an area of expertise and knowledge in some real-world activity. e.g. graphic design.
Tasks are operations to manipulate the concepts of a domain. e.g. … select fill tool, click over triangle.
A goal is the desired output from a performed task. e.g. create a solid red triangle.
An intention is a specific action required to meet the goal.

17. Terms of Interaction (cont.)
Task analysis involves the identification of the problem space for the user of an interactive system in terms of the domain, goals, intentions and tasks.
The concepts used in the design of the system and the description of the user are separate, and so we can refer to them as distinct components, called the System and the User, respectively.

18. Terms of Interaction (cont.)
The System and User are each described by means of a language that can express concepts relevant in the domain of the application.
The core language describes computational attributes of the domain relevant to the System state.
The task language describes psychological attributes of the domain relevant to the User state.

19. The execution-evaluation cycle (Donald Norman’s model)
The interactive cycle can be divided into two major phases: execution and evaluation, and this can be subdivided in seven stages:
user establishes the goal
formulates intention
specifies actions at interface
executes action
perceives system state
interprets system state
evaluates system state with respect to goal
Norman’s model concentrates on user’s view of the interface

20. execution/evaluation loop
system
evaluation
execution
goal
user establishes the goal
formulates intention
specifies actions at interface
executes action
perceives system state
interprets system state
evaluates system state with respect to goal

21. execution/evaluation loop
system
evaluation
execution
goal
user establishes the goal
formulates intention
specifies actions at interface
executes action
perceives system state
interprets system state
evaluates system state with respect to goal

22. execution/evaluation loop
system
evaluation
execution
goal
user establishes the goal
formulates intention
specifies actions at interface
executes action
perceives system state
interprets system state
evaluates system state with respect to goal

23. execution/evaluation loop
system
evaluation
execution
goal
user establishes the goal
formulates intention
specifies actions at interface
executes action
perceives system state
interprets system state
evaluates system state with respect to goal

24. Using Norman’s model
The gulf of execution is the difference between the user’s formulation of the actions to reach the goal and the actions allowed by the system.
If the actions allowed by the system correspond to those intended by the user, the interaction will be effective.
The interface should therefore aim to reduce this gulf.

25. The gulf of evaluation is the distance between the physical presentation of the system state and the expectation of the user.
If the user can readily evaluate the presentation in terms of his goal, the gulf of evaluation is small.
The more effort that is required on the part of the user to interpret the presentation, the less effective the interaction.
Gulf of Evaluation
user’s expectation of changed system state ≠ actual presentation of this state

26. Human Error – Slips and Mistakes
Human errors are often classified into slips and mistakes.
If you understand a system well you may know exactly what to do to satisfy your goals – you have formulated the correct action.
However, perhaps you mistype or you accidentally press the mouse button at the wrong time. These are called slips; you have formulated the right action, but fail to execute that action correctly.

27. If you don’t know the system well you may not even formulate the right goal. E.g., you may think that the magnifying glass icon is the ‘find’ function, but in fact it is to magnify the text. This is called a mistake.
Slips may be corrected by, for instance, better screen design, perhaps putting more space between buttons.
Mistakes need users to have a better understanding of the systems, so will require far more radical redesign or improved training, perhaps a totally different metaphor/combinations/symbol for use.

28. Abowd and Beale framework
extension of Norman…
their interaction framework has 4 parts
user
input
system
output
each has its own unique language interaction  translation between languages
problems in interaction = problems in translation

29. Using Abowd & Beale’s model
User intentions  translated into actions at the interface  translated into alterations of system state  reflected in the output display  interpreted by the user
General framework for understanding interaction
not restricted to electronic computer systems
identifies all major components involved in interaction
allows comparative assessment of systems
an abstraction

30. A Framework for HCI