Implementation Support: Introduction Elements of windowing systems Programming the application User interface management systems 4.2 Evaluation Techniques What is evaluation? Goals of evaluation Choosing an evaluation method

1. Chapter 4
Implementation Support and Evaluation
Techniques
1
Human Computer Interaction
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

2. 26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia
2
 Implementation Support
 Elements of windowing systems
 Programming the application
 User interface management systems
 Evaluation Techniques
 What is evaluation?
 Goals of evaluation
 Choosing an evaluation method

3. Implementation Support
3
 The detailed design specification gives the programmer instructions
( what the interactive application must do)
 The programmer must translate that into machine executable
instructions ( how that will be achieved on the available
hardware devices).
(Ie. the level of the software that runs the hardware devices )
 This software provides the ability to do things like read events from
various input devices and write primitive graphics commands to a
display.
 The job is very tedious and highly error prone .
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

4. Windowing Systems
4
 are core support for separate and simultaneous user system activity
Elements of Windowing Systems
 some visual display screen, a keyboard and some pointing device, such as a
mouse
 A given windowing system will have a fixed generic language for the
abstract terminal (called its imaging model) to describe very arbitrary
images and then can be translated to the language of many other specific
devices (ie device driver) and then any application program can access it.
Example for image models for output and (partially) input
− pixels:-rows and columns of points –on or off , color
− Graphical Kernel System (GKS):- Collection of segment model the
screen ,each segment indicates commands
− Programmers' Hierarchical Interface to Graphics (PHIGS):-
collection of editable segments model the screen.
− PostScript:-language was developed by Adobe Corporation which
models the screen as a collection of paths which serve as infinitely thin
boundaries or stencils which can be filled in with various colors or
textured patterns and images.
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

5. Windowing systems Con…
5
The other feature of windowing systems is resource
sharing:
− achieving simultaneous user tasks.
− supports independent processes
− isolation of individual applications
The role of a windowing system
 management of multiple, independent but simultaneously
active applications.
 independence from the specifics of programming separate
hardware devices;
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

6. The role of a windowing system
6 26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

7. Programming the Application
7
 Two programming paradigms- used to organize the flow of control
within the application.
1. read–evaluation loop
2. notification based
 The windowing system does not necessarily determine which of
these two paradigms is to be followed.
Read-Evaluation loop
 Programming on the Macintosh follows this paradigm.
 The server sends user inputs as structured events to the client
application.
 The client application is programmed to read any event passed to it
and determine all of the application-specific behavior that results
as a response to it.
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

8. Programming the Application
con…
8
Read-Evaluation loop Programming Paradigm: Logical flow and
pseudo-code for Client application
repeat
read-event(myevent)
case myevent.type
type_1:
do type_1 processing
type_2:
do type_2 processing
...
type_n:
do type_n processing
end case
end repeat
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

9. Programming the Application
con…
9
Notification based programming paradigm
 In which the main control loop for the event processing
does not reside within the application.
 The application program informs the notifier what events
are of interest to it, and for each event declares one of
its own procedures as a callback before turning control
over to the notifier.
 When the notifier receives an event from the window
system,
 it sees if that event was identified by the application
program and, if so, passes the event and control over to the
callback procedure that was registered for the event.
 After processing, the callback procedure returns control to
the notifier, either telling it to continue receiving events or
requesting termination
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

10. Programming the Application
con…
10
Notification based programming
paradigm
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

11. User Interface Management Systems
11
 The term UIMS is used quite widely in both industrial and academic circles
and has come to represent a variety of topics.
The main concerns of a UIMS, for our purposes, are:
 a conceptual architecture for the structure of an interactive system which
concentrates on a separation between application semantics and presentation
 support techniques for implementing a separated application and
presentation whilst preserving the intended connection between them
 support techniques for managing, implementing and evaluating a run-time
interactive environment.
There are many good arguments to support this separation of concerns:
 Portability to allow the same application to be used on different systems.
 Reusability -components can be reused in order to cut development costs.
 Multiple interfaces To enhance the interactive flexibility of an application,
several different interfaces can be developed.
 Customization The user interface can be customized by both the designer and
the user to increase its effectiveness without having to alter the underlying
application
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

12. Systems
Con…
12
The logical components of a UIMS
 Presentation The component responsible for the appearance of
the interface, including what output and input is available to the
user.
 Dialog control The component which regulates the
communication between the presentation and the application.
 Application interface The view of the application semantics that
is provided as the interface.
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

13. Evaluation Techniques
13
What is Evaluation?
 tests usability and functionality of system
 occurs in laboratory, field and/or in collaboration with users
 evaluates both design and implementation
 should be considered at all stages in the design life cycle
Goals of Evaluation
 to assess the extent and accessibility of the system’s
functionality,
 to assess users’ experience of the interaction,
 to identify any specific problems with the system
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

14. Evaluation Techniques con…
14
Choosing an Evaluation Method
how do we decide which methods are most appropriate for our needs?
Each method has its particular strengths and weaknesses and each is useful if
applied appropriately. However, there are a number of factors that should be
taken into account when selecting evaluation techniques.
The choice of evaluation method is largely dependent on what is required of
the evaluation
when in process: design vs. implementation
style of evaluation: laboratory vs. field
how objective: subjective vs. objective
type of measures: qualitative vs. quantitative
level of information: high level vs. low level
level of interference: obtrusive vs. unobtrusive
resources available: time, subjects,
equipment, expertise
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia

15. Evaluation Techniques con…
15
 Evaluation methods vary in the stage at which they are commonly
used and where they can be used. Some are more subjective than
others and provide qualitative rather than quantitative measures.
Some provide immediate information while others get feedback after
the event. However, the more immediate methods also tend to
intrude (interrupt) most seriously on the interaction. Finally, some
require more resources in terms of time, equipment and expertise
than others.
26 May 2016
Presented by Dr. J. VijiPriya,
Assistant Professor, Hawassa University,
Ethiopia