CS 502: Computing Methods for Digital Libraries

1
CS 502 Computing Methods for Digital Libraries

• Lecture 21
• Usability and user-interfaces

2
Administration
3
Usability
Usability of a computer system is a combination
of factors User interface design
Functionality Performance Help systems
and documentation Freedom from errors
4
Levels of usability
interface design functional design data and
metadata computer systems and networks
conceptual model
5
Conceptual model
The conceptual model is the user's internal model
of what the system provides The desk top
metaphor -- files and folders The web model
-- click on hyperlinks Library
models search and retrieve search, browse and
retrieve
6
(No Transcript)
7
(No Transcript)
8
Hierarchical browsing
Level 0
Level 1
Level 2
9
(No Transcript)
10
Interface design
The interface design is the appearance on the
screen and the actual manipulation by the user
Fonts, colors, logos, key board controls,
menus, buttons Mouse control or keyboard
control? Conventions (e.g., "back",
"help") Example Screen space utilization in
American Memory page turner.
11
Principles of interface design
Interface design is partly an art there are
general principles Consistency -- in
appearance, controls, and function.
Feedback -- what is the computer system is
doing? why does the user see
certain results? Users should be able to
interrupt or reverse actions Error
handling should be simple and easy to comprehend
Skilled users offered shortcuts
beginners have simple, well-defined options
The user should feel in control
12
Functional design
The functional design, determines the functions
that are offered to the user Selection of
parts of a digital object Searching a list
or sorting the results Help information
Manipulation of objects on a screen Pan or
zoom
13
(No Transcript)
14
(No Transcript)
15
Same functions, different interface
Example the desk top metaphor Mouse -- 1
button (Macintosh), 2 button (Windows)
or 3 button (Unix) Close button -- left of
window (Macintosh) right of
window (Windows)
16
Data and metadata
Structural data and metadata stored by the
computer system enable the functions and the
interface The desktop metaphor has the
concept of associating a file with an
application. This requires a file type to be
stored with each file -- extension to filename
(Windows and Unix) -- resource fork (Macintosh)
17
Computer systems and networks
The performance, reliability and predictability
of computer systems and networks is crucial to
usability Response time instantaneous for
mouse tracking and echo of key stroke 5 seconds
for simple transactions Example Pipelined
algorithm for the Mercury page turner
Quality of Service for real time information
18
Design tensions in networked systems
Client computers and network connections
vary greatly in capacity Client software may
run on various operating systems it may be
current or an earlier version System
designers wish to control clients users wish to
configure their own environments
19
Varieties of user interfaces

• End user interface. Allows a library user to
  search, browse, or retrieve known items. Uses
  structural metadata to present the collections to
  the user.
• Librarian and system administrator interface.
  Provides services for an authenticated user to
  view, add, delete, or edit digital objects.
• Batch interface. Provides a method to load large
  numbers of digital objects automatically.
• Structure editor. Allows user to review and edit
  the structure of a collection.

20
Disabilities
What if the user is visually impaired or
color blind? does not speak English? is a poor
typist? There is a tradition of blind
programmers Navigation of web sites need not
be only visual
21
Evaluation of usability
Observing users (user protocols) Focus
groups Measurements effectiveness in
carrying out tasks speed Expert review
Competitive analysis
22
Usability and cost
Performance may be expensive in hardware or
special software development User interface
development may be a major part of a software
development project Costs are multiplied if
a user interface has to be used on different
computers or migrate to different versions of
systems Web browsers provide a general purpose
user interface that others maintain