Table of contents
Views on quality
-
users mainly concerned with external
quality (quality in use)
-
Usability
-
Accessibility
-
Transparency
-
Security
-
Safety
-
Interoperability (browsers)
-
…
-
managers and developers mainly
concerned on internal quality
-
Interoperability (platforms)
-
Evolvability
-
Maintainability
-
Portability
-
Cost effectiveness
-
…
But many overlaps
Why?
-
Traditionally scarce attention paid to
quality:
-
ease of writing HTML
-
tolerance by browsers
-
mixed skills development teams
-
many graphical and decorative items
-
universal access design principle often
ignored
-
The evolution:
-
XML based architectures (skill)
-
National regulations are enforcing
accessibility
-
The Italian case: accessibility (minimal
level) and quality (upper levels)
Therefore ...
-
Constraints (by law)
-
Reducing costs
-
Flexibility towards new technologies
Or, again the old problem of maintenance:
-
corrective
-
perfective
-
evolutionary
... and we have yet legacy web sites !!
Some considered evaluation criteria
-
7-Loci (conceptual model to evaluate a generic
web site quality)
-
MiLE (usability-focused evaluation method for
hypermedia applications)
-
Etnoteam (analytic web site quality model) -
see also Polillo: il check-up dei siti Web
(Apogeo)
-
Olsina (very analytical approach)
-
Standardization bodies:
-
W3C (Quality Assurance Initiative) -
technological standards
-
ISO 9126 (Software Engineering - Product
Quality - Part 1: Quality Model - 2000) -
quality of software
-
ISO 9241-11 (Guidance on Usability - 1998)
- usability aspects
-
ISO 13407 (Human centered design processes
for interactive systems - 1999) - user centred
production
-
...
-
MINERVA (cultural web sites)
-
Bremen University (e-government)
Some considerations
-
Mainly qualitative criteria (errors, different
evaluation)
-
Generalised criteria (they have to be weighted
according to site characteristics)
-
Non
orthogonal criteria (same characteristics
accounted more than once)
-
Criteria are essentially accessibility or
usability biased
-
Granularity (page or site)
-
External vs internal quality
-
Need for a metrics and measurable
characteristis
("You cannot control what you cannot measure" --- Tom
De Marco)
A possible strategy
-
Define a quality model
-
Identify possible correlation among
-
external quality (user perception)
-
internal quality (architecture, language,
...)
-
Define a metrics
-
Objective control of usability and
accessibility criteria:
-
automatic analysis
-
an expert evaluates results of an
automatic analysis
-
support in identifying potential quality
issues (es. poor structure, complex navigation,
inconsistent style, etc.)
Five dimensions
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Correctness
-
Presentation
-
Content
-
Navigation
-
Interaction
-
Correctness mainly a technical, internal
aspect
-
Other aspects more related to the user's
perspective
-
Must be checked at page and/or site
granularity, and must be weighted
according to the purpose of site, page, or
pageComponent
The process
Evaluation is ... a semantic activity that needs the
human intervention
-
A possibly automated process for quality
evaluation, using pages and and their components as
elements to evaluate
-
Aimed to relate internal and external
aspects
-
Identification of potential weakness points
-
Subsequent focused analysis (reduced costs,
increased coverage)
-
In depth analysis of source code (including
CSS)
-
Define a model of sites
-
A quality database stores results
-
Expert supplies additional (semantic) info
The (elementary) site model
-
site made of pages
-
page made by components
-
a page component may include other page
components
-
a page is linked to style sheets
-
a style sheet can import other style sheets
Some aspects are ignored
Information stored in the quality database can improve
maintenance
The page components
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type (div, table cell)
-
purpose (header, body, index/menu, footer,
navigation, etc.)
-
number of links (inner, outer, external)
Correctness
-
A merely technical aspect
-
Easy to check
-
Many advantages (maintenance, consistent
behaviour)
-
A not valid page means scarce
attention paid to quality
Automatically checked, at page granularity
Presentation: layout
Immediately perceived by the user (at first
glance the site is ...)
-
simple
-
well structured
-
correct heading tags sequence
-
(float) div better than layout table
-
adaptive layout for different devices
-
consistent style across organisation
(analysis of CSS: how many, cascading,
content)
[back to presentation issues]
Presentation: text
Ease of reading (size, color)
-
foreground/background contrast this is low contrast!
-
colors must differ for more than a single RGB component
-
small fontsize blue is difficult to read this is a small fontsize blue
text!!
-
long uppercase or italic text is difficult to read
-
font must be chosen among the most readable
-
fontsize must be relative
-
not many different fonts in the same page
-
different fonts or fontsize must be meaningful
[back to presentation issues]
Function: essential element or just page
enrichment
-
contrast between foreground image and
background (color or image)
-
flickering or flashing (repeated reading by
screen readers, danger for people affected by
photosensitive epilepsy)
-
number of images in a page and image
sizes (acceptable download time, even when
using low speed connection)
-
image quality (IPR, watermarking);
-
every multimedia component must have a text
equivalent (from a simple description or
synthesis, up to synchronized media equivalents for
time-dependent presentations) depending on the
importance of the multimedia component
[back to presentation issues]
Presentation: links
Essential component - here considered just as far as
presentation is concerned
-
number of links (consider link types and page
purpose)
-
number of broken links (inner, intra,
external)
-
link text (must be understandable out of
context)
[back to presentation issues]
Considering only presentation (accessibility)
issues
-
label positioning
-
text related to each field should appear before
-
text related to check boxes and radio buttons shoud
appear after them
-
explicit associations between labels and form controls
-
field filling with default data
-
appropriate sequence of fields
-
possibility of moving using tab key
Example
[back to presentation issues]
Content
-
Correctness
-
very important in some contexts (e.g. for cultural web
sites)
-
Readability
-
-
not just a recent and web related issue (see Flesh,
and Rudolph, "The Art of Readable
Writing", Macmillan Publishing, 1949)
-
readability index, related to the web site purpose
and user's skill
-
Information architecture
-
-
different difficulty levels
-
summary and details
-
stretchable text
-
user customizable content
-
Information structuring
-
-
number of subheading per heading
-
number of paragraphs per heading
-
mean paragraph length
-
total paragraph length
-
number of sentences in a paragraph
-
Author vs webmaster
Navigation (1)
-
Navigation bar in every page
-
Position in the site
-
Link to home page in every page
-
User is advised of links pointing to external
domains
-
Analysis of link graph (vertical, horizontal,
transverse navigation)
Vertical
Horizontal
Transverse
Navigation (2)
"All the links are equal, but some links are more
equal than others"
-
extensional vs intensional links
-
link to a "concept space" to implement the
cognitive level
-
requires inspection by an expert
-
remains quite subjective
Interaction (form)
-
Transparency
-
user is advised of form filling and submitting
consequences
-
Recovery
-
UNDO
-
in the form page
-
after operation completion, the user is advised of
effects, and undo is possible
-
Annotation
-
user can contribute to the content
Other issues
-
Brand, charisma, graphical
characterization require inspective evaluation
-
Number of supported platforms (cellular
phones, PDA, WebTV)
-
Interface is adaptive and adaptable
(offering of personalized services)
-
last update date
-
author name
-
…
A blueprint (summarizing)
All criteria can be related to some measurable
characteristics
-
Build an abstract model
-
Parse pages
-
many existing tools
-
import/export data (XML)
-
Store results in the Quality Data
Base
-
Process QDB to find existing or potential
quality issues
-
The QDB can be used by the expert as a notepad
-
User tests and task analysis by
appropriate user panels on selected
pages/applications
Conclusion
-
Web site quality
-
scarce attention in the past
-
presently gaining importance
-
Evaluating web sites quality
-
several (mainly qualitative and non orthogonal)
approaches
-
we proposed a quality model based upon a set of
measurable characteristics
-
the model must be tuned (setting range of values)
-
the model can help in improving new sites (use it
as a checklist)
