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GENERATING ACCESSIBLE AND USABLE
INTERNET SYSTEMS
ABSTRACT
In this paper, we describe two Internet development toolkits, which automatically assist developers to build accessible
and usable websites and Internet systems.
KEYWORDS
MDA, UML, Accessibility, Usability, Internet System Design, IDT(Internet Development Toolkit), RNIB(Royal
National Institute for the Blind, UK)
1. INTRODUCTION
The power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect.
Tim Berners-Lee, W3C Director and inventor of the World Wide Web.
The issue of accessibility is one of inclusion, not disability or "the blind". When we use the word "disabled"
we compartmentalize and start talking statistics. Inclusion, sometimes also known as universal design, is
about making the content and functionality of your website available to the widest possible audience. The
fact is that most people who need accessible websites do not consider themselves "disabled."
2. RESEARCHED INTERNET DEVELOPMENT TOOLKIT (IDT)
W3C [2] states that, 10% to 20% of the population in most countries has disabilities.
According to human population statistics, there were 1,206,842,600 disabled people by 2000. It would be
unwise and unlawful to ignore this population. The Disability Rights commissions [3] in UK has launched a
formal investigation into 1000 websites (outcome expected in 2004) just to make sure that organisations
comply with the disability law. The Disability Discrimination Act [6] makes it unlawful for a service
provider to discriminate against a disabled person by refusing to provide any service, which it provides to the
public.
US Census Bureau’s latest survey shows that, people aged 65 and above represents 20% of US population –
currently representing 13%(Estimated total 4.2 million) of the online population. Human aging process
brings vision problems and memory problems among senior users. The Researched Internet Development
also covers accessibility and usability for senior citizen users.
Due to the nature of this conference, we will only discuss few main examples from the Researched Internet
Development Toolkit.
2.1 Why Worry About a Few Blind People?
WHO study in 2002 reveals that there are an estimated 45 million blind people worldwide, while 135 million
more live with low vision, this figure would be doubled by the year 2020. In a study[1] of web sites the
Australian Human Rights and Equal Opportunity Commission pointed out that that a group with accessibility
problems is the aged (HREOC 2000b). This is a group which we all hope to join one day, which is growing
in size and in political and economic power.
RNIB (Royal National Institute for the Blind) sources prove that there are 2m people in UK with sight
problem and every day more than 100 people are registering as blind or sight problem.
2.2 Facilities for Ensuring Accessibility and Usability
The IDT which we have developed enables web site designers to build web pages and sites which satisfy the
W3C requirements for accessibility and usability, these requirements are checked as the designer builds the
pages in the IDT editor, and warnings are issued if the requirements are violated. Some examples of checks
are:
2.2.1 Colour checking
Colour checking facilities of our RIDT makes sure that the colors of the site is usable and accessible by
warning developers if:
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The Background, Foreground or text colour is red or any other non usable and accessible colour.
The Background and Foreground colours are the same.
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The Background and Foreground colours are almost same shade or colour coding.
The Background and Foreground colours have a combination, which does not satisfy accessibility and
usability standard.
Especially any of the following: background, foreground, hyperlink or viewed colour is red. About 10
million American men either cannot distinguish red form green, or see red and green differently from
most people.
Figure 1: Preview of the IDT
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2.2.2 Safe Colour and Colour Palettes
When designing pages, developer should keep in mind that many users view in 256 Colours or less, and that
the colour palettes differ on different platforms and browsers.
Some users may use greyscale or black and white displays, so graphics, which dither badly enough that, they
are undecipherable should be avoided if the developer want to maximise their site's readability for all users.
There are also issues involved in designing pages for readability by colour-blind users.
Research Solution: The IDT Restrict the developers to choose only 256 colours from the colour cube so that
sites are more usable and accessible. Ideally, developers should never use more than five different colours in
one Internet site.
Figure 2: IDT Colour Cube
2.2.3 Preview facilities for Internet Developers
The system provides previewing facilities to display a web page in monochrome, and to display it as it would
be seen by red/green colour-blind people.The different types of preview facilities is provided to help
developers understand that Internet documents appear differently in different browsers, different versions of
the same browser, and even the same version of the same browser on different platforms (e.g. Apple Mac,
Unix). This technique will help the developers to design as universally as possible.
IDT preview facilities
AnyBrowser Campaign
2.2.4 Font Size
Reading time, accuracy and preference test[4] has been carried out with fifteen normal visioned subjectes
ages ranging between 27 and 45 years of age. There are distinct differences in the speed and accuracy with
which users could read various fonts. This test concludes that:
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Small fonts should generally be avoided.
To optimize subjective prefenrence, reading speed and accuracy the best optimal choice is size 10.
Please note that size 10 is for very rare regular vision community. We also noticed that, more than 98%
population of our department is not included in this group.
Text-size facilities of the Internet Development Toolkit
It is recommended that the text for universal Internet sites[5] is to test the pages with default font set to 10, 12
and 14 point to ensure that the design is optimal for these common font sizes. The IDT tool makes sure that
the Internet sites are with this rule by:
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Setting the minimum font size to 12.
Making the developer choose the standard font sizes starting from 12.
2.2.5 Tag
The system also monitors the use of tags to ensure that generated web pages obey the W3C recommendations
for accessibility:
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All images have a ALT attribute
All tables use TH for headers instead of TD, and have an explanatory caption.
The minimum font size used is 12 point.
2.2.6 Copyright
The writer, publisher or the artist has a deep ache to express their own feelings - have gone to the trouble and
expense of searching out and then paying a professional website designer to put together the piece of the
electronic universe. Now whatever it is they wanted to tell everyone is told. The question is: who owns what
everyone is going to see? Does this piece of our heart actually belong to the owner?
The IDT software ensures that developers put their copyright along with correct date and time signature in
every page.
2.2.7 Dreaded Error 404 page
All sites experience some degree of link rot. When users try to go to a non-existent page, they typically see
an unhelpful error message.
The savvy webmaster tries hard to make his/her site visually appealing and easy for visitors to navigate - but
it is also important to be friendly when users visit pages that do not exist on the site.
Of course it is the dreaded Error 404. This is the standard error code that web servers issue when they are
asked to fetch a URL that does not map to an existing resource on the server.
The simplest case is that the URL refers to a static file that no longer exists. Such "link rot" occurs when sites
are reorganised or when old content is deleted. After a page is removed, users continue to follow old
bookmarks, old search engine pointers, old links from other sites, or even old links as printed in a magazine
or book. URLs may also be invalidated for database-driven content; for instance, the exact syntax required to
retrieve a given virtual page may change subtly due to a change in underlying technology.
Finally, sometimes site visitors will guess at a URL of the site, assuming that the web address is a valid path.
Any of these cases leads to an Error 404.
When a Web server receives a request for a non-existent page, by default it returns an Error 404 state code to
the client, and offers explanatory text. The default text is often terse and not very helpful:
Figure 1: Error 404 page
IDT solution for the developer: Developers will have template error 404 page with the following facilities:
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A link to the referring page or a JavaScript "back" link, which is effectively the same as clicking the
back button on your browser.
An opportunity to fix the url by hand in a text box, then be redirected there when the form is submitted.
The url separated out by each directory level, with corresponding links to travel up the hierarchy.
A search box to search the whole site or other sites: Altavista index, the prototype Keywords/A-Z
Directory, or Google.
A graphic image for the frustrated users to have a bit of humour. E.g.
2.2.8 Missing Link
Developers will be able to create the following facilities with the IDT
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ALT line = "..." attribute of <A HREF>
Local search engine to find the product in the local site could be specified.
A global search engine to search for similar product in similar website could also be specified. e.g.
Tesco's missing link can search for similar product in Sainsburys website.
3. SYNTHESIS OF WEB SYSTEMS
A further software toolkit, UML2Web, generates web systems from UML (http://www.omg.org/uml)
descriptions. It can be used in conjunction with the IDT to produce online systems with accessible web page
designs. The UML2Web tool supports:
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Construction of a UML class diagram of the entities and relationships of the data to be recorded and
managed by the system.
Construction of a statechart showing the intended sequence of web pages (represented as states) and
commands (represented as transitions) that will be presented during interaction with the generated
system.
Identification of the use cases, which are selected from operations of editing, creating, listing, deleting,
searching an entity, or adding or removing or retrieving elements of a many-valued association end.
Refinement of the data model, by introduction of primary and foreign keys, by elimination of manymany associations, association classes and inheritance, to place it in a form suitable for implementation
in a relational database.
Automated construction of Java classes which generate the web pages of the system, which include all
input forms corresponding to commands (based on the selected use cases), a login page, a page listing all
commands, and result pages for each query command.
Automated construction of Java servlets, to respond to requests generated from the web pages, and to
enforce the order of actions and web pages described by the statechart specification. The servlets
incorporate type-checking of input data.
Automated generation of a database interface to store and retrieve data.
Both explicit and implicit associations can be used: an explicit association will be implemented using
foreign keys (and an intermediate table in the case of many-many associations), an implicit association
will be implemented using predicates in an SQL SELECT statement.
3.1 Case Study: Property Search System
As an example of the development process for Internet systems, we will construct a system which enables
housebuyers to register their requirements on a website, and then view properties which match their
requirements.
There are two entities:
1.
2.
User, with attributes userName, userEmail, userMinprice, userMaxprice, userArea, userBedrooms,
userType.
Property, with attributes propertyPrice, propertyArea, propertyType, propertyAvailable,
propertyBedrooms.
Some example constraints of this system in LOCA are:
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C1: ``A users minimum price must be at least 0, and less than or equal to their maximum price choice":
0 <= userMinprice & userMinprice <= userMaxprice as a class invariant of User.
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C2: ``A property matches a users requirements if its price is in their range, it is available, has at least as
many bedrooms as they require, and is of the same type and in the same area as required":
userMinprice <= propertyPrice &
userMaxprice >= propertyPrice &
userArea = propertyArea &
userType = propertyType &
userBedrooms <= propertyBedrooms &
propertyAvailable = true
The use cases selected are: createUser, createProperty, getUsermatches.
The class diagram and use cases together constitute a Platform Independent Model (PIM) in the terms of
the MDA (omg.org/mda). A statechart is not included, so a default interaction sequence for the system will
be produced, in which the interaction flow returns to the command page after the processing of each
command (input form, followed by result page for query operations) is completed.
A Platform Specific Model (PSM) can now be produced for whichever web system platform is to be used:
currently only a Java and HTML platform using an MVC architecture is supported, although it is intended
to support J2EE, .Net and Web Service platforms.
For each use case a derived class is produced which describes the input HTML form needed to enter data
for the use case. For create and edit operations this class/form has a field for each attribute of the entity to
be created/edited. For the get operation only the primary key of the entity owning the role is required. For
create and edit the local class invariants of the PIM entity, such as C1, are copied to the new class, and
represent properties to be checked by client-side scripts before form data is submitted to the server.
The following generated components are then produced from the PIM and PSM:
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Web page generation classes createUserPage, createPropertyPage, LoginPage, CommandPage,
getUsematchesPage, which have a method getHtml(): String that returns the corresponding web pages
as HTML text.
Servlet classes createUserServlet, createPropertyServlet, CommandServlet, getUsermatchesServlet,
LoginServlet, which process the operation requests from the corresponding web pages. These also
check class invariants (in the case of create and edit operations) before data is submitted to the
database.
A web-page generation class PropertyResults for producing a web page, which shows the results of the
getUsermatches operation, as a list of table rows.
A database interface Dbi, which uses SQL statements to access and modify the database using Java
JDBC. The SQL statements for the getUsermatches and createUser operations are:
getMatches(nme,eml):
SELECT propertyId, propertyPrice, propertyType,
propertyArea, propertyAvailable, propertyBedrooms
FROM User, Property WHERE
userName = nme AND userEmail = eml AND
userMinprice <= propertyPrice AND
userMaxprice >= propertyPrice AND
userArea = propertyArea AND
userType = propertyType AND
propertyAvailable = `true' AND
userBedrooms <= propertyBedrooms
createUser(nme,eml,minp,maxp,typ,bed,ar):
INSERT INTO User VALUES (id,nme,eml,minp,maxp,typ,bed,ar)
The form of the SELECT statement for getUsermatches is directly derived from the constraint C2 that
defines the implicit association between users and properties.
4. RESEARCH OUTCOME
Since there are very few/no researches in this area, an overwhelming number of commercial organisations in
UK approached RNIB to make their sites accessible. They do not want to lose out on 8.5 million disabled
customers, not to mention their friends, relatives and carers. If all the bodies and people involved in
commissioning, publishing and designing web sites were to make these sites more accessible for people with
disabilities, they also would make them much more accessible for people without disability. [5] If the
accessibility of a site is improved, the usability is automatically improved – n ot just for disabled people, but
for the wider audience as well.
There is a WASP(Web Standard Project) Action Campaigns works with website developers and the makers
of visual editing environments to use and promote the use of standards. W3C also has set up sets of rules for
Internet development – developers who are aware of these standard are trying very hard to keep up to it.
Sometimes, they have to convince their employer to spend extra funding for accessibility and usability. The
researched toolkit we have described in this paper have those facilities auto-built.
There also been some campaign from the public [anybrowser.org] to make Internet sites appear same in
different browser. The IDT software have the preview facilities, which will help the developers to overcome
this problem.
An Italian inventor invented built the first typewriter to help a blind countess, telephone originally invented
for people hard of hearing, remote control was invented for people with limited mobility, scanner evolved
from technologies to make talking book for Blinds. Only time can answer what accessibility and usability
will lead us.
5. CONCLUSION
// Clearly indicate advantages, limitations and possible applications.
We have described two linked toolsets, which assist developers in producing accessible, usable and error-free
web sites and Internet systems. Future work will extend the UML2Web tool to produce code for a wider
range of platforms, and to incorporate web service delivery and usage. These toolkits are an advance on the
state of the art by explicitly considering accessibility issues, and in the case of UML2Web, by use of formal
model constraints to generate correct Internet system code in accordance with the OMG MDA principles.
REFERENCES
References and Citations should follow the Harvard (or author-date) system convention. Check the examples. If a
referenced paper has three or more authors the reference should always appear as the first author followed by et al.
Toolkit
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Book
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