louis@perrochon.com
Andrea Kennel,
Institut für Informationssysteme,
ETH Zürich,
Switzerland.
kennel@inf.ethz.ch
Titel level 2 1. Introduction
Ref to Titel level 3
Blind users cannot use a state-of-the art mouse because a mouse normally
requires visual feedback from the screen to the user. As a
consequence, when working with hypertexts, blind users cannot simply
click on a magic blue word in the middle of the screen. Normally they
have to search for it word by word using a screen reader.
Another general problem is that blind users cannot get an overview of the structure of a text with one quick glance at the screen. Thus blind users can be "lost in hyperspace" very quick.
Of course the correct solution is building better screen
readers. However this is not that easy. We present a simple solution
that solves some of these problems for W3-access. Section 2
gives a short overview over the architecture. Section 3 presents the users
view of our system. section 4 gives some technical details for those
who want to provide this new service to blind users.
Titel level 2 2. Architecture
Ref to Titel level 3
We insert a transformer between the W3-browser and the W3-server. The
transformer modifies each document to reflect its structure
clearer. Fortunately, we did not have to build everything from
scratch. A proxy server was the ideal environment for our
project. Thus the CERN-httpd has been modified to provide this
additional functionality. The resulting architecture is described in
Fig. 1
Image "arch.gif"
Fig. 1 Architecture of 'W3-Access for Blinds'
The process of fetching a document has has 6 steps.
Immediately after loading a document, the user should be able to jump
to the list of links to have an idea of the links available in this
document. Interesting links can then be activated immediately. To
achieve this, the very first reference at the top of each modified
document is a reference to the list of links at the end of the
modified document. This reference is named 'Ref to Linklist'. After
activation of this reference, the beginning of the list of links will
appear at the top of the browser window. The first entry of the list
of links indicates the number of links in the list. The following
entries in the list are copies of all the links in the original
document. The very last entry in the list is named 'Ref to Top' and
points back to the top of the modified document. The list is
terminated by the words 'End of Linklist'.
Titel level 3 3.3 The List of Titles
Ref to Titel level 4
Image "titles.gif"
Fig. 3 The list of titles in a document with two levels of titles.
(Not all the references are shown.)
Most hypertexts have a hierarchical title structure: titles of level one (<H1>) contain several titles of level two (<h2>) which contain subtitles of level three (<h3>) and so on. In a hypertext, the blind user can get a quick overview just by browsing through the titles of level one (<H1>). This is why a nested list of all the titles is added to the original document.
Additionally, the entries in the list of titles are references to the
titles in the text. Thus interesting titles in the text can
immediately be found. Another possibility is to go down
the title hierarchy and find all subtitles of this title. The list of
titles is terminated by the words 'End of titlelist'.
Titel level 4 3.3.1 Jumping from the Text to the Titlelist
Ref to Titel level 5
A reference named 'Ref to title level1' at the top of the modified
document (just after 'Ref to Linklist') points to the list of level 1
titles. At the beginning of each list of titles, the number of titles
in this list is inserted. After each title in the text, there is a
reference to the corresponding list of all subtitles .
Titel level 4 3.3.2 Navigating inside the List of Titles
Ref to Titel level 5
After each entry in the list of titles there is a reference to the
'Lower level'. This reference points to the list of subtitles
belonging to the title. If there are no more subtitles this reference
will not appear in the list. At the end of the lists of level 2-7,
there will also be a reference to the 'Upper level'.
Titel level 4 3.3.3 Jumping From the List of Titles Back to the Text:
Ref to Titel level 5
Each entry in the list is a reference to the corresponding title. At
the end of each titlelist there are references named 'Back to Text'
and 'Top of Document'. 'Top of Document' points to the top of the
document, 'Back to Text' to the title to which the current list
belongs.
Titel level 3 3.4 More Features
Ref to Titel level 4
Titel level 4 3.4.1 Forms
Ref to Titel level 5
The original document is not only enriched with additional links. It
is also modified. The corresponding keyword 'Image', 'Radiobutton',
'Checkbox', 'Editfield', 'Button' and 'Combobox' is inserted before
each of those HTML elements in the document. Thus the user is
informed that non-textual elements appear, even if the screen reader
does not identify them.
Titel level 4 3.4.2 Searching
Ref to Titel level 5
In the text of a document the keyword 'link' is inserted before each
link. Some Screen readers support "find"-commands, which
can now be used to jump from link to link. Similarly the keywords
'title level' can be used to jump from one title to the next. There
are some other possible targets for searches that are
self-explanatory: 'Image', 'Radiobutton', 'Checkbox', 'Editfield',
'Button' and 'Combobox'.
Titel level 2 4. The provider's view
Ref to Titel level 3
The user doesn't have to install any software. Anybody can use the
proxy server running at ETH Zurich (<http://ea.ethz.ch:8080/>,
in Switzerland). However, it might be wise to set up more
proxies. They will reduce network traffic, as everybody can access the
nearest proxy.
The proxy-server is a modified CERN-httpd-daemon. The provider has to add one line to the proxy code and change one line in the makefile. Of course some files of ours have to be added to the files of the distribution, too. After compilation, the httpd is started in proxy-only mode.
Our proxy-server is configurable. There are two files, that control
the transformation process. One is used to define all the keywords,
that are inserted into the HTML documents in front of special HTML
elements, the other defines the transformation of each HTML
element. See the documentation for more details on how to configure
the proxy. (Our code will be freely available by End of August)
Titel level 2 5. Future Work
Ref to Titel level 3
We have to get more experience and user feedback, to do better and
additional transformation.
The idea of making structure information in hypertexts better visible might prove useful for all users of hypertext. A feature, that automatically builds tables of contents and lists of links is useful for all kinds of hypertext systems. Such lists might soon be a useful feature in every browser.
Browsers should use standard elements for forms (buttons, etc.), so the screen readers have a chance to recognise them. Under MS Windows Netscape and Mosaic do not use the standard system elements. WinWeb uses standard elements and outSPOKEN for Windows recognises all of them.
Correct and "good" HTML is very important! If our proxy server gets a HTML document with <bold>-tags instead of <h3>-tags, it will not recognise the titles.
Titel level 2 6. Summary
Ref to Titel level 3
When a user loads a document via our proxy-server, a list of links and
a nested list of titles are added to the requested document. These
lists give a quick overview over the document. They can also be used
to navigate quickly through the document and to follow interesting
links. The list of titles has a hierarchical structure (like a
tree). The user can browse through this structure using the links
'Lower level' and 'Upper level'. To return to the text the references
to the titles or the references 'Top' or 'Back' are used.
Titel level 2 7. Acknowledgements
Ref to Titel level 3
Thanks to Markus Ullius, Markus Marti, Albert Bosshard and Willi Roman
who did the implementation as a student-project. And thanks to Alireza
Darvishi for testing the new user interface and providing useful input
on the problems of blind users.