A Unified Ontology-Based Web Page Model For Improving
Accessibility
Ruslan R. Fayzrakhmanov
Max C. GöbelWolfgang Holzinger
Bernhard Krüpl
Inst. of Information Systems, DBAI Group
TU Wien, Austria
Robert Baumgartner
Lixto Software GmbH
Vienna, Austria
ABSTRACT
Fast technological advancements and little compliance with
accessibility standards by Web page authors pose serious ob-
stacles to the Web experience of the blind user. We propose
a unified Web document model that enables us to create
a richer browsing experience and improved navigability for
blind users. The model provides an integrated view on all
aspects of a Web page and is leveraged to create a multi-
axial user interface.
Categories and Subject Descriptors: H.5.2 [Informa-
tion Interfaces and Presentation]: User Interfaces
General Terms: Design, Human Factors, Experimenta-
tion.
Keywords: Web Accessibility.
1. INTRODUCTION
Web accessibility research is strongly focused on the au-
thoring process (WCAG, WAI-ARIA, etc.) of Web docu-
ments. Yet only a small percentage of Web sites implement
the proposed standards and new technologies require long
adoption times for accessibility. While we fully acknowledge
the important work in creating and implementing standards
for Web accessibility, we see our focus in those websites that,
deliberately or not, do not adhere to these standards and are
currently hard to read by visually impaired users.
In the ABBA1 project, we focus on improving the navi-
gability of a Web document for the visually impaired user.
Other interesting readings on the topic can be found at [2,
3]. We propose a highly efficient, multi-axial serialization
framework to help the user to get a better cognitive under-
standing of a Web resource and to be able to navigate on
that resource more efficiently.
Central to our navigation framework is the transformation
of the original HTML format of a Web document into a
rich document representation — encapsulating on top of the
parsed DOM tree structure a wide set of implicit visual and
semantic page properties in a queryable form. This allows
to reason more fully over structure, content and interactive
1The ABBA project (Advanced Barrier-free Browser
Accessibility) is sponsored by the Austrian Forschungs-
fo¨rderungsgesellschaft FFG under grant 819563.
Copyright is held by the author/owner(s).
WWW 2010, April 26–30, 2010, Raleigh, North Carolina, USA.
ACM 978-1-60558-799-8/10/04.
DOM Layout
Tables
Columns Topology Appearance
Content
color font
NLP
concepts
well
known
formats
domain
specific
concepts
raw
text
ids
classes
neighbor
hood
alignment stacking grouping
segmentation
manual and
automatic
annotation
table
recognition
record
recognition
traditional
wrappers
Figure 1: Unified Ontological Model
functionality of the document and to deduce a wider set of
serializations thereof.
In this paper we describe the transformation process as a
combination of a number of structural and semantic enrich-
ers and argue that the expressiveness of the resulting model
is superior for document serialization to existing approaches.
Finally, we present a multi-axial serialization framework that
encapsulates the document model into a simple user inter-
face that supports the visually impaired (VI) user in under-
standing a document and finding required information more
effectively.
2. THEUNIFIEDONTOLOGICALMODEL
Our core innovation towards improving Web navigability
for VI users is the introduction of a unified ontological model
that i) integrates the descriptions of all aspects of a Web
page into one model, and ii) hides away all implementation
details from its authoring process. The unified model is a
conglomerate of several specialized ontologies providing us
with a rich set of concepts for the description of the build-
ing blocks on a Web page (words, images, form elements,
but also more abstract patterns such as columns) with their
properties (coordinates, size, font formatting) and relations
(topological, semantical).
Figure 1 shows a top-level outline of the main constituents
of the unified model. Boxed elements show sub-ontologies
and concepts, cloud shapes indicate algorithms and heuris-
tics that work on them.
For instance, the DOM ontology fragment contains data
that is fetched from the live page model of a Web browser.
It enables traditional DOM tree based segmentation. The
layout ontology fragment describes the visual appearance of
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