UKOLN AHDS Tangram Model For Web Accessibility


This document describes a user-focussed approach to Web accessibility in which the conventional approach to Web accessibility (based on use of WAI WCAG guidelines) can be applied within a wider context.

Traditional Approach To Web Accessibility

The conventional approach to Web accessibility is normally assumed to be provided by implementation of the Web Content Accessibility Guidelines (WCAG) which have been developed by the Web Accessibility Initiative (WAI).

In fact the WCAG guidelines are part of a set of three guidelines developed by WAI, the other guidelines being the Authoring Tools Accessibility Guidelines (ATAG) and the User Agent Accessibility Guidelines (UAAG). The WAI approach is reliant on full implementation of these three sets of guidelines.

Limitations Of The WAI Approach

Although WAI has been a political success, with an appreciation of the importance of Web accessibility now widely acknowledged, and has provided a useful set of guidelines which can help Web developers produce more accessible Web sites, the WAI model and the individual guidelines have their flaws, as described by Kelly et al [1]:

The Tangram Model

Although the WAI approach has its flaws (which is understandable as this was an initial attempt to address a very difficult area) it needs to be recognised that WCAG guidelines are valuable. The challenge is to develop an approach which makes use of useful WCAG guidelines in a way which can be integrated with others areas of best practices (e.g. including usability, interoperability, etc.) and provides a richer and more usable and accessible experience to the target user community.

In the tangram model for Web accessibility (developed by Sloan, Kelly et al [3]) each piece in the tangram (see below left) represents guidelines in areas such as accessibility, usability, interoperability, etc. The challenge for the Web developer is to develop a solution which is 'pleasing' to the target user community (see below right).

Tangram model

The tangram model provides several benefits:


  1. Forcing Standardization or Accommodating Diversity? A Framework for Applying the WCAG in the Real World, Kelly, Sloan et al, Proceedings of the 2005 International Cross-Disciplinary Workshop on Web Accessibility (W4A),
  2. Developing A Holistic Approach For E-Learning Accessibility, Kelly, Phipps and Swift, CJLT 2004, 3(1),
  3. Contextual Web Accessibility - Maximizing the Benefit of Accessibility Guidelines, Sloan, et al, Proceedings of the 2006 International Cross-Disciplinary Workshop on Web Accessibility (W4A),