Rating Algorithm for Evaluation of Web Pages

Abstract

This document describes the algorithm by which evaluating tools will rate accessibility of web pages. It combines automatic checks with explicity confirmations by the tool user that manual checks have been passed. It is based on The WAI Web Content Accessibility Guidelines.

Status Of This Document

This is a working draft.

A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR.

This document has been produced as part of the W3C Web Accessibility Initiative.

Introduction

The Web Content Accessibility Guidelines define overall ratings for web pages. Tools to apply these definitions to web pages require a combination of automatic and manual techniques. This note defines an algorithm by which the tool may combine the automatic and manual ratings.

Rating Algorithm

Rating shall proceed as follows:

1. The tool shall offer the manual and automatic checks defined in the Evaluation and Repair Techniques Document".
2. The tool shall give the user the option to manually check all items on the web page that require manual checking. Irrelevant items shall be omitted (e.g. if there is no audio or video, manual checking of the textual equivalents is irrelevant.) All manual checkoff shall require an explicit action by the user for each item the user asserts satisfies the guidelines (e.g. for each image, there shall be means for the user to assert that the ALT text is suitable.).
3. If the user applies all the manual checkoff procedures relevant to the page The tool shall use this information together with its automatic checking to give the page an A, AA, or AAA rating, per the Web Content Accessibility Guidelines (viz. "A", "AA", "AAA" if the "web site" satisfied all priority 1, 1+2, 1+2+3 checkpoints respectively).
4. If the user does not use the manual checkoff procedure at all, the tool shall make statements or their equivalents as follows:

   Note that these are only suggested wordings. Any wording that means the same is acceptable.

   • If any Priority 1 automatic checkpoints failed, say "This site is not accessible."
   • Otherwise say "This site might be accessible. Further (manual) checks are needed to properly gauge accessibility."
5. If the user performs all manual priority 1 checkpoints, and all manual and automatic priority 1 checkpoints are passed, say "This site has at least an A accessibilty rating. Manual checks are needed to see if it passes the higher AA or AAA standards"
6. If the user performs all manual priority 1 and 2 checkpoints, and all manual and automatic priority 1 and 2 checkpoints are passed, say "This site has at least an AA accessibilty rating. Manual checks are needed to see if it passes the higher AAA standard"

Issues

1. How to define accessibility of a "web site". This requires that we define "web site".