WCAG 2.0 Baseline Concept
http://juicystudio.com/article/wcag-baseline-concept.php

Lemon, Gez
Juicy Studio
2006

Abstract:

In order to encourage vendors of non-W3C technologies to include accessibility features in their technologies, and in recognition of emerging technologies that are beneficial for the Web, WCAG 2.0 is technology neutral. Rather than list each technology that the guidelines cover, WCAG 2.0 introduces the concept of a baseline. This post attempts to explain what is meant by this baseline concept.