schema - http://www.esd.org.uk/standards/egms/3.0/egms%2Dschema/
from Andrew Wilson issues paper for as 5044:
Element Name:   Accessibility
  Namespace:   eGMS.
                                 http://www.esd.org.uk/standards/egms/3.0/egms-schema#
Label:   Accessibility
Type:   Element
eGMS definition:   Indicates the resource’s
availability and usability to specific groups, in particular
people with disabilities and users of filtering software.
Comment:   The values assigned to
this tag will assert compliance with usability and accessibility
standards.
Obligation:   Internet Content Rating
Association rating and conformance with W3C Content Accessibility
Guidelines is Mandatory for resources to be published on any
public website. Other tags Recommended as appropriate.
ICRA – http://www.icra.org
    WCAG - http://www.w3.org/TR/WAI-WEBCONTENT/
    RNIB  -
    http://www.rnib.org.uk/digital/siraccess/welcome.htm 
    Notes:   Accessibility indicates
    whether particular users will be able to access or use the
    resource. Rights indicates if they are allowed to.
  The
  eGMS standard claims that “some filtering software designed
  to protect children will in future not allow access to any
  site that does not have a suitable ICRA rating”.  
ICRA labels are expressed using RDF. See example in Appendix
  A.
    Examples:   <META NAME="AGLS.accessibility" scheme="WCAG" content="Double-A">
  <agls:accessibility>
     Bobby accredited
  </agls:accessibility>