Re: bug Bug 11891 - add role attribute to list of global attributes and add definition for it (part of Issue 199)

Benjamin Hawkes-Lewis wrote:
> On Fri, Jan 27, 2012 at 3:53 PM, Richard Schwerdtfeger
> <schwer@us.ibm.com> wrote:
>   
> Seems reasonable. Where does the WAI-ARIA spec define valid role tokens, though?
>   
I would point to the "Role Attribute" section of the ARIA spec:
http://www.w3.org/TR/wai-aria/host_languages#host_general_role
> For example, how would an HTML conformance checker determine if
> "accordion" is a valid role token?
>
> The spec defines some roles, but also says user agents may extend them
> with new roles and that future specs will define how to use these new
> roles interoperably. 
The Role Attribute section above requires that the role attribute accept
*at least* the concrete ARIA roles as values. It does not impose
requirements one way or the other about other values, including abstract
ARIA roles. It does define that the first *recognized* token is the one
used for mapping to the Accessibility API, at which point the WAI-ARIA
1.0 User Agent Implementation Guide
http://www.w3.org/TR/wai-aria-implementation/ takes over. This does not
require that the first token be the one authors expect will be used - if
there is an ARIA 2.0, authors may want to use an ARIA 2.0 token first as
the preferred role, and an ARIA 1.0 role as a second token as a backup
for user agents that haven't updated yet. ARIA 1.0 user agents would
just see the first token is unrecognized and discard it, and use the
second. It may be that HTML 5 will be locked to ARIA 1.0, but that may
not necessarily be the case by the time it reaches Rec status, and
anyway hopefully the "Living Standard" version of HTML would seamlessly
support any further versions of ARIA that come along.
> It does say that "Content authors MUST NOT use
> abstract roles because they are not implemented in the API binding".
>   
There are no user agent constraints on abstract roles. User agents don't
know that abstract roles are abstract, they just know they don't have a
defined mapping for them. That's why there's an author prohibition on
using those (since it's useless) but not a user agent requirement.
> Should HTML conformance checkers:
>
> 1. Allow any token that is not an abstract role defined in WAI-ARIA
> (e.g. allow "accordion" and "checkbox" but forbid "input"?
>   
Conformance checkers should *allow* any token that meets the lexical
requirements, i.e., doesn't have characters forbidden to a token in a
token list. If conformance checkers are checking only for ARIA roles, it
would be appropriate to *warn* about unrecognized tokens (including
abstract roles). However, because the ARIA spec doesn't require that the
role attribute contain only ARIA roles, and the XHTML Vocabulary defines
additional ones, it may not be appropriate for conformance checkers to
give this warning, unless the HTML spec wishes to constrain the role
attribute to contain ARIA roles. The accessibility community wouldn't
have a problem with this, but others may, so I recommend not introducing
that constraint.
> 2. Reject any token that is an abstract role defined in WAI-ARIA and
> additionally require the token list to begin with a concrete role
> defined in WAI-ARIA (e.g. allow "accordion" and "checkbox" but require
> "checkbox" to come first).
>   
Definitely should not require the token list to begin with a concrete
role [from ARIA 1.0], because the first token might be a concrete role
from a future version of ARIA and should be valid from a forwards
compatibility perspective. Same as above on warn, not reject, of
unrecognized / unmapped tokens.
> 3. Reject any token that is not a concrete role defined in WAI-ARIA
> (e.g. reject "accordion" and "input" whereever they occur in the token
> list)?
>   
Same as above on warn, not reject, of unrecognized / unmapped tokens.
> Whichever way, it would probably be best to be explicit.
>   
Agree.

Michael
-- 

Michael Cooper
Web Accessibility Specialist
World Wide Web Consortium, Web Accessibility Initiative
E-mail cooper@w3.org <mailto:cooper@w3.org>
Information Page <http://www.w3.org/People/cooper/>