Re: Question about "Implicit value for Role"

Hi Matt,

> I still do not understand the original question given the example. I 
> didn't even realize that there was a concept of value associated with 
> ARIA roles., e.g., Alert has a value of assertive? Isn't it the live 
> property that has the value, not the assertive role?

The full definition of "Implicit Value for Role is in section 5.2.9 [1].

Some roles have inherent states and properties.  An alert is a "... type 
of live region..." [2], so it conceptually has an aria-live property.

The point of the "implicit value for role" entry is:  if the author does 
not provide that state or property, what is its implied value? Or, how 
will user agents map inherent states/properties to the accessibility 
API?  Sometimes, they will use the default value, which, in the case of 
aria-live is "off" [3].  However, the alert role is further defined as a 
live region  " ... with important, and usually time-sensitive, 
information".  The point being, an alert is assertive -- the rationale 
of using an alert is to, well, alert the user.  Using the default value 
of aria-live="none" with an alert defeats the purpose of having an alert 
in the first place.  Thus, when aria-live is missing where role="alert" 
is used, it has an implicit value of "assertive", not "none".

Of course, the author can decide that some alerts are less important 
than others, and choose to explicitly provide an aria-live property with 
a value of, say, "polite".

[1] http://w3c.github.io/aria/aria/aria.html#implictValueForRole
[2] http://w3c.github.io/aria/aria/aria.html#alert
[3] http://w3c.github.io/aria/aria/aria.html#aria-live

-- 
;;;;joseph.

'Array(16).join("wat" - 1) + " Batman!"'
            - G. Bernhardt -

Received on Tuesday, 24 March 2015 14:53:31 UTC