Re: 4.1.1 Parsing in WCAG 2.0 and 2.1

Hey Andrew,

>  I think that is difficult to reconcile with the SC text. I don’t think
that the specification allows duplicate ids, nor is there any error
correction for it – it just isn’t impactful consistently, and where it is
that impact is addressed by a different SC.

It's not in the HTML definition of Unique Identifier, true, but it is
defined for all attributes that reference IDs. ARIA WG put it in Core AAM
(previously ARIA User Agent Guide), and have also added it in to ARIA 1.2:

https://www.w3.org/TR/wai-aria-implementation-1.0/#mapping_additional_relations_error_processing
https://www.w3.org/TR/core-aam/#mapping_additional_relations_error_processing
https://www.w3.org/TR/wai-aria-1.2/#mapping_additional_relations_error_processing
> If more than one element has the same ID, the user agent SHOULD use the
first element found with the given ID

And in HTML the <label> for attribute has the following text:

https://html.spec.whatwg.org/#the-label-element
> If the attribute is specified and there is an element in the tree whose
ID is equal to the value of the for attribute, and the first such element
in tree order is a labelable element, then that element is the label
element's labeled control.

To me that feels like enough "error correct" for duplicate IDs to fall
under the exception of SC 4.1.1. Genuinely, there are lots of ways browsers
could have done this had this not been standardized. I still regularly get
asked why the IDs on elements hidden with CSS still don't get ignored.
Browsers could have done that, but none of them do. HTML and ARIA say
they're not supposed to.


On Fri, Mar 10, 2023 at 4:17 PM Andrew Kirkpatrick <akirkpat@adobe.com>
wrote:

> I think Wilco’s suggestion was that you wouldn’t need to update the
> conformance model, you just consider it ‘passed’ (assuming you’re using
> HTML based content) as “specifications allow these features”.
>
> https://lists.w3.org/Archives/Public/w3c-wai-gl/2023JanMar/0245.html
> <https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.w3.org%2FArchives%2FPublic%2Fw3c-wai-gl%2F2023JanMar%2F0245.html&data=05%7C01%7Cakirkpat%40adobe.com%7C7f4d9bf4899f485834a408db2179a362%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C638140578539730415%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=L6jVQcGdrVPjaL8oC2%2BSfGs7la9S5IoibtYQERK%2B%2FJg%3D&reserved=0>
>
>
>
> I think that is difficult to reconcile with the SC text. I don’t think
> that the specification allows duplicate ids, nor is there any error
> correction for it – it just isn’t impactful consistently, and where it is
> that impact is addressed by a different SC.
>
>
>
> *4.1.1 Parsing:* In content implemented using markup languages, elements
> have complete start and end tags, elements are nested according to their
> specifications, elements do not contain duplicate attributes, and any IDs
> are unique, except where the specifications allow these features. (Level A)
>
>
>
> AWK
>


-- 
*Wilco Fiers*
Axe-core & Axe-linter product owner - WCAG 3 Project Manager - Facilitator
ACT Task Force