Part of Item:
Comment Type: substantive
Comment (including rationale for proposed change):
The definition of Web unit is still ambiguous.
(1) If an HTML document (home.htm) has various linked stylesheets (one for screen, one for print, one for projection, ...), these are not all intended to be rendered together. I think the the following would all count as Web units:
- home.htm with the CSS for \'screen\',
- home.htm with the CSS for \'projection\',
- home.htm with the CSS for \'braille\',
- home.htm with the CSS for \'aural\',
However, this is not clear from the definition. If these are all different web units, it is also impossible to identify them with a URL, because the URL is the same for each.
(2) If an HTML page uses an object element with one or more fallbacks nested inside it (see the example slightly below http://www.w3.org/TR/1999/REC-html401-19991224/struct/objects.html#idx-object-5), I think the Web unit you claim conformance for is the HTML document with the outermost object element (with the TheEarth.py applet). However, the content of each of the nested object elements is not meant to be rendered together with the content of all the other object elements. Does that mean that there is a different web unit per fallback/nested object element?
(3) If a web page uses frames, the content of some of the frames depends on the user\'s interaction: e.g. clicking a link in the navigation frame opens a different document in the content frame. So the URL that identifies the frameset document does not always identify the same Web unit, unless the Web unit is limited to what is loaded by default.
(4) If user agent X requests URL http://www.example.com/ with MIME type aaa/bbb and user agent Y requests the same URL with MIME type ccc/ddd, and they get different web units because of the different MIME type, the URL cannot be used to differentiate between the two web units. Does that mean these are different Web units according to the current definition?
Most of this was previously discussed on the ERT mailing list in the context of conformance claims (see http://lists.w3.org/Archives/Public/public-wai-ert/2006May/0029.html and next messages in the same thread) and forwarded to the GL list (http://lists.w3.org/Archives/Public/w3c-wai-gl/2006AprJun/0181.html).
We have revised the guidelines and eliminated the word "Web unit" in favor of "Web page." We have defined "Web page"as follows (see http://www.w3.org/TR/2007/WD-WCAG20-20070517/#webpagedef ):
a resource that is referenced by a URI and is not embedded in another resource, plus any other resources that are used in the rendering or intended to be rendered together with it
Note: Although any "other resources" would be rendered together with the primary resource, they would not necessarily be rendered simultaneously with each other.
Example 1: When you enter http://shopping.example.com/ in your browser you enter a movie-like interactive shopping environment where you visually move about a store dragging products off of the shelves around you into a visual shopping cart in front of you. Clicking on a product causes it to be demonstrated with a specification sheet floating alongside.
Example 2: A Web resource including all embedded images and media.
Example 4: A customizable portal site, where users can choose content to display from a set of different content modules.
To answer your questions:
According to our definition.
#1 - They are all the same Web page because they are all the same primary resource with different secondary resources rendered with them.
#2 Again they are all the same Web page including all the nested versions. The secondary resources do not need to be rendered simultaneously with each other, only with the primary, to be part of the same Web page.
Regarding your concern #3, the definition of Web page is purposefully written to include dynamic content that comes from the same URI. So all of the content from all the variations would be part of the web page. If the contents of the frames can be loaded separately as well, then they would also be separate Web pages as well. But they would still be part of the frame Web page.
#4 If the different mime type would cause a different PRIMARY resource to be loaded, then they would be different Web pages. If you included that URI in your claim, all Web pages from that URI would have to be conform (meet the success criterion or have a mechanism to obtain a page with the same content that did).