[whatwg] HTML5: New link-types regarding guideline 2.4 in WCAG 2.0

[Lachlan Hunt]

Anne van Kesteren wrote:
> What would be the combined semantics of |rel="index prev"| or |rel="prev index"|...

That the resource provides an index for the current document and is the 
previous document in sequence.

eg.  If all the files of a short online book, in this order, were:

1. contents.html
2. chapter1.html
3. chapter2.html
4. book-index.html
5. colophon.html

(That would be the order they appear in a printed/published book version 
too)

Using only the next, prev and index attributes, all the possible links 
(that I can think of) could be:

contents.html:
   <!-- first document in sequence, no prev -->
   <link rel="next" href="chapter1.html">
   <link rel="index" href="book-index.html">

chapter1.html:
   <link rel="prev" href="contents.html">
   <link rel="next" href="chapter2.html">
   <link rel="index" href="book-index.html">

chapter2.html:
   <link rel="prev" href="chapter1.html">
   <link rel="next index" href="book-index.html">

book-index.html:
   <link rel="prev" href="chapter2.html">
   <link rel="next" href="colophon.html">

colophon.html:
   <link rel="prev index" href="book-index.html">
   <!-- last document in sequence, no next -->

(title, rev, and rel="contents" attributes have been omitted for 
simplicity.  Hixie, feel free to use that example in the spec if you like)

Each of those points to the next and previous documents in sequence 
(except for the contents and colophon).  Each of them also points to the 
document serving as the index (book-index.html).  For chapter2.html, 
since book-index.html is both the next document in sequence and the 
document serving as the index, it can be combined into the one link 
element with the two relationships, rather than two seperate 
relationships like the other pages.  Same applies to colophon.html, 
except using prev instead.

Are any of those examples above, with either individual or combined 
relationships, semantically incorrect?  Is there anything I haven't 
explained well enough?

-- 
Lachlan Hunt
http://lachy.id.au/
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