The rel attribute currently allows "alternate" to be any case and part of a list of multiple keywords. This is consistent with other uses of rel, but current autodiscovery implementations stick to the simplest construction: rel="alternate". I propose that the rel attribute be less permissive for Atom autodiscovery than other uses of the rel attribute in HTML and XHTML links.
Proposed language for Section 4.1:
The rel attribute MUST be present in an Atom autodiscovery element and have a value of "alternate" in lowercase. This keyword signifies that the feed represented by the link element is an alternate form of the web page's content. Though for other purposes a link element's rel attribute MAY contain a space-separated list of keywords in uppercase, lowercase, or mixed case, for autodiscovery it MUST be a single keyword and lowercase.
Adopting this change would enable Section 7.3, rel attribute variations, to be deleted.
This approach is consistent with the RSS Autodiscovery specification recently published by the RSS Advisory Board:
Ideally, the two groups will ultimately offer the same guidance on autodiscovery. Whether that means Atom follows the RSS lead or vice versa is an open subject.