The type attribute currently allows the designated value "application/atom+xml" to be any case. This is consistent with other uses of type, but current autodiscovery implementations largely stick to all-lowercase: type="application/atom+xml". I propose that the type attribute be less permissive for Atom autodiscovery than other uses of the attribute in HTML and XHTML links.
Proposed language for Section 4.2:
The media type for Atom is "application/atom+xml" [I-D.ietf-atompub-format], so in an Atom autodiscovery element the value of the type attribute MUST contain the string "application/atom+xml" in lowercase. (This differs from other uses of the link element that permit the attribute's value to be uppercase, lowercase, or mixed case.)
Adopting this change would enable Section 7.2, type 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.