HTML and CSS Reference
Percent-encoding , the mechanism that encodes certain characters of a URI using a string that begins with a
percent sign ( % ), 2 should be eliminated whenever possible. 3 Dots should be avoided in URIs. The Internationalized
Resource Identifier should be NFC normalized, or NFKC normalized. Empty fragment identifiers should be preserved.
The URIs in id elements are case-sensitive. Identifiers that apply percent-escaping are considered different from the
ones that do not when comparing id instances.
The link Element
External hyperlinks related to an Atom entry or the whole feed can be provided by the link element. This
element has six attributes: href , rel , type , hreflang , title , and length . The required href attribute contains the
Internationalized Resource Identifier of the link. The optional rel attribute must have a nonempty string as a value
according to either the IRI or the isegment-nz-nc syntax rules of RFC 3987. Allowed values are alternate , related ,
self , enclosure , and via . The type attribute, which is optional, must have a MIME media type as its value. The
hreflang attribute is also optional. When provided, it must have an RFC 3066 language tag. The optional title
attribute is language-sensitive. Character entities used in the title are considered characters instead of markup, and
displayed rather than processed. A hint on the advisory length of the linked content can be provided by the optional
length attribute in octets. Listing 8-42 shows a typical link element.
Listing 8-42. A link Element in Atom
<link rel="self" type="application/atom+xml" href="http://example.net/atom.xml" />
The logo Element
An image that visually identifies your Atom news feed can be provided by the logo element (Listing 8-43). Its content
is an IRI reference (RFC 3987). The aspect ratio of the logo image should be 2:1 (horizontal to vertical).
Listing 8-43. A Logo Image of an Atom Feed
The published Element
The time when the first version of a news entry was written can be specified by a date construct of the published
element (Listing 8-44).
Listing 8-44. A published Element
Such timestamps might coincide with the content of the updated element in the entry.
The rights Element
Custom copyright information can be written as a text construct and added to your Atom news feed using the rights
element (Listing 8-45).
2 One of the most well-known examples for percent encoding is the %20 string that appears in place of space characters in poorly
3 If percent encoding is essential and cannot be eliminated, letters should be uppercase characters A - F .