PaceAtomBidi

[James M Snell]

This ought to give us something concrete to work from.

- James

#pragma section-numbers off

== Abstract ==

RFC4287 currently has no *efficient* means of indicating the base
directionality of text.  While the Unicode bidi control characters can
be used, they can be problematic to use correctly within XML and do not
allow publishers to set a single default direction for a complete Atom
document.

This proposal adds a new common attribute to all Atom elements called
"dir".  The attribute is optional and has three possible values, "ltr",
"rtl" and "" (representing 'unspecified').  If the attribute is missing,
the value is considered to be unspecified.  This should make the element
fully backwards compatible with existing compliant RFC4287
implementations that properly handle "unknown markup".

This proposal does add the requirement that bidi text in atom docs MUST
be rendered using the unicode bidi algorithm but makes it clear that the
use of dir on an element does not necessarily open a new level of
embedding... meaning that feed consumers have the responsibility of
determining how to apply the bidi algorithm based on how those consumers
choose to display the text (e.g. some readers may display entry content
in a <div> while others may display content in a <span>, both of which
handle bidi text differently depending on context).

I also specify that bidi text in (x)html should use the bidi markup as
defined by those specs.

== Status ==

Proposed.

== Rationale ==

(see abstract)

== Proposal ==

{{{

2.0 Add "dir" to atomCommonAttributes

   atomCommonAttributes =
      attribute xml:base { atomUri }?,
      attribute xml:lang { atomLanguageTag }?,
      attribute dir { "ltr" | "rtl" | "" }?,
      undefinedAttribute*

2.1 The "dir" Attribute

Any element defined by this specification MAY have a "dir" attribute
whose content specifies the base direction of directionally-neutral text
[UNICODE].  Possible values for the attribute are "ltr" and "rtl"
indicating "left-to-right" and "right-to-left" respectively or an empty
string "" indicating that no base-direction is unspecified.  If the"dir"
attribute is not specified, the value is assumed to be unspecified.

The direction specified by "dir" applies only to elements and attributes
whose values are specified as being "Language-Sensitive".  The attribute
is inherited by descendent elements and may be overridden.

Example atom:feed with right-to-left directionality

  <?xml version="1.0" ?>
  <feed xmlns="http://www.w3.org/2005/Atom"; dir="rtl">
    <title>&#x0679&#x067A;&#x067B;</title>
    ...
  </feed>

If an Atom document contains any right-to-left characters, the Unicode
Bidirectional Algorithm [UAX#9] MUST be used to render that text.
Because consumers of Atom documents vary broadly in the way they display
text, the use of the "dir" attribute on an element does not necessarily
open an additional level of embedding with respect to the bidirectional
algorithm. Consuming applications that render bidirectional text are
responsible for determining the appropriate level of embedding.

When Atom Text Constructs or the atom:content elements contain
bidirectional text and the type attribute is set to either "html" or
"xhtml", the bidirectional markup mechanisms specific to each format
SHOULD be used.

Example atom:feed with bidirectional XHTML

  <?xml version="1.0" ?>
  <feed xmlns="http://www.w3.org/2005/Atom"; dir="rtl">
    <title type="xhtml">
      <div xmlns="http://www.w3.org/1999/xhtml";>
        <p dir="rtl">&#x0679&#x067A;&#x067B;</p>
      </div>
    </title>
    ...
  </feed>

The Unicode bidirectional control characters MAY also be used within
attributes and element values to indicate the directionality of text.

IRI's containing bidirectional characters MUST be stored, transmitted
and rendered as defined in [RFC3987] Section 4.
}}}

== Impacts ==



== Notes ==


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CategoryProposals