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Versions: 00 01 02 03 04 05 06 07 08                                    
Network Working Group                                           J. Snell
Internet-Draft                                            September 2006
Expires: March 5, 2007


                      Atom Bidirectional Attribute
                    draft-snell-atompub-bidi-01.txt

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   This Internet-Draft will expire on March 5, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document updates the Atom Syndication Format by adding a new
   attribute that may be used to indicate the base directionality of
   directionally-neutral characters.









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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Namespace . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.2.  Notational Conventions  . . . . . . . . . . . . . . . . . . 3
   2.  The "dir" Attribute . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     5.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     5.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 7
   Intellectual Property and Copyright Statements  . . . . . . . . . . 8





































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1.  Introduction

   This document updates the Atom Syndication Format [RFC4287] by adding
   a new 'dir' attribute that can be used to define the base
   directionality of directionally-neutral characters contained within
   an Atom document.

1.1.  Namespace

   The XML Namespaces URI [W3C.REC-xml-names-19990114] for the Atom
   Syndication Format is:
   http://www.w3.org/2005/Atom

1.2.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in BCP 14, [RFC2119].

   The Atom Syndication Format [RFC4287] is specified using terms from
   the XML Infoset [W3C.REC-xml-infoset-20040204].  This specification
   uses a shorthand form for two commons terms: The phrase "Information
   Item" is omitted when naming Element and Attribute Information Items.
   Therefore, when this specification uses the term "element," it is
   referring to an Element Information Item in Infoset terms.  Likewise,
   when it uses the term "attribute," it is referring to an Attribute
   Information Item.

   Portions this specification are illustrated with fragments of a non-
   normative RELAX NG Compact schema [RELAXNG].  However, the text of
   this specification provides the sole definition of conformance.


2.  The "dir" Attribute

   The "dir" attribute 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, "lro" and "rlo" indicating explicit "left-to-right" and
   "right-to-left" overrides, or an empty string indicating that no
   base-direction is specified.  If the "dir" attribute is not
   specified, the value is assumed to be an empty string.  The attribute
   can appear anywhere in an Atom document, except where it is
   explicitly forbidden.







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

   The direction specified by "dir" applies to elements and attributes
   whose values are specified as being "Language-Sensitive" as defined
   by Section 2 of [RFC4287].  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 [UNI9] MUST be used to render that
   text.  Because consumers of Atom documents vary broadly in the way
   they display text, the "ltr" and "rtl" values do 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.

   The "lro" and "rlo" values override the inherent directionality of
   characters as defined by [UNICODE].  When used, affected text MUST be
   rendered as if preceded by either Unicode character U+202D (left-to-
   right override) or U+202E (right-to-left override) and followed by
   U+202C (pop directional formatting).

   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.  The value of the "dir" attribute does define the
   base directionality of Language-Sensitive text within Text Constructs
   and atom:content elements regardless of the value of the type
   attribute.

   Example atom:feed with bidirectional XHTML:









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     <?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.
   Implementers are reminded that unexpected results could occur when
   using both the "dir" attribute and the Unicode control characters
   within a single document.


3.  Security Considerations

   The security considerations discussed in [RFC4287] Section 8 apply.


4.  IANA Considerations

   No IANA actions are required by this document.


5.  References

5.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4287]  Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
              Syndication Format", RFC 4287, December 2005.

   [UNI9]     Davis, M., "The Bidirectional Algorithm", March 2004.

   [UNICODE]  International Organization for Standardization, "ISO/IEC
              10646:2003: Information Technology - Universal Multiple-
              Octet Coded Character Set (UCS)", December 2003.

   [W3C.REC-xml-infoset-20040204]
              Cowan, J. and R. Tobin, "XML Information Set (Second
              Edition)", World Wide Web Consortium Recommendation REC-
              xml-infoset-20040204, February 2004,
              <http://www.w3.org/TR/2004/REC-xml-infoset-20040204>.



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   [W3C.REC-xml-names-19990114]
              Layman, A., Bray, T., and D. Hollander, "Namespaces in
              XML", World Wide Web Consortium Recommendation REC-xml-
              names-19990114, January 1999,
              <http://www.w3.org/TR/1999/REC-xml-names-19990114>.

5.2.  Informative References

   [RELAXNG]  Clark, J., "RELAX NG Compact Syntax", December 2001, <http
              ://www.oasis-open.org/committees/relax-ng/
              compact-20021121.html>.


Appendix A.  Acknowledgements

   TBD



































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Author's Address

   James M Snell

   Email: jasnell@gmail.com
   URI:   http://www.snellspace.com













































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   Internet Society.




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