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(See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (September 2006) is 6427 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'UNI9' -- Possible downref: Non-RFC (?) normative reference: ref. 'UNICODE' Summary: 3 errors (**), 0 flaws (~~), 2 warnings (==), 9 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Snell 3 Internet-Draft September 2006 4 Expires: March 5, 2007 6 Atom Bidirectional Extension 7 draft-snell-atompub-bidi-00.txt 9 Status of this Memo 11 By submitting this Internet-Draft, each author represents that any 12 applicable patent or other IPR claims of which he or she is aware 13 have been or will be disclosed, and any of which he or she becomes 14 aware will be disclosed, in accordance with Section 6 of BCP 79. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on March 5, 2007. 34 Copyright Notice 36 Copyright (C) The Internet Society (2006). 38 Abstract 40 This document describes an extension to the Atom format that can be 41 used to define the base directionality of directionally-neutral 42 characters contained within an Atom document. 44 Table of Contents 46 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 47 1.1. Namespace . . . . . . . . . . . . . . . . . . . . . . . . . 3 48 1.2. Notational Conventions . . . . . . . . . . . . . . . . . . 3 49 2. The "u:dir" Attribute . . . . . . . . . . . . . . . . . . . . . 3 50 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 51 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 52 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 53 5.1. Normative References . . . . . . . . . . . . . . . . . . . 5 54 5.2. Informative References . . . . . . . . . . . . . . . . . . 6 55 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 6 56 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 57 Intellectual Property and Copyright Statements . . . . . . . . . . 8 59 1. Introduction 61 This document describes an extension to the Atom format [RFC4287] 62 that can be used to define the base directionality of directionally- 63 neutral characters contained within an Atom document. 65 1.1. Namespace 67 The XML Namespaces URI [W3C.REC-xml-names-19990114] for the XML 68 elements and attributes described in this specification is 69 http://purl.org/atompub/bidi 71 In this document, the namespace prefix "u:" is used for the above 72 Namespace URI. Note that the choice of namespace prefix is arbitrary 73 and not semantically significant. 75 1.2. Notational Conventions 77 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 78 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 79 document are to be interpreted as described in BCP 14, [RFC2119]. 81 This extension is, like the Atom Syndication Format [RFC4287] itself, 82 specified using terms from the XML Infoset [W3C.REC-xml-infoset- 83 20040204]. However, this specification uses a shorthand form for two 84 commons terms: The phrase "Information Item" is omitted when naming 85 Element and Attribute Information Items. Therefore, when this 86 specification uses the term "element," it is referring to an Element 87 Information Item in Infoset terms. Likewise, when it uses the term 88 "attribute," it is referring to an Attribute Information Item. 90 Some sections of this specification are illustrated with fragments of 91 a non-normative RELAX NG Compact schema [RELAXNG]. However, the text 92 of this specification provides the sole definition of conformance. 94 2. The "u:dir" Attribute 96 The "u:dir" attribute specifies the base direction of directionally- 97 neutral text [UNICODE]. Possible values for the attribute are "ltr" 98 and "rtl" indicating "left-to-right" and "right-to-left" 99 respectively, "lro" and "rlo" indicating explicit "left-to-right" and 100 "right-to-left" overrides, or an empty string indicating that no 101 base-direction is specified. If the "u:dir" attribute is not 102 specified, the value is assumed to be an empty string. The attribute 103 can appear anywhere in an Atom document, except where it is 104 explicitly forbidden. 106 dir = attribute u:dir { "ltr" | "rtl" | "lro" | "rlo" | "" } 108 The direction specified by "u:dir" applies only to elements and 109 attributes whose values are specified as being "Language-Sensitive" 110 as defined by Section 2 of [RFC4287]. The attribute is inherited by 111 descendent elements and may be overridden. 113 Example atom:feed with right-to-left directionality 115 116 118 ٹٺٻ 119 ... 120 122 If an Atom document contains any right-to-left characters, the 123 Unicode Bidirectional Algorithm [UNI9] MUST be used to render that 124 text. Because consumers of Atom documents vary broadly in the way 125 they display text, the "ltr" and "rtl" values do not necessarily open 126 an additional level of embedding with respect to the bidirectional 127 algorithm. Consuming applications that render bidirectional text are 128 responsible for determining the appropriate level of embedding. 130 The "lro" and "rlo" values override the inherent directionality of 131 characters as defined by [UNICODE]. When used, affected text MUST be 132 rendered as if preceded by either Unicode character U+202D (left-to- 133 right override) or U+202E (right-to-left override) and followed by 134 U+202C (pop directional formatting). 136 When Atom Text Constructs or the atom:content elements contain 137 bidirectional text and the type attribute is set to either "html" or 138 "xhtml", the bidirectional markup mechanisms specific to each format 139 SHOULD be used. The value of the "u:dir" attribute does define the 140 base directionality of Language-Sensitive text within Text Constructs 141 and atom:content elements regardless of the value of the type 142 attribute. 144 Example atom:feed with bidirectional XHTML: 146 147 149 150 <div xmlns="http://www.w3.org/1999/xhtml"> 151 <p dir="rtl">ٹٺٻ</p> 152 </div> 153 154 ... 155 157 The Unicode bidirectional control characters MAY also be used within 158 attributes and element values to indicate the directionality of text. 159 Implementers are reminded that unexpected results could occur when 160 using both the "u:dir" attribute and the Unicode control characters 161 within a single document. 163 3. Security Considerations 165 The security considerations discussed in [RFC4287] Section 8 apply. 167 4. IANA Considerations 169 No IANA actions are required by this document. 171 5. References 173 5.1. Normative References 175 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 176 Requirement Levels", BCP 14, RFC 2119, March 1997. 178 [RFC4287] Nottingham, M., Ed. and R. Sayre, Ed., "The Atom 179 Syndication Format", RFC 4287, December 2005. 181 [UNI9] Davis, M., "The Bidirectional Algorithm", March 2004. 183 [UNICODE] International Organization for Standardization, "ISO/IEC 184 10646:2003: Information Technology - Universal Multiple- 185 Octet Coded Character Set (UCS)", December 2003. 187 [W3C.REC-xml-infoset-20040204] 188 Cowan, J. and R. Tobin, "XML Information Set (Second 189 Edition)", World Wide Web Consortium Recommendation REC- 190 xml-infoset-20040204, February 2004, 191 . 193 [W3C.REC-xml-names-19990114] 194 Layman, A., Bray, T., and D. Hollander, "Namespaces in 195 XML", World Wide Web Consortium Recommendation REC-xml- 196 names-19990114, January 1999, 197 . 199 5.2. Informative References 201 [RELAXNG] Clark, J., "RELAX NG Compact Syntax", December 2001, . 205 Appendix A. Acknowledgements 207 TBD 209 Author's Address 211 James M Snell 213 Email: jasnell@gmail.com 214 URI: http://www.snellspace.com 216 Intellectual Property Statement 218 The IETF takes no position regarding the validity or scope of any 219 Intellectual Property Rights or other rights that might be claimed to 220 pertain to the implementation or use of the technology described in 221 this document or the extent to which any license under such rights 222 might or might not be available; nor does it represent that it has 223 made any independent effort to identify any such rights. Information 224 on the procedures with respect to rights in RFC documents can be 225 found in BCP 78 and BCP 79. 227 Copies of IPR disclosures made to the IETF Secretariat and any 228 assurances of licenses to be made available, or the result of an 229 attempt made to obtain a general license or permission for the use of 230 such proprietary rights by implementers or users of this 231 specification can be obtained from the IETF on-line IPR repository at 232 http://www.ietf.org/ipr. 234 The IETF invites any interested party to bring to its attention any 235 copyrights, patents or patent applications, or other proprietary 236 rights that may cover technology that may be required to implement 237 this standard. Please address the information to the IETF at 238 ietf-ipr@ietf.org. 240 Disclaimer of Validity 242 This document and the information contained herein are provided on an 243 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 244 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 245 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 246 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE 247 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 248 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 250 Copyright Statement 252 Copyright (C) The Internet Society (2006). This document is subject 253 to the rights, licenses and restrictions contained in BCP 78, and 254 except as set forth therein, the authors retain all their rights. 256 Acknowledgment 258 Funding for the RFC Editor function is currently provided by the 259 Internet Society.