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'ABNF') (Obsoleted by RFC 5234) == Outdated reference: draft-daboo-imap-annotatemore has been published as RFC 5464 ** Obsolete normative reference: RFC 3501 (Obsoleted by RFC 9051) Summary: 3 errors (**), 0 flaws (~~), 4 warnings (==), 8 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Melnikov 3 Internet-Draft Isode Ltd 4 Intended status: Standards Track P. Coates 5 Expires: July 27, 2008 Sun Microsystems 6 January 24, 2008 8 Discovery of CONVERT parameters 9 draft-melnikov-lemonade-convert-discovery-00.txt 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on July 27, 2008. 36 Copyright Notice 38 Copyright (C) The IETF Trust (2008). 40 Abstract 42 This is a companion document to the Lemonade CONVERT 43 (draft-ietf-lemonade-convert-XX.txt) extension. It summarizes 44 various proposals for CONVERT MIME type and conversion parameter 45 discovery. 47 Table of Contents 49 1. Requirements notation . . . . . . . . . . . . . . . . . . . . . 3 50 2. Discovery of available conversions and controlling default 51 conversions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 2.1. Client preferences regarding default conversions: 53 MEDIACAPS Command . . . . . . . . . . . . . . . . . . . . . 3 54 2.2. Discovery of available conversions . . . . . . . . . . . . 4 55 2.2.1. GETMETADATA . . . . . . . . . . . . . . . . . . . . . . 4 56 2.2.2. CONVERSIONS command . . . . . . . . . . . . . . . . . . 6 57 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 58 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 59 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7 60 6. Normative References . . . . . . . . . . . . . . . . . . . . . 8 61 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 62 Intellectual Property and Copyright Statements . . . . . . . . . . 9 64 1. Requirements notation 66 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 67 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 68 document are to be interpreted as described in [RFC2119]. 70 In examples, "C:" and "S:" indicate lines sent by the client and 71 server respectively. If a single "C:" or "S:" label applies to 72 multiple lines, then the line breaks between those lines are for 73 editorial clarity only and are not part of the actual protocol 74 exchange. The five characters [...] means that something has been 75 elided. 77 [[anchor2: Editorial comments and questions are marked like this.]] 79 2. Discovery of available conversions and controlling default 80 conversions 82 2.1. Client preferences regarding default conversions: MEDIACAPS 83 Command 85 Arguments: list of supported MIME types and corresponding conversion 86 parameters 88 Responses: none 90 Result: OK - MEDIACAPS command completed 91 BAD - unrecognized syntax of an argument 93 The client list MIME types and corresponding conversion parameters in 94 the order of preference, starting with the most prefered MIME media 95 type(s). 97 Servers MUST ignore conversion parameters and MIME types that they 98 don't recognize. 100 If a MEDIACAPS command was issued on a connection and the client has 101 requested to perform the default conversion (see section 5 for more 102 details), the server MUST use one of the MIME types specified by the 103 client in this command as the target MIME type. The server SHOULD 104 use the first MIME type from the ordered list that it supports. 106 Example: 108 C: A01 MEDIACAPS ("TEXT" "HTML") ("TEXT" "PLAIN" "FORMAT" ("FLOWED" 109 "FIXED")) ("TEXT" "*" "CHARSET" ("UTF-8" "US-ASCII")) ("IMAGE" 110 ("JPEG" "PNG" "GIF") "PIX-X" "240" "PIX-Y" "320") 112 [[anchor5: The FORMAT conversion parameter is not registered with 113 IANA]] 115 With such command the client is saying (each parenthesized list 116 converted to a sentence): "I do text/html. I will also do text/ 117 plain, preferably with format=flowed, but I can handle format=fixed 118 too. For all text media types I do, I can handle a charset of either 119 UTF-8 or US-ASCII. I can handle image/jpeg, image/png, and, least 120 preferred, image/gif, and my ideal resolution is 240x320." 122 ABNF for this command is as follows: 124 mediacaps-cmd = "MEDIACAPS" 1*(SP mediacap) 126 mediacap = "(" media-type SP media-subtype 127 *( SP media-param SP media-param-values ) ")" 129 media-type = astring 131 media-subtype = DQUOTE "*" DQUOTE / 132 astring / 133 "(" astring *( SP astring ) ")" 134 ;; "*" means all subtypes for the media-type specified 135 ;; in the command. 136 ;; Otherwise, either the specific subtype or a list of them. 138 media-param = astring 140 media-param-values = astring / "(" astring *(SP astring) ")" 141 ;; Either a single acceptable value or a list of 142 ;; acceptable values. 144 2.2. Discovery of available conversions 146 [[anchor7: Note that only one of the proposals specified in 147 subsections of this section will be standardized.]] 149 2.2.1. GETMETADATA 151 [[anchor9: Proposal # 1]] 153 To determine which conversions are supported, server annotations are 154 used. For each MIME format (/ [MIME-IMT]) that can be 155 converted, an annotation with the name "/convert/// 156 types" SHOULD exist. The "value.shared" attribute of this annotation 157 contains a semicolon separated list of type/subtype output formats. 159 The selection of available conversions MAY be adjustable by the 160 server administrator, and MAY be sensitive to the current user. The 161 selection of available conversions MAY also depend on information 162 about the client obtained through a different mechanism outside the 163 scope of CONVERT (e.g. dynamically through device description 164 mechanisms or when the device was associated to the account). 166 For each source MIME type that the client is interested in, it SHOULD 167 determine which target conversions are supported by reading the 168 "value.shared" attribute. 170 In addition to the subtype-specific annotations, a special "wildcard" 171 annotation named "/convert//@/types" MAY be used to reference 172 any subtype of media type. A client that doesn't find an 173 "/convert///types" annotation SHOULD check the value 174 of the "/convert//@/types" annotation. 176 Note that names of server annotations are case-sensitive (see 177 [METADATA]). In order to guaranty interoperability, clients and 178 servers MUST use the lowercased version of and when 179 constructing an annotation name described above. 181 Example: Discover all image conversions 183 C: a GETMETADATA "/convert/image/@/types" value.shared 184 S: * METADATA "/convert/image/@/types" 185 (value.shared "image/jpeg;image/png;image/gif") 186 S: a OK GETMETADATA complete 188 The above example shows that the server supports one kind of input 189 image transcoding, from image/jpeg to three different outputs: JPEG, 190 PNG, and GIF. 192 For a given conversion, optional transcoding parameters MAY be 193 present. These are mapped into the "value.shared" attribute in the 194 "/convert/////params" 195 annotation. A client wishing to use a conversion parameter SHOULD 196 check if the server will accept it by reading the "value.shared" 197 attribute. 199 Example: Discover optional parameters for image/jpeg -> image/gif. 201 C: a GETMETADATA /convert/image/jpeg/image/gif/params 202 "value.shared" 203 S: * METADATA /convert/image/jpeg/image/gif/params 204 ("value.shared" "pix-x;pix-y") 205 S: a OK GETMETADATA complete 207 The above example shows that to convert from image/jpeg to image/gif, 208 the transcoding supports the following types of optional parameters: 209 pix-x (width), pix-y (height). 211 As with conversion types, some "wildcarding" is permitted. Thus if 212 the same parameters are allowed for all conversions to image/gif, 213 then the server can store the one metadata value "/convert/@/@/image/ 214 gif/parameters". 216 A client MAY use these values to check whether or not a desired 217 conversion is possible, or it might, for example, present the 218 parameters as a GUI preferences pane for the user to customize. 220 If the client is going to check which conversion parameters are 221 available, it MUST read the "value.shared" attribute from the 222 following annotations in the following order: 224 "/convert/////params" 225 "/convert//@///params" 226 "/convert/@/@///params" 228 The client MUST use the "value.shared" attribute value from the first 229 existing annotation in the list specified above. 231 2.2.2. CONVERSIONS command 233 [[anchor11: Proposal # 2]] 235 Arguments: source MIME type 236 target MIME type 238 Responses: untagged responses: CONVERSION 240 Result: OK - CONVERSIONS command completed 241 BAD - unrecognized syntax of an argument, 242 unexpected extra argument, missing argument, etc. 244 The first parameter to the CONVERSIONS command is a source MIME type, 245 the second parameter is the target MIME type. Both parameters are 246 partially (e.g. "text/*") or completely ("*") wildcardable. 248 Conversions matching the source/target pair and their associated 249 conversion parameters are returned in untagged CONVERSIONS responses. 250 If source/target doesn't match any conversion supported by the 251 server, no CONVERSIONS response is returned. 253 Examples: 255 For conversion info from GIF to JPEG (no untagged CONVERT would be 256 returned if no conversion was possible): 258 C: a CONVERSIONS "image/gif" "image/jpeg" 259 S: * CONVERSION "image/gif" "image/jpeg" ("width" "height" 260 "depth" "interlaced") 261 S: a OK CONVERSIONS completed 263 For conversion info from GIF to anything: 265 C: b CONVERSIONS "image/gif" * 266 S: * CONVERSION "image/gif" "image/jpeg" ("width" "height" 267 "depth" "interlaced") 268 S: * CONVERSION "image/gif" "image/png" (...) 269 [...] 270 S: b OK CONVERSIONS completed 272 For conversion of anything to JPEG: 274 C: c CONVERSIONS * "image/jpeg" 275 S: * CONVERSION "image/gif" "image/jpeg" ("width" "height" 276 "depth" "interlaced") 277 S: * CONVERSION "image/png" "image/jpeg" (...) 278 [...] 279 S: c OK CONVERSIONS completed 281 For conversions from all image formats to all text formats (maybe via 282 OCR?): 284 C: d CONVERSIONS "image/*" "text/*" 285 S: d OK CONVERSIONS completed 287 [[anchor12: ABNF is missing for this proposal.]] 289 3. IANA Considerations 291 TBD if needed. 293 4. Security Considerations 295 [[anchor15: TBD]] 297 5. Acknowledgments 299 Authors would also like to thank Dave Cridland for the MEDIACAPS 300 command proposal and Dan Karp for the CONVERSIONS command proposal. 302 6. Normative References 304 [ABNF] Crocker, D., Ed. and P. Overell, Ed., "Augmented BNF for 305 Syntax Specifications: ABNF", RFC 4234, October 2005. 307 [METADATA] 308 Daboo, C., "IMAP METADATA Extension", 309 draft-daboo-imap-annotatemore (work in progress), 310 December 2007. 312 [MIME-IMT] 313 Freed, N. and N. Borenstein, "MIME (Multipurpose Internet 314 Mail Extensions) Part Two: Media Types", RFC 2046, 315 November 1996. 317 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 318 Requirement Levels", BCP 14, RFC 2119, March 1997. 320 [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 321 4rev1", RFC 3501, March 2003. 323 Authors' Addresses 325 Alexey Melnikov 326 Isode Ltd 327 5 Castle Business Village 328 36 Station Road 329 Hampton, Middlesex TW12 2BX 330 UK 332 Email: Alexey.Melnikov@isode.com 334 Peter Coates 335 Sun Microsystems 336 185 Falcon Drive 337 Whitehorse, YT Y1A 6T2 338 Canada 340 Email: peter.coates@Sun.COM 342 Full Copyright Statement 344 Copyright (C) The IETF Trust (2008). 346 This document is subject to the rights, licenses and restrictions 347 contained in BCP 78, and except as set forth therein, the authors 348 retain all their rights. 350 This document and the information contained herein are provided on an 351 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 352 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 353 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 354 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 355 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 356 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 358 Intellectual Property 360 The IETF takes no position regarding the validity or scope of any 361 Intellectual Property Rights or other rights that might be claimed to 362 pertain to the implementation or use of the technology described in 363 this document or the extent to which any license under such rights 364 might or might not be available; nor does it represent that it has 365 made any independent effort to identify any such rights. 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