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| 6 | + |
| 7 | +Network Working Group A. Melnikov |
| 8 | +Request for Comments: 5182 Isode Ltd. |
| 9 | +Updates: 3501 March 2008 |
| 10 | +Category: Standards Track |
| 11 | + |
| 12 | + |
| 13 | + IMAP Extension for Referencing the Last SEARCH Result |
| 14 | + |
| 15 | +Status of This Memo |
| 16 | + |
| 17 | + This document specifies an Internet standards track protocol for the |
| 18 | + Internet community, and requests discussion and suggestions for |
| 19 | + improvements. Please refer to the current edition of the "Internet |
| 20 | + Official Protocol Standards" (STD 1) for the standardization state |
| 21 | + and status of this protocol. Distribution of this memo is unlimited. |
| 22 | + |
| 23 | +Abstract |
| 24 | + |
| 25 | + Many IMAP clients use the result of a SEARCH command as the input to |
| 26 | + perform another operation, for example, fetching the found messages, |
| 27 | + deleting them, or copying them to another mailbox. |
| 28 | + |
| 29 | + This can be achieved using standard IMAP operations described in RFC |
| 30 | + 3501; however, this would be suboptimal. The server will send the |
| 31 | + list of found messages to the client; after that, the client will |
| 32 | + have to parse the list, reformat it, and send it back to the server. |
| 33 | + The client can't pipeline the SEARCH command with the subsequent |
| 34 | + command, and, as a result, the server might not be able to perform |
| 35 | + some optimizations. |
| 36 | + |
| 37 | + This document proposes an IMAP extension that allows a client to tell |
| 38 | + a server to use the result of a SEARCH (or Unique Identifier (UID) |
| 39 | + SEARCH) command as an input to any subsequent command. |
| 40 | + |
| 41 | +1. Introduction |
| 42 | + |
| 43 | + Many IMAP clients use the result of a SEARCH command as the input to |
| 44 | + perform another operation, for example, fetching the found messages, |
| 45 | + deleting them, or copying them to another mailbox. |
| 46 | + |
| 47 | + This document proposes an IMAP extension that allows a client to tell |
| 48 | + a server to use the result of a SEARCH (or UID SEARCH) command as an |
| 49 | + input to any subsequent command. |
| 50 | + |
| 51 | + The SEARCH result reference extension defines a new SEARCH result |
| 52 | + option [IMAPABNF] "SAVE" that tells the server to remember the result |
| 53 | + of the SEARCH or UID SEARCH command (as well as any command based on |
| 54 | + SEARCH, e.g., SORT and THREAD [SORT]) and store it in an internal |
| 55 | + |
| 56 | + |
| 57 | + |
| 58 | +Melnikov Standards Track [Page 1] |
| 59 | + |
| 60 | +RFC 5182 Last SEARCH Result Reference March 2008 |
| 61 | + |
| 62 | + |
| 63 | + variable that we will reference as the "search result variable". The |
| 64 | + client can use the "$" marker to reference the content of this |
| 65 | + internal variable. The "$" marker can be used instead of message |
| 66 | + sequence or UID sequence in order to indicate that the server should |
| 67 | + substitute it with the list of messages from the search result |
| 68 | + variable. Thus, the client can use the result of the latest |
| 69 | + remembered SEARCH command as a parameter to another command. The |
| 70 | + search result marker has several advantages: |
| 71 | + |
| 72 | + * it avoids wasted bandwidth and associated delay; |
| 73 | + |
| 74 | + * it allows the client to pipeline a SEARCH [IMAP4] command with a |
| 75 | + subsequent FETCH/STORE/COPY/SEARCH [IMAP4] or UID EXPUNGE |
| 76 | + [UIDPLUS] command; |
| 77 | + |
| 78 | + * the client doesn't need to spend time reformatting the result of |
| 79 | + a SEARCH command into a message set used in the subsequent |
| 80 | + command; |
| 81 | + |
| 82 | + * it allows the server to perform optimizations. For example, if |
| 83 | + the server can execute several pipelined commands in parallel |
| 84 | + (or out of order), presence of the search result marker can |
| 85 | + allow the server to decide which commands may or may not be |
| 86 | + executed out of order. |
| 87 | + |
| 88 | + In absence of any other SEARCH result option, the SAVE result option |
| 89 | + also suppresses any SEARCH response that would have been otherwise |
| 90 | + returned by the SEARCH command. |
| 91 | + |
| 92 | +1.1. Conventions Used in This Document |
| 93 | + |
| 94 | + In examples, "C:" indicates lines sent by a client that is connected |
| 95 | + to a server. "S:" indicates lines sent by the server to the client. |
| 96 | + |
| 97 | + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", |
| 98 | + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this |
| 99 | + document are to be interpreted as described in [KEYWORDS]. |
| 100 | + |
| 101 | + Explanatory comments in examples start with // and are not part of |
| 102 | + the protocol. |
| 103 | + |
| 104 | + |
| 105 | + |
| 106 | + |
| 107 | + |
| 108 | + |
| 109 | + |
| 110 | + |
| 111 | + |
| 112 | + |
| 113 | + |
| 114 | +Melnikov Standards Track [Page 2] |
| 115 | + |
| 116 | +RFC 5182 Last SEARCH Result Reference March 2008 |
| 117 | + |
| 118 | + |
| 119 | +2. Overview |
| 120 | + |
| 121 | +2.1. Normative Description of the SEARCHRES Extension |
| 122 | + |
| 123 | + The SEARCH result reference extension described in this document is |
| 124 | + present in any IMAP4 server implementation that returns "SEARCHRES" |
| 125 | + as one of the supported capabilities in the CAPABILITY command |
| 126 | + response. Any such server MUST also implement the [ESEARCH] |
| 127 | + extension. |
| 128 | + |
| 129 | + Upon successful completion of a SELECT or an EXAMINE command (after |
| 130 | + the tagged OK response), the current search result variable is reset |
| 131 | + to the empty sequence. |
| 132 | + |
| 133 | + A successful SEARCH command with the SAVE result option sets the |
| 134 | + value of the search result variable to the list of messages found in |
| 135 | + the SEARCH command. For example, if no messages were found, the |
| 136 | + search result variable will contain the empty list. |
| 137 | + |
| 138 | + Any of the following SEARCH commands MUST NOT change the search |
| 139 | + result variable: |
| 140 | + |
| 141 | + o a SEARCH command that caused the server to return the BAD tagged |
| 142 | + response, |
| 143 | + |
| 144 | + o a SEARCH command with no SAVE result option that caused the |
| 145 | + server to return NO tagged response, |
| 146 | + |
| 147 | + o a successful SEARCH command with no SAVE result option. |
| 148 | + |
| 149 | + A SEARCH command with the SAVE result option that caused the server |
| 150 | + to return the NO tagged response sets the value of the search result |
| 151 | + variable to the empty sequence. |
| 152 | + |
| 153 | + When a message listed in the search result variable is EXPUNGEd, it |
| 154 | + is automatically removed from the list. Implementors are reminded |
| 155 | + that if the server stores the list as a list of message numbers, it |
| 156 | + MUST automatically adjust them when notifying the client about |
| 157 | + expunged messages, as described in Section 7.4.1 of [IMAP4]. |
| 158 | + |
| 159 | + If the server decides to send a new UIDVALIDITY value while the |
| 160 | + mailbox is opened, this causes resetting of the search variable to |
| 161 | + the empty list. |
| 162 | + |
| 163 | + |
| 164 | + |
| 165 | + |
| 166 | + |
| 167 | + |
| 168 | + |
| 169 | + |
| 170 | +Melnikov Standards Track [Page 3] |
| 171 | + |
| 172 | +RFC 5182 Last SEARCH Result Reference March 2008 |
| 173 | + |
| 174 | + |
| 175 | + Note that even if the "$" marker contains the empty list of messages, |
| 176 | + it must be treated by all commands accepting message sets as |
| 177 | + parameters as a valid, but non-matching list of messages. For |
| 178 | + example, the "FETCH $" command would return a tagged OK response and |
| 179 | + no FETCH responses. See also the Example 5 below. |
| 180 | + |
| 181 | + Note that even if the "$" marker contains the empty list of messages, |
| 182 | + it must be treated as a valid but non-matching list of messages, by |
| 183 | + all commands that accept message sets as parameters. |
| 184 | + |
| 185 | + Implementation note: server implementors should note that "$" can |
| 186 | + reference IMAP message sequences or UID sequences, depending on the |
| 187 | + context where it is used. For example, the "$" marker can be set as |
| 188 | + a result of a SEARCH (SAVE) command and used as a parameter to a UID |
| 189 | + FETCH command (which accepts a UID sequence, not a message sequence), |
| 190 | + or the "$" marker can be set as a result of a UID SEARCH (SAVE) |
| 191 | + command and used as a parameter to a FETCH command (which accepts a |
| 192 | + message sequence, not a UID sequence). |
| 193 | + |
| 194 | +2.2. Examples |
| 195 | + |
| 196 | + 1) The following example demonstrates how the client can use the |
| 197 | + result of a SEARCH command to FETCH headers of interesting |
| 198 | + messages: |
| 199 | + |
| 200 | + Example 1: |
| 201 | + C: A282 SEARCH RETURN (SAVE) FLAGGED SINCE 1-Feb-1994 |
| 202 | + NOT FROM "Smith" |
| 203 | + S: A282 OK SEARCH completed, result saved |
| 204 | + C: A283 FETCH $ (UID INTERNALDATE FLAGS RFC822.HEADER) |
| 205 | + S: * 2 FETCH (UID 14 ... |
| 206 | + S: * 84 FETCH (UID 100 ... |
| 207 | + S: * 882 FETCH (UID 1115 ... |
| 208 | + S: A283 OK completed |
| 209 | + |
| 210 | + The client can also pipeline the two commands: |
| 211 | + |
| 212 | + Example 2: |
| 213 | + C: A282 SEARCH RETURN (SAVE) FLAGGED SINCE 1-Feb-1994 |
| 214 | + NOT FROM "Smith" |
| 215 | + C: A283 FETCH $ (UID INTERNALDATE FLAGS RFC822.HEADER) |
| 216 | + S: A282 OK SEARCH completed |
| 217 | + S: * 2 FETCH (UID 14 ... |
| 218 | + S: * 84 FETCH (UID 100 ... |
| 219 | + S: * 882 FETCH (UID 1115 ... |
| 220 | + S: A283 OK completed |
| 221 | + |
| 222 | + |
| 223 | + |
| 224 | + |
| 225 | + |
| 226 | +Melnikov Standards Track [Page 4] |
| 227 | + |
| 228 | +RFC 5182 Last SEARCH Result Reference March 2008 |
| 229 | + |
| 230 | + |
| 231 | + 2) The following example demonstrates that the result of one SEARCH |
| 232 | + command can be used as input to another SEARCH command: |
| 233 | + |
| 234 | + Example 3: |
| 235 | + C: A300 SEARCH RETURN (SAVE) SINCE 1-Jan-2004 |
| 236 | + NOT FROM "Smith" |
| 237 | + S: A300 OK SEARCH completed |
| 238 | + C: A301 UID SEARCH UID $ SMALLER 4096 |
| 239 | + S: * SEARCH 17 900 901 |
| 240 | + S: A301 OK completed |
| 241 | + |
| 242 | + Note that the second command in Example 3 can be replaced with: |
| 243 | + C: A301 UID SEARCH $ SMALLER 4096 |
| 244 | + and the result of the command would be the same. |
| 245 | + |
| 246 | + 3) The following example shows that the "$" |
| 247 | + marker can be combined with other message numbers using the OR |
| 248 | + SEARCH criterion. |
| 249 | + |
| 250 | + Example 4: |
| 251 | + C: P282 SEARCH RETURN (SAVE) SINCE 1-Feb-1994 |
| 252 | + NOT FROM "Smith" |
| 253 | + S: P282 OK SEARCH completed |
| 254 | + C: P283 SEARCH CHARSET UTF-8 (OR $ 1,3000:3021) TEXT {8} |
| 255 | + C: YYYYYYYY |
| 256 | + S: * SEARCH 882 1102 3003 3005 3006 |
| 257 | + S: P283 OK completed |
| 258 | + |
| 259 | + Note: Since this document format is restricted to 7-bit ASCII text, |
| 260 | + it is not possible to show actual UTF-8 data. The "YYYYYYYY" is a |
| 261 | + placeholder for what would be 8 octets of 8-bit data in an actual |
| 262 | + transaction. |
| 263 | + |
| 264 | + |
| 265 | + |
| 266 | + |
| 267 | + |
| 268 | + |
| 269 | + |
| 270 | + |
| 271 | + |
| 272 | + |
| 273 | + |
| 274 | + |
| 275 | + |
| 276 | + |
| 277 | + |
| 278 | + |
| 279 | + |
| 280 | + |
| 281 | + |
| 282 | +Melnikov Standards Track [Page 5] |
| 283 | + |
| 284 | +RFC 5182 Last SEARCH Result Reference March 2008 |
| 285 | + |
| 286 | + |
| 287 | + 4) The following example demonstrates that a failed SEARCH sets the |
| 288 | + search result variable to the empty list. |
| 289 | + |
| 290 | + Example 5: |
| 291 | + C: B282 SEARCH RETURN (SAVE) SINCE 1-Feb-1994 |
| 292 | + NOT FROM "Smith" |
| 293 | + S: B282 OK SEARCH completed |
| 294 | + C: B283 SEARCH CHARSET KOI8-R (OR $ 1,3000:3021) TEXT {4} |
| 295 | + C: XXXX |
| 296 | + S: B283 NO [BADCHARSET UTF-8] KOI8-R is not supported |
| 297 | + //After this command the saved result variable contains |
| 298 | + //no messages. A client that wants to reissue the B283 |
| 299 | + //SEARCH command with another CHARSET would have to reissue |
| 300 | + //the B282 command as well. One possible workaround for |
| 301 | + //this is to include the desired CHARSET parameter |
| 302 | + //in the earliest SEARCH RETURN (SAVE) command in a |
| 303 | + //sequence of related SEARCH commands. |
| 304 | + //A better approach might be to always use CHARSET UTF-8 |
| 305 | + //instead. |
| 306 | + |
| 307 | + Note: Since this document format is restricted to 7-bit ASCII text, |
| 308 | + it is not possible to show actual KOI8-R data. The "XXXX" is a |
| 309 | + placeholder for what would be 4 octets of 8-bit data in an actual |
| 310 | + transaction. |
| 311 | + |
| 312 | + 5) The following example demonstrates that it is not an error to use |
| 313 | + the "$" marker when it contains no messages. |
| 314 | + |
| 315 | + Example 6: |
| 316 | + C: E282 SEARCH RETURN (SAVE) SINCE 28-Oct-2006 |
| 317 | + NOT FROM "Eric" |
| 318 | + C: E283 COPY $ "Other Messages" |
| 319 | + //The "$" contains no messages |
| 320 | + S: E282 OK SEARCH completed |
| 321 | + S: E283 OK COPY completed, nothing copied |
| 322 | + |
| 323 | +2.3. Multiple Commands in Progress |
| 324 | + |
| 325 | + Use of a SEARCH RETURN (SAVE) command followed by a command using the |
| 326 | + "$" marker creates direct dependency between the two commands. As |
| 327 | + directed by Section 5.5 of [IMAP4], a server MUST execute the two |
| 328 | + commands in the order they were received. (A server capable of |
| 329 | + out-of-order execution can in some cases execute the two commands in |
| 330 | + parallel, for example, if a SEARCH RETURN (SAVE) is followed by |
| 331 | + "SEARCH $", the search criteria from the first command can be |
| 332 | + directly substituted into the second command.) |
| 333 | + |
| 334 | + |
| 335 | + |
| 336 | + |
| 337 | + |
| 338 | +Melnikov Standards Track [Page 6] |
| 339 | + |
| 340 | +RFC 5182 Last SEARCH Result Reference March 2008 |
| 341 | + |
| 342 | + |
| 343 | + A client supporting this extension MAY pipeline a SEARCH RETURN |
| 344 | + (SAVE) command with one or more command using the "$" marker, as long |
| 345 | + as this doesn't create an ambiguity, as described in Section 5.5 of |
| 346 | + [IMAP4]. |
| 347 | + |
| 348 | + Example 7: |
| 349 | + C: F282 SEARCH RETURN (SAVE) KEYWORD $Junk |
| 350 | + C: F283 COPY $ "Junk" |
| 351 | + C: F284 STORE $ +FLAGS.Silent (\Deleted) |
| 352 | + S: F282 OK SEARCH completed |
| 353 | + S: F283 OK COPY completed |
| 354 | + S: F284 OK STORE completed |
| 355 | + |
| 356 | + Example 8: |
| 357 | + C: G282 SEARCH RETURN (SAVE) KEYWORD $Junk |
| 358 | + C: G283 SEARCH RETURN (ALL) SINCE 28-Oct-2006 |
| 359 | + FROM "Eric" |
| 360 | + //The server can execute the two SEARCH commands |
| 361 | + //in any order, as they don't have any dependency. |
| 362 | + //Note that the second command is making use of |
| 363 | + //the [ESEARCH] extension. |
| 364 | + S: * ESEARCH (TAG "G283") ALL 3:15,27,29:103 |
| 365 | + S: G283 OK SEARCH completed |
| 366 | + S: G282 OK SEARCH completed |
| 367 | + |
| 368 | + The following example demonstrates that the result of the second |
| 369 | + SEARCH always overrides the result of the first. |
| 370 | + |
| 371 | + Example 9: |
| 372 | + C: H282 SEARCH RETURN (SAVE) KEYWORD $Junk |
| 373 | + C: H283 SEARCH RETURN (SAVE) SINCE 28-Oct-2006 |
| 374 | + FROM "Eric" |
| 375 | + S: H282 OK SEARCH completed |
| 376 | + S: H283 OK SEARCH completed |
| 377 | + |
| 378 | +2.4. Interaction with ESEARCH Extension |
| 379 | + |
| 380 | + Servers that implement the extension defined in this document MUST |
| 381 | + implement [ESEARCH] and conform to additional requirements listed in |
| 382 | + this section. |
| 383 | + |
| 384 | + The SAVE result option doesn't change whether the server would return |
| 385 | + items corresponding to MIN, MAX, ALL, or COUNT [ESEARCH] result |
| 386 | + options. |
| 387 | + |
| 388 | + |
| 389 | + |
| 390 | + |
| 391 | + |
| 392 | + |
| 393 | + |
| 394 | +Melnikov Standards Track [Page 7] |
| 395 | + |
| 396 | +RFC 5182 Last SEARCH Result Reference March 2008 |
| 397 | + |
| 398 | + |
| 399 | + When the SAVE result option is combined with the MIN or MAX [ESEARCH] |
| 400 | + result option, and none of the other ESEARCH result options are |
| 401 | + present, the corresponding MIN/MAX is returned (if the search result |
| 402 | + is not empty), but the "$" marker would contain a single message as |
| 403 | + returned in the MIN/MAX return item. |
| 404 | + |
| 405 | + If the SAVE result option is combined with both MIN and MAX result |
| 406 | + options, and none of the other ESEARCH result options are present, |
| 407 | + the "$" marker would contain one or two messages as returned in the |
| 408 | + MIN/MAX return items. |
| 409 | + |
| 410 | + If the SAVE result option is combined with the ALL and/or COUNT |
| 411 | + result option(s), the "$" marker would always contain all messages |
| 412 | + found by the SEARCH or UID SEARCH command. (Note that the last rule |
| 413 | + might affect ESEARCH implementations that optimize how the COUNT |
| 414 | + result is constructed.) |
| 415 | + |
| 416 | + The following table summarizes the additional requirement on ESEARCH |
| 417 | + server implementations described in this section. |
| 418 | + |
| 419 | + +----------------+-------------------+ |
| 420 | + | Combination of | "$" marker value | |
| 421 | + | Result option | | |
| 422 | + +----------------+-------------------+ |
| 423 | + | SAVE MIN | MIN | |
| 424 | + +----------------+-------------------+ |
| 425 | + | SAVE MAX | MAX | |
| 426 | + +----------------+-------------------+ |
| 427 | + | SAVE MIN MAX | MIN & MAX | |
| 428 | + +----------------+-------------------+ |
| 429 | + | SAVE * [m] | all found messages| |
| 430 | + +----------------+-------------------+ |
| 431 | + |
| 432 | + where '*' means "ALL" and/or "COUNT" |
| 433 | + '[m]' means optional "MIN" and/or "MAX" |
| 434 | + |
| 435 | + |
| 436 | + |
| 437 | + |
| 438 | + |
| 439 | + |
| 440 | + |
| 441 | + |
| 442 | + |
| 443 | + |
| 444 | + |
| 445 | + |
| 446 | + |
| 447 | + |
| 448 | + |
| 449 | + |
| 450 | +Melnikov Standards Track [Page 8] |
| 451 | + |
| 452 | +RFC 5182 Last SEARCH Result Reference March 2008 |
| 453 | + |
| 454 | + |
| 455 | + The following example demonstrates behavioral difference for |
| 456 | + different combinations of ESEARCH result options. Explanatory |
| 457 | + comments start with // and are not part of the protocol: |
| 458 | + |
| 459 | + Example 10: |
| 460 | + C: C282 SEARCH RETURN (ALL) SINCE 12-Feb-2006 |
| 461 | + NOT FROM "Smith" |
| 462 | + S: * ESEARCH (TAG "C283") ALL 2,10:15,21 |
| 463 | + //$ value hasn't changed |
| 464 | + S: C282 OK SEARCH completed |
| 465 | + |
| 466 | + C: C283 SEARCH RETURN (ALL SAVE) SINCE 12-Feb-2006 |
| 467 | + NOT FROM "Smith" |
| 468 | + S: * ESEARCH (TAG "C283") ALL 2,10:15,21 |
| 469 | + //$ value is 2,10:15,21 |
| 470 | + S: C283 OK SEARCH completed |
| 471 | + |
| 472 | + C: C284 SEARCH RETURN (SAVE MIN) SINCE 12-Feb-2006 |
| 473 | + NOT FROM "Smith" |
| 474 | + S: * ESEARCH (TAG "C284") MIN 2 |
| 475 | + //$ value is 2 |
| 476 | + S: C284 OK SEARCH completed |
| 477 | + |
| 478 | + C: C285 SEARCH RETURN (MAX SAVE MIN) SINCE |
| 479 | + 12-Feb-2006 NOT FROM "Smith" |
| 480 | + S: * ESEARCH (TAG "C285") MIN 2 MAX 21 |
| 481 | + //$ value is 2,21 |
| 482 | + S: C285 OK SEARCH completed |
| 483 | + |
| 484 | + C: C286 SEARCH RETURN (MAX SAVE MIN COUNT) |
| 485 | + SINCE 12-Feb-2006 NOT FROM "Smith" |
| 486 | + S: * ESEARCH (TAG "C286") MIN 2 MAX 21 COUNT 8 |
| 487 | + //$ value is 2,10:15,21 |
| 488 | + S: C286 OK SEARCH completed |
| 489 | + |
| 490 | + C: C286 SEARCH RETURN (ALL SAVE MIN) SINCE |
| 491 | + 12-Feb-2006 NOT FROM "Smith" |
| 492 | + S: * ESEARCH (TAG "C286") MIN 2 ALL 2,10:15,21 |
| 493 | + //$ value is 2,10:15,21 |
| 494 | + S: C286 OK SEARCH completed |
| 495 | + |
| 496 | + |
| 497 | + |
| 498 | + |
| 499 | + |
| 500 | + |
| 501 | + |
| 502 | + |
| 503 | + |
| 504 | + |
| 505 | + |
| 506 | +Melnikov Standards Track [Page 9] |
| 507 | + |
| 508 | +RFC 5182 Last SEARCH Result Reference March 2008 |
| 509 | + |
| 510 | + |
| 511 | +2.5. Refusing to Save Search Results |
| 512 | + |
| 513 | + In some cases, the server MAY refuse to save a SEARCH (SAVE) result, |
| 514 | + for example, if an internal limit on the number of saved results is |
| 515 | + reached. |
| 516 | + |
| 517 | + In this case, the server MUST return a tagged NO response containing |
| 518 | + the NOTSAVED response code and set the search result variable to the |
| 519 | + empty sequence, as described in Section 2.1. |
| 520 | + |
| 521 | +3. Formal Syntax |
| 522 | + |
| 523 | + The following syntax specification uses the Augmented Backus-Naur |
| 524 | + Form (ABNF) notation as specified in [ABNF]. Non-terminals |
| 525 | + referenced but not defined below are as defined in [IMAP4] or |
| 526 | + [IMAPABNF]. |
| 527 | + |
| 528 | + Except as noted otherwise, all alphabetic characters are |
| 529 | + case-insensitive. The use of upper- or lower-case characters to |
| 530 | + define token strings is for editorial clarity only. Implementations |
| 531 | + MUST accept these strings in a case-insensitive fashion. |
| 532 | + |
| 533 | + capability =/ "SEARCHRES" |
| 534 | + ;; capability is defined in [IMAP4] |
| 535 | + |
| 536 | + sequence-set =/ seq-last-command |
| 537 | + ;; extends sequence-set to allow for |
| 538 | + ;; "result of the last command" indicator. |
| 539 | + |
| 540 | + seq-last-command = "$" |
| 541 | + |
| 542 | + search-return-opt = "SAVE" |
| 543 | + ;; conforms to generic search-return-opt |
| 544 | + ;; syntax defined in [IMAPABNF] |
| 545 | + |
| 546 | + resp-text-code =/ "NOTSAVED" |
| 547 | + ;; <resp-text-code> from [IMAP4] |
| 548 | + |
| 549 | + |
| 550 | + |
| 551 | + |
| 552 | + |
| 553 | + |
| 554 | + |
| 555 | + |
| 556 | + |
| 557 | + |
| 558 | + |
| 559 | + |
| 560 | + |
| 561 | + |
| 562 | +Melnikov Standards Track [Page 10] |
| 563 | + |
| 564 | +RFC 5182 Last SEARCH Result Reference March 2008 |
| 565 | + |
| 566 | + |
| 567 | +4. Security Considerations |
| 568 | + |
| 569 | + This extension requires the server to keep additional state, that may |
| 570 | + be used to simplify Denial of Service attacks. In order to minimize |
| 571 | + damage from such attacks, server implementations MAY limit the number |
| 572 | + of saved searches they allow across all connections at any given time |
| 573 | + and return the tagged NO response containing the NOTSAVED response |
| 574 | + code (see Section 2.5) to a SEARCH RETURN (SAVE) command when this |
| 575 | + limit is exceeded. |
| 576 | + |
| 577 | + Apart from that, it is believed that this extension doesn't raise any |
| 578 | + additional security concerns not already discussed in [IMAP4]. |
| 579 | + |
| 580 | +5. IANA Considerations |
| 581 | + |
| 582 | + This document defines the "SEARCHRES" IMAP capability. IANA has |
| 583 | + added it to the IMAP4 Capabilities Registry, which is currently |
| 584 | + located at: |
| 585 | + |
| 586 | + http://www.iana.org/assignments/imap4-capabilities |
| 587 | + |
| 588 | +6. Acknowledgments |
| 589 | + |
| 590 | + The author would like to thank Mark Crispin, Cyrus Daboo, and Curtis |
| 591 | + King for remembering that this document had to be written, as well as |
| 592 | + for comments and corrections received. |
| 593 | + |
| 594 | + The author would also like to thank Dave Cridland, Mark Crispin, |
| 595 | + Chris Newman, Dan Karp, and Spencer Dawkins for comments and |
| 596 | + corrections received. |
| 597 | + |
| 598 | + Valuable comments, both in agreement and in dissent, were received |
| 599 | + from Arnt Gulbrandsen. |
| 600 | + |
| 601 | + |
| 602 | + |
| 603 | + |
| 604 | + |
| 605 | + |
| 606 | + |
| 607 | + |
| 608 | + |
| 609 | + |
| 610 | + |
| 611 | + |
| 612 | + |
| 613 | + |
| 614 | + |
| 615 | + |
| 616 | + |
| 617 | + |
| 618 | +Melnikov Standards Track [Page 11] |
| 619 | + |
| 620 | +RFC 5182 Last SEARCH Result Reference March 2008 |
| 621 | + |
| 622 | + |
| 623 | +7. References |
| 624 | + |
| 625 | +7.1. Normative References |
| 626 | + |
| 627 | + [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate |
| 628 | + Requirement Levels", BCP 14, RFC 2119, March 1997. |
| 629 | + |
| 630 | + [ABNF] Crocker, D., Ed., and P. Overell, "Augmented BNF for |
| 631 | + Syntax Specifications: ABNF", STD 68, RFC 5234, January |
| 632 | + 2008. |
| 633 | + |
| 634 | + [IMAP4] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION |
| 635 | + 4rev1", RFC 3501, March 2003. |
| 636 | + |
| 637 | + [IMAPABNF] Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4 |
| 638 | + ABNF", RFC 4466, April 2006. |
| 639 | + |
| 640 | + [ESEARCH] Melnikov, A. and D. Cridland, "IMAP4 Extension to SEARCH |
| 641 | + Command for Controlling What Kind of Information Is |
| 642 | + Returned", RFC 4731, November 2006. |
| 643 | + |
| 644 | +7.2. Informative References |
| 645 | + |
| 646 | + [UIDPLUS] Crispin, M., "Internet Message Access Protocol (IMAP) - |
| 647 | + UIDPLUS extension", RFC 4315, December 2005. |
| 648 | + |
| 649 | + [SORT] Crispin, M. and K. Murchison, "INTERNET MESSAGE ACCESS |
| 650 | + PROTOCOL - SORT AND THREAD EXTENSIONS", Work in Progress, |
| 651 | + Septemeber 2007. |
| 652 | + |
| 653 | +Author's Address |
| 654 | + |
| 655 | + Alexey Melnikov |
| 656 | + Isode Ltd. |
| 657 | + 5 Castle Business Village, |
| 658 | + 36 Station Road, |
| 659 | + Hampton, Middlesex, |
| 660 | + TW12 2BX, United Kingdom |
| 661 | + |
| 662 | + EMail: Alexey.Melnikov@isode.com |
| 663 | + |
| 664 | + |
| 665 | + |
| 666 | + |
| 667 | + |
| 668 | + |
| 669 | + |
| 670 | + |
| 671 | + |
| 672 | + |
| 673 | + |
| 674 | +Melnikov Standards Track [Page 12] |
| 675 | + |
| 676 | +RFC 5182 Last SEARCH Result Reference March 2008 |
| 677 | + |
| 678 | + |
| 679 | +Full Copyright Statement |
| 680 | + |
| 681 | + Copyright (C) The IETF Trust (2008). |
| 682 | + |
| 683 | + This document is subject to the rights, licenses and restrictions |
| 684 | + contained in BCP 78, and except as set forth therein, the authors |
| 685 | + retain all their rights. |
| 686 | + |
| 687 | + This document and the information contained herein are provided on an |
| 688 | + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS |
| 689 | + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND |
| 690 | + THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS |
| 691 | + OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF |
| 692 | + THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED |
| 693 | + WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. |
| 694 | + |
| 695 | +Intellectual Property |
| 696 | + |
| 697 | + The IETF takes no position regarding the validity or scope of any |
| 698 | + Intellectual Property Rights or other rights that might be claimed to |
| 699 | + pertain to the implementation or use of the technology described in |
| 700 | + this document or the extent to which any license under such rights |
| 701 | + might or might not be available; nor does it represent that it has |
| 702 | + made any independent effort to identify any such rights. Information |
| 703 | + on the procedures with respect to rights in RFC documents can be |
| 704 | + found in BCP 78 and BCP 79. |
| 705 | + |
| 706 | + Copies of IPR disclosures made to the IETF Secretariat and any |
| 707 | + assurances of licenses to be made available, or the result of an |
| 708 | + attempt made to obtain a general license or permission for the use of |
| 709 | + such proprietary rights by implementers or users of this |
| 710 | + specification can be obtained from the IETF on-line IPR repository at |
| 711 | + http://www.ietf.org/ipr. |
| 712 | + |
| 713 | + The IETF invites any interested party to bring to its attention any |
| 714 | + copyrights, patents or patent applications, or other proprietary |
| 715 | + rights that may cover technology that may be required to implement |
| 716 | + this standard. Please address the information to the IETF at |
| 717 | + ietf-ipr@ietf.org. |
| 718 | + |
| 719 | + |
| 720 | + |
| 721 | + |
| 722 | + |
| 723 | + |
| 724 | + |
| 725 | + |
| 726 | + |
| 727 | + |
| 728 | + |
| 729 | + |
| 730 | +Melnikov Standards Track [Page 13] |
| 731 | + |
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