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author | Eduardo Chappa <chappa@washington.edu> | 2013-11-02 02:51:18 -0600 |
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committer | Eduardo Chappa <chappa@washington.edu> | 2013-11-02 02:51:18 -0600 |
commit | 7fe712882b909931088a318c08041b0e7974a000 (patch) | |
tree | 2770f9b084e2efc7fc55e96e9bf4352cf2ff33a3 /imap/docs/draft | |
parent | bdfc834badee92ceeb2befe02f1d065ced5b9ddf (diff) | |
download | alpine-7fe712882b909931088a318c08041b0e7974a000.tar.xz |
* Update to version 2.19.1
* Upgrade UW-IMAP to Panda IMAP from https://github.com/jonabbey/panda-imap.
* Replace tabs by spaces in From and Subject fields to control for size in
screen of these fields. Change only in index screen display.
Diffstat (limited to 'imap/docs/draft')
-rw-r--r-- | imap/docs/draft/README | 19 | ||||
-rw-r--r-- | imap/docs/draft/i18n.txt | 1140 | ||||
-rw-r--r-- | imap/docs/draft/sort.txt | 885 |
3 files changed, 0 insertions, 2044 deletions
diff --git a/imap/docs/draft/README b/imap/docs/draft/README deleted file mode 100644 index 9aec4719..00000000 --- a/imap/docs/draft/README +++ /dev/null @@ -1,19 +0,0 @@ -Last Updated: 6 March 2008 - -This directory contains Internet Drafts which, at the time of release of -this software, were not yet been published as RFCs. These documents are -expected to be released as RFCs in the near future. - -This software adheres to the specification in these documents, which -are included for informational purposes. Note, however, that these -documents must be considered preliminary in nature and will be superceded -by the successor RFC. - -File Name I-D Name ---------- -------- -sort.txt draft-ietf-imapext-sort-20.txt - ;; SORT and THREAD commands - ;; Status: approved, blocked waiting for i18n - -i18n.txt draft-ietf-imapext-i18n-15.txt - ;; internationalization in IMAP diff --git a/imap/docs/draft/i18n.txt b/imap/docs/draft/i18n.txt deleted file mode 100644 index f47c6cc7..00000000 --- a/imap/docs/draft/i18n.txt +++ /dev/null @@ -1,1140 +0,0 @@ -
-
-
-
-
-
-Network Working Group Chris Newman
-Internet-Draft Sun Microsystems
-Intended Status: Proposed Standard Arnt Gulbrandsen
- Oryx Mail Systems GmhH
- Alexey Melnikov
- Isode Limited
- February 1, 2008
-
- Internet Message Access Protocol Internationalization
- draft-ietf-imapext-i18n-15.txt
-
-
-Status of this Memo
- By submitting this Internet-Draft, each author represents that any
- applicable patent or other IPR claims of which he or she is aware
- have been or will be disclosed, and any of which he or she becomes
- aware will be disclosed, in accordance with Section 6 of BCP 79.
-
- Internet-Drafts are working documents of the Internet Engineering
- Task Force (IETF), its areas, and its working groups. Note that
- other groups may also distribute working documents as Internet-
- Drafts.
-
- Internet-Drafts are draft documents valid for a maximum of six
- months and may be updated, replaced, or obsoleted by other documents
- at any time. It is inappropriate to use Internet-Drafts as
- reference material or to cite them other than as "work in progress".
-
- The list of current Internet-Drafts can be accessed at
- http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-
- Draft Shadow Directories can be accessed at
- http://www.ietf.org/shadow.html.
-
- This Internet-Draft expires in August 2008.
-
-
-Copyright Notice
-
- Copyright (C) The IETF Trust (2008).
-
-
-Abstract
-
- Internet Message Access Protocol (IMAP) version 4rev1 has basic
- support for non-ASCII characters in mailbox names and search
- substrings. It also supports non-ASCII message headers and content
- encoded as specified by Multipurpose Internet Mail Extensions
- (MIME). This specification defines a collection of IMAP extensions
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- which improve international support including comparator negotiation
- for search, sort and thread, language negotiation for international
- error text, and translations for namespace prefixes.
-
-
-Table of Contents
-
- 1. Conventions Used in this Document . . . . . . . . . . . . . . 2
- 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
- 3. LANGUAGE Extension . . . . . . . . . . . . . . . . . . . . . 3
- 3.1 LANGUAGE Extension Requirements . . . . . . . . . . . . . . . 3
- 3.2 LANGUAGE Command . . . . . . . . . . . . . . . . . . . . . . 4
- 3.3 LANGUAGE Response . . . . . . . . . . . . . . . . . . . . . . 6
- 3.4 TRANSLATION Extension to the NAMESPACE Response . . . . . . . 6
- 3.5 Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 6
- 4. I18NLEVEL=1 and I18NLEVEL=2 Extensions . . . . . . . . . . . 7
- 4.1 Introduction and Overview . . . . . . . . . . . . . . . . . . 8
- 4.2 Requirements common to both I18NLEVEL=1 and I18NLEVEL=2 . . .
- 4.3 I18NLEVEL=1 Extension Requirements . . . . . . . . . . . . . 8
- 4.4 I18NLEVEL=2 Extension Requirements . . . . . . . . . . . . . 8
- 4.5 Compatibility Notes
- 4.6 Comparators and Charsets . . . . . . . . . . . . . . . . . . 9
- 4.7 COMPARATOR Command . . . . . . . . . . . . . . . . . . . . . 9
- 4.8 COMPARATOR Response . . . . . . . . . . . . . . . . . . . . . 10
- 4.9 BADCOMPARATOR Response Code . . . . . . . . . . . . . . . . .
- 4.10 Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . 10
- 5. Other IMAP Internationalization Issues . . . . . . . . . . . 11
- 5.1 UTF-8 Userids and Passwords . . . . . . . . . . . . . . . . . 11
- 5.2 UTF-8 Mailbox Names . . . . . . . . . . . . . . . . . . . . . 11
- 5.3 UTF-8 Domains, Addresses and Mail Headers . . . . . . . . . . 11
- 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
- 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
- 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
- 9. Relevant Standards for i18n IMAP Implementations . . . . . . 13
- Normative References . . . . . . . . . . . . . . . . . . . . 13
- Informative References . . . . . . . . . . . . . . . . . . . 14
- Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 15
- Intellectual Property and Copyright Statements . . . . . . . 16
-
-
-Conventions Used in This Document
-
- 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 [RFC2119].
-
- The formal syntax use the Augmented Backus-Naur Form (ABNF)
- [RFC4234] notation including the core rules defined in Appendix A.
-
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- The UTF8-related productions are defined in [RFC3629].
-
- In examples, "C:" and "S:" indicate lines sent by the client and
- server respectively. If a single "C:" or "S:" label applies to
- multiple lines, then the line breaks between those lines are for
- editorial clarity only and are not part of the actual protocol
- exchange.
-
-
-2. Introduction
-
- This specification defines two IMAP4rev1 [RFC3501] extensions to
- enhance international support. These extensions can be advertised
- and implemented separately.
-
- The LANGUAGE extension allows the client to request a suitable
- language for protocol error messages and in combination with the
- NAMESPACE extension [RFC2342] enables namespace translations.
-
- The I18NLEVEL=2 extension allows the client to request a suitable
- collation which will modify the behavior of the base specification's
- SEARCH command as well as the SORT and THREAD extensions [SORT].
- This leverages the collation registry [RFC4790].
-
-
-3. LANGUAGE Extension
-
- IMAP allows server responses to include human-readable text that in
- many cases needs to be presented to the user. But that text is
- limited to US-ASCII by the IMAP specification [RFC3501] in order to
- preserve backwards compatibility with deployed IMAP implementations.
- This section specifies a way for an IMAP client to negotiate which
- language the server should use when sending human-readable text.
-
- The LANGUAGE extension only provides a mechanism for altering fixed
- server strings such as response text and NAMESPACE folder names.
- Assigning localized language aliases to shared mailboxes would be
- done with a separate mechanism such as the proposed METADATA
- extension (see [METADATA]).
-
-
-3.1 LANGUAGE Extension Requirements
-
- IMAP servers that support this extension MUST list the keyword
- LANGUAGE in their CAPABILITY response as well as in the greeting
- CAPABILITY data.
-
- A server that advertises this extension MUST use the language "i-
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- default" as described in [RFC2277] as its default language until
- another supported language is negotiated by the client. A server
- MUST include "i-default" as one of its supported languages.
-
- Clients and servers that support this extension MUST also support
- the NAMESPACE extension [RFC2342].
-
- The LANGUAGE command is valid in all states. Clients are urged to
- issue LANGUAGE before authentication, since some servers send
- valuable user information as part of authentication (e.g. "password
- is correct, but expired"). If a security layer (such as SASL or
- TLS) is subsequently negotiated by the client, it MUST re-issue the
- LANGUAGE command in order to make sure that no previous active
- attack (if any) on LANGUAGE negotiation has effect on subsequent
- error messages. (See Section 7 for a more detailed explanation of
- the attack.)
-
-
-
-3.2 LANGUAGE Command
-
- Arguments: Optional language range arguments.
-
- Response: A possible LANGUAGE response (see section 3.3).
- A possible NAMESPACE response (see section 3.4).
-
- Result: OK - Command completed
- NO - Could not complete command
- BAD - arguments invalid
-
- The LANGUAGE command requests that human-readable text emitted by
- the server be localized to a language matching one of the language
- range argument as described by section 2 of [RFC4647].
-
- If the command succeeds, the server will return human-readable
- responses in the first supported language specified. These
- responses will be in UTF-8 [RFC3629]. The server MUST send a
- LANGUAGE response specifying the language used, and the change takes
- effect immediately after the LANGUAGE response.
-
- If the command fails, the server continues to return human-readable
- responses in the language it was previously using.
-
- The special "default" language range argument indicates a request to
- use a language designated as preferred by the server administrator.
- The preferred language MAY vary based on the currently active user.
-
- If a language range does not match a known language tag exactly but
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- does match a language by the rules of [RFC4647], the server MUST
- send an untagged LANGUAGE response indicating the language selected.
-
- If there aren't any arguments, the server SHOULD send an untagged
- LANGUAGE response listing the languages it supports. If the server
- is unable to enumerate the list of languages it supports it MAY
- return a tagged NO response to the enumeration request.
-
- < The server defaults to using English i-default responses until
- the user explicitly changes the language. >
-
- C: A001 LOGIN KAREN PASSWORD
- S: A001 OK LOGIN completed
-
- < Client requested MUL language, which no server supports. >
-
- C: A002 LANGUAGE MUL
- S: A002 NO Unsupported language MUL
-
- < A LANGUAGE command with no arguments is a request to enumerate
- the list of languages the server supports. >
-
- C: A003 LANGUAGE
- S: * LANGUAGE (EN DE IT i-default)
- S: A003 OK Supported languages have been enumerated
-
- C: B001 LANGUAGE
- S: B001 NO Server is unable to enumerate supported languages
-
- < Once the client changes the language, all responses will be in
- that language starting after the LANGUAGE response. Note that
- this includes the NAMESPACE response. Because RFCs are in US-
- ASCII, this document uses an ASCII transcription rather than
- UTF-8 text, e.g. ue in the word "ausgefuehrt" >
-
- C: C001 LANGUAGE DE
- S: * LANGUAGE (DE)
- S: * NAMESPACE (("" "/")) (("Other Users/" "/" "TRANSLATION"
- ("Andere Ben&APw-tzer/"))) (("Public Folders/" "/"
- "TRANSLATION" ("Gemeinsame Postf&AM8-cher/")))
- S: C001 OK Sprachwechsel durch LANGUAGE-Befehl ausgefuehrt
-
- < If a server does not support the requested primary language,
- responses will continue to be returned in the current language
- the server is using. >
-
- C: D001 LANGUAGE FR
- S: D001 NO Diese Sprache ist nicht unterstuetzt
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- C: D002 LANGUAGE DE-IT
- S: * LANGUAGE (DE-IT)
- S: * NAMESPACE (("" "/"))(("Other Users/" "/" "TRANSLATION"
- ("Andere Ben&APw-tzer/"))) (("Public Folders/" "/"
- "TRANSLATION" ("Gemeinsame Postf&AM8-cher/")))
- S: D002 OK Sprachwechsel durch LANGUAGE-Befehl ausgefuehrt
- C: D003 LANGUAGE "default"
- S: * LANGUAGE (DE)
- S: D003 OK Sprachwechsel durch LANGUAGE-Befehl ausgefuehrt
-
- < Server does not speak French, but does speak English. User
- speaks Canadian French and Canadian English. >
-
- C: E001 LANGUAGE FR-CA EN-CA
- S: * LANGUAGE (EN)
- S: E001 OK Now speaking English
-
-
-
-3.3 LANGUAGE Response
-
- Contents: A list of one or more language tags.
-
- The LANGUAGE response occurs as a result of a LANGUAGE command. A
- LANGUAGE response with a list containing a single language tag
- indicates that the server is now using that language. A LANGUAGE
- response with a list containing multiple language tags indicates the
- server is communicating a list of available languages to the client,
- and no change in the active language has been made.
-
-
-3.4 TRANSLATION Extension to the NAMESPACE Response
-
- If localized representations of the namespace prefixes are available
- in the selected language, the server SHOULD include these in the
- TRANSLATION extension to the NAMESPACE response.
-
- The TRANSLATION extension to the NAMESPACE response returns a single
- string, containing the modified UTF-7 [RFC3501] encoded translation
- of the namespace prefix. It is the responsibility of the client to
- convert between the namespace prefix and the translation of the
- namespace prefix when presenting mailbox names to the user.
-
- In this example a server supports the IMAP4 NAMESPACE command. It
- uses no prefix to the user's Personal Namespace, a prefix of "Other
- Users" to its Other Users' Namespace and a prefix of "Public
- Folders" to its only Shared Namespace. Since a client will often
- display these prefixes to the user, the server includes a
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- translation of them that can be presented to the user.
-
- C: A001 LANGUAGE DE-IT
- S: * NAMESPACE (("" "/")) (("Other Users/" "/" "TRANSLATION"
- ("Andere Ben&APw-tzer/"))) (("Public Folders/" "/"
- "TRANSLATION" ("Gemeinsame Postf&AM8-cher/")))
- S: A001 OK LANGUAGE-Befehl ausgefuehrt
-
-
-3.5 Formal Syntax
-
- The following syntax specification inherits ABNF [RFC4234] rules
- from IMAP4rev1 [RFC3501], IMAP4 Namespace [RFC2342], Tags for the
- Identifying Languages [RFC4646], UTF-8 [RFC3629] and Collected
- Extensions to IMAP4 ABNF [RFC4466].
-
- command-any =/ language-cmd
- ; LANGUAGE command is valid in all states
-
- language-cmd = "LANGUAGE" *(SP lang-range-quoted)
-
- response-payload =/ language-data
-
- language-data = "LANGUAGE" SP "(" lang-tag-quoted *(SP
- lang-tag-quoted) ")"
-
- namespace-trans = SP DQUOTE "TRANSLATION" DQUOTE SP "(" string ")"
- ; the string is encoded in Modified UTF-7.
- ; this is a subset of the syntax permitted by
- ; the Namespace-Response-Extension rule in [RFC4466]
-
- lang-range-quoted = astring
- ; Once any literal wrapper or quoting is removed, this
- ; follows the language-range rule in [RFC4647]
-
- lang-tag-quoted = astring
- ; Once any literal wrapper or quoting is removed, this follows
- ; the Language-Tag rule in [RFC4646]
-
- resp-text = ["[" resp-text-code "]" SP ] UTF8-TEXT-CHAR
- *(UTF8-TEXT-CHAR / "[")
- ; After the server is changed to a language other than
- ; i-default, this resp-text rule replaces the resp-text
- ; rule from [RFC3501].
-
- UTF8-TEXT-CHAR = %x20-5A / %x5C-7E / UTF8-2 / UTF8-3 / UTF8-4
- ; UTF-8 excluding 7-bit control characters and "["
-
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-4. I18NLEVEL=1 and I18NLEVEL=2 Extensions
-
-
-4.1 Introduction and Overview
-
- IMAP4rev1 [RFC3501] includes the SEARCH command which can be used to
- locate messages matching criteria including human-readable text.
- The SORT extension [SORT] to IMAP allows the client to ask the
- server to determine the order of messages based on criteria
- including human-readable text. These mechanisms require the ability
- to support non-English search and sort functions.
-
- Section 4 defines two IMAP extensions for internationalizing IMAP
- SEARCH, SORT and THREAD [SORT] using the comparator framework
- [RFC4790].
-
- The I18NLEVEL=1 extension updates SEARCH/SORT/THREAD to use
- i;unicode-casemap comparator, as defined in [UCM]. See Sections 4.2
- and 4.3 for more details.
-
- The I18NLEVEL=2 extension is a superset of the I18NLEVEL=1
- extension. It adds to I18NLEVEL=1 extension the ability to determine
- the active comparator (see definition below) and negotiate use of
- comparators using the COMPARATOR command. It also adds the
- COMPARATOR response that indicates the active comparator and
- possibly other available comparators. See Sections 4.2 and 4.4 for
- more details.
-
-
-4.2 Requirements common to both I18NLEVEL=1 and I18NLEVEL=2
-
- The term "default comparator" refers to the comparator which is used
- by SEARCH and SORT absent any negotiation using the COMPARATOR (see
- Section 4.7) command. The term "active comparator" refers to the
- comparator which will be used within a session e.g. by SEARCH and
- SORT. The COMPARATOR command is used to change the active
- comparator.
-
- The active comparator applies to the following SEARCH keys: "BCC",
- "BODY", "CC", "FROM", "SUBJECT", "TEXT", "TO" and "HEADER". If the
- server also advertises the "SORT" extension, then the active
- comparator applies to the following SORT keys: "CC", "FROM",
- "SUBJECT" and "TO". If the server advertises THREAD=ORDEREDSUBJECT,
- then the active comparator applies to the ORDEREDSUBJECT threading
- algorithm. If the server advertises THREAD=REFERENCES, then the
- active comparator applies to the subject field comparisons done by
- REFERENCES threading algorithm. Future extensions may choose to
- apply the active comparator to their SEARCH keys.
-
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- For SORT and THREAD, the pre-processing necessary to extract the
- base subject text from a Subject header occurs prior to the
- application of a comparator.
-
- A server that advertises I18NLEVEL=1 or I18NLEVEL=2 extension MUST
- implement the i;unicode-casemap comparator, as defined in [UCM].
-
- A server that advertises I18NLEVEL=1 or I18NLEVEL=2 extension MUST
- support UTF-8 as a SEARCH charset.
-
-
-4.3 I18NLEVEL=1 Extension Requirements
-
- An IMAP server that satisfies all requirements specified in sections
- 4.2 and 4.6 (and doesn't support/advertise any other I18NLEVEL=<n>
- extension, where n > 1) MUST list the keyword I18NLEVEL=1 in its
- CAPABILITY data once IMAP enters the authenticated state, and MAY
- list that keyword in other states.
-
-
-
-4.4 I18NLEVEL=2 Extension Requirements
-
- IMAP server that satisfies all requirements specified in sections
- 4.2, 4.4, 4.6-4.10 (and doesn't support/advertise any other
- I18NLEVEL=<n> extension, where n > 2) MUST list the keyword
- I18NLEVEL=2 in its CAPABILITY data once IMAP enters the
- authenticated state, and MAY list that keyword in other states.
-
- A server that advertises this extension MUST implement the
- i;unicode-casemap comparator, as defined in [UCM]. It MAY implement
- other comparators from the IANA registry established by [RFC4790].
- See also section 4.5 of this document.
-
- A server that advertises this extension SHOULD use i;unicode-casemap
- as the default comparator. (Note that i;unicode-casemap is the
- default comparator for I18NLEVEL=1, but not necessarily the default
- for I18NLEVEL=2.) The selection of the default comparator MAY be
- adjustable by the server administrator, and MAY be sensitive to the
- current user. Once the IMAP connection enters authenticated state,
- the default comparator MUST remain static for the remainder of that
- connection.
-
- Note that since SEARCH uses the substring operation, IMAP servers
- can only implement collations that offer the substring operation
- (see [RFC4790 section 4.2.2). Since SORT uses ordering operation
- (and by implication equality), IMAP servers which advertise the SORT
- extension can only implement collations that offer all three
-
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- operations (see [RFC4790] sections 4.2.2-4).
-
- If the active collation does not provide the operations needed by an
- IMAP command, the server MUST respond with a tagged BAD.
-
-
-4.5 Compatibility Notes
-
- Several server implementations deployed prior to the publication of
- this specification comply with I18NLEVEL=1 (see section 4.3), but do
- not advertise that. Other legacy servers use the i;ascii-casemap
- (see [RFC4790]) comparator.
-
- There is no good way for a client to know which comparator that a
- legacy server uses. If the client has to assume the worst, it may
- end up doing expensive local operations to obtain i;unicode-casemap
- comparisons even though the server implements it.
-
- Legacy server implementations which comply with I18NLEVEL=1 should
- be updated to advertise I18NLEVEL=1. All server implementations
- should eventually be updated to comply with the I18NLEVEL=2
- extension.
-
-
-4.6 Comparators and Character Encodings
-
- RFC 3501, section 6.4.4 says:
-
- In all search keys that use strings, a message matches
- the key if the string is a substring of the field. The
- matching is case-insensitive.
-
- When performing the SEARCH operation, the active comparator is
- applied instead of the case-insensitive matching specified above.
-
- An IMAP server which performs collation operations (e.g., as part of
- commands such as SEARCH, SORT, THREAD) does so according to the
- following procedure:
-
- (a) MIME encoding (for example see [RFC2047] for headers and
- [RFC2045] for body parts) MUST be removed in the texts being
- collated.
-
- If MIME encoding removal fails for a message (e.g., a body part
- of the message has an unsupported Content-Transfer-Encoding,
- uses characters not allowed by the Content-Transfer-Encoding,
- etc.), the collation of this message is undefined by this
- specification, and is handled in an implementation-dependent
-
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- manner.
-
- (b) The decoded text from (a) MUST be converted to the charset
- expected by the active comparator.
-
- (c) For the substring operation:
- If step (b) failed (e.g., the text is in an unknown charset,
- contains a sequence which is not valid according in that
- charset, etc.), the original decoded text from (a) (i.e.,
- before the charset conversion attempt) is collated using the
- i;octet comparator (see [RFC4790]).
-
- If step (b) was successful, the converted text from (b) is
- collated according to the active comparator.
-
-
- For the ordering operation:
-
- All strings that were successfully converted by step (b) are
- separated from all strings that failed step (b). Strings in
- each group are collated independently. All strings successfully
- converted by step (b) are then validated by the active
- comparator. Strings that pass validation are collated using the
- active comparator. All strings that either fail step (b) or fail
- the active collation's validity operation are collated (after
- applying step (a)) using the i;octet comparator (see [RFC4790]).
- The resulting sorted list is produced by appending all collated
- "failed" strings after all strings collated using the active
- comparator.
-
-
- Example: The following example demonstrates ordering of 4
- different strings using i;unicode-casemap [UCM] comparator.
- Strings are represented using hexadecimal notation used by
- ABNF [RFC4234].
-
- (1) %xD0 %xC0 %xD0 %xBD %xD0 %xB4 %xD1 %x80 %xD0 %xB5
- %xD0 %xB9 (labeled with charset=UTF-8)
- (2) %xD1 %x81 %xD0 %x95 %xD0 %xA0 %xD0 %x93 %xD0 %x95
- %xD0 %x99 (labeled with charset=UTF-8)
- (3) %xD0 %x92 %xD0 %xB0 %xD1 %x81 %xD0 %xB8 %xD0 %xBB
- %xD0 %xB8 %xFF %xB9 (labeled with charset=UTF-8)
- (4) %xE1 %xCC %xC5 %xCB %xD3 %xC5 %xCA (labeled with
- charset=KOI8-R)
-
- Step (b) will convert string # 4 to the following
- sequence of octets (in UTF-8):
-
-
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- %xD0 %x90 %xD0 %xBB %xD0 %xB5 %xD0 %xBA %xD1 %x81 %xD0
- %xB5 %xD0 %xB9
-
- and will reject strings (1) and (3), as they contain
- octets not allowed in charset=UTF-8.
- After that, using the i;unicode-casemap collation,
- string (4) will collate before string (2). Using the
- i;octet collation on the original strings, string (3)
- will collate before string (1). So the final ordering
- is as follows: (4) (2) (3) (1).
-
- If the substring operation (e.g., IMAP SEARCH) of the active
- comparator returns the "undefined" result (see section 4.2.3 of
- [RFC4790]) for either the text specified in the SEARCH command or
- the message text, then the operation is repeated on the result of
- step (a) using the i;octet comparator.
-
- The ordering operation (e.g., IMAP SORT and THREAD) SHOULD collate
- the following together: strings encoded using unknown or invalid
- character encodings, strings in unrecognized charsets, and invalid
- input (as defined by the active collation).
-
-
-
-4.7 COMPARATOR Command
-
- Arguments: Optional comparator order arguments.
-
- Response: A possible COMPARATOR response (see Section 4.8).
-
- Result: OK - Command completed
- NO - No matching comparator found
- BAD - arguments invalid
-
- The COMPARATOR command is valid in authenticated and selected
- states.
-
- The COMPARATOR command is used to determine or change the active
- comparator. When issued with no arguments, it results in a
- COMPARATOR response indicating the currently active comparator.
-
- When issued with one or more comparator argument, it changes the
- active comparator as directed. (If more than one installed
- comparator is matched by an argument, the first argument wins.) The
- COMPARATOR response lists all matching comparators if more than one
- matches the specified patterns.
-
- The argument "default" refers to the server's default comparator.
-
-
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- Otherwise each argument is an collation specification as defined in
- the Internet Application Protocol Comparator Registry [RFC4790].
-
- < The client requests activating a Czech comparator if possible,
- or else a generic international comparator which it considers
- suitable for Czech. The server picks the first supported
- comparator. >
-
- C: A001 COMPARATOR "cz;*" i;basic
- S: * COMPARATOR i;basic
- S: A001 OK Will use i;basic for collation
-
-
-4.8 COMPARATOR Response
-
- Contents: The active comparator.
- An optional list of available matching comparators
-
- The COMPARATOR response occurs as a result of a COMPARATOR command.
- The first argument in the comparator response is the name of the
- active comparator. The second argument is a list of comparators
- which matched any of the arguments to the COMPARATOR command and is
- present only if more than one match is found.
-
-
-4.9 BADCOMPARATOR response code
-
- This response code SHOULD be returned as a result of server failing
- an IMAP command (returning NO), when the server knows that none of
- the specified comparators match the requested comparator(s).
-
-
-4.10 Formal Syntax
-
- The following syntax specification inherits ABNF [RFC4234] rules
- from IMAP4rev1 [RFC3501], and Internet Application Protocol
- Comparator Registry [RFC4790].
-
- command-auth =/ comparator-cmd
-
- resp-text-code =/ "BADCOMPARATOR"
-
- comparator-cmd = "COMPARATOR" *(SP comp-order-quoted)
-
- response-payload =/ comparator-data
-
- comparator-data = "COMPARATOR" SP comp-sel-quoted [SP "("
- comp-id-quoted *(SP comp-id-quoted) ")"]
-
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- comp-id-quoted = astring
- ; Once any literal wrapper or quoting is removed, this
- ; follows the collation-id rule from [RFC4790]
-
- comp-order-quoted = astring
- ; Once any literal wrapper or quoting is removed, this
- ; follows the collation-order rule from [RFC4790]
-
- comp-sel-quoted = astring
- ; Once any literal wrapper or quoting is removed, this
- ; follows the collation-selected rule from [RFC4790]
-
-
-5. Other IMAP Internationalization Issues
-
- The following sections provide an overview of various other IMAP
- internationalization issues. These issues are not resolved by this
- specification, but could be resolved by other standards work, such
- as that being done by the EAI group (see [IMAP-EAI]).
-
-
-5.1 Unicode Userids and Passwords
-
- IMAP4rev1 currently restricts the userid and password fields of the
- LOGIN command to US-ASCII. The "userid" and "password" fields of the
- IMAP LOGIN command are restricted to US-ASCII only until a future
- standards track RFC states otherwise. Servers are encouraged to
- validate both fields to make sure they conform to the formal syntax
- of UTF-8 and to reject the LOGIN command if that syntax is violated.
- Servers MAY reject the use of any 8-bit in the "userid" or
- "password" field.
-
- When AUTHENTICATE is used, some servers may support userids and
- passwords in Unicode [RFC3490] since SASL (see [RFC4422]) allows
- that. However, such userids cannot be used as part of email
- addresses.
-
-
-5.2 UTF-8 Mailbox Names
-
- The modified UTF-7 mailbox naming convention described in section
- 5.1.3 of RFC 3501 is best viewed as an transition from the status
- quo in 1996 when modified UTF-7 was first specified. At that time,
- there was widespread unofficial use of local character sets such as
- ISO-8859-1 and Shift-JIS for non-ASCII mailbox names, with resultant
- non-interoperability.
-
- The requirements in section 5.1 of RFC 3501 are very important if
-
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- we're ever going to be able to deploy UTF-8 mailbox names. Servers
- are encouraged to enforce them.
-
-
-5.3 UTF-8 Domains, Addresses and Mail Headers
-
- There is now an IETF standard for Internationalizing Domain Names in
- Applications [RFC3490]. While IMAP clients are free to support this
- standard, an argument can be made that it would be helpful to simple
- clients if the IMAP server could perform this conversion (the same
- argument would apply to MIME header encoding [RFC2047]). However,
- it would be unwise to move forward with such work until the work in
- progress to define the format of international email addresses is
- complete.
-
-
-6. IANA Considerations
-
- The IANA is requested to add LANGUAGE, I18NLEVEL=1 and I18NLEVEL=2
- to the IMAP4 Capabilities Registry. [Note to IANA:
- http://www.iana.org/assignments/imap4-capabilities]
-
-
-7. Security Considerations
-
- The LANGUAGE extension makes a new command available in "Not
- Authenticated" state in IMAP. Some IMAP implementations run with
- root privilege when the server is in "Not Authenticated" state and
- do not revoke that privilege until after authentication is complete.
- Such implementations are particularly vulnerable to buffer overflow
- security errors at this stage and need to implement parsing of this
- command with extra care.
-
- A LANGUAGE command issued prior to activation of a security layer is
- subject to an active attack which suppresses or modifies the
- negotiation and thus makes STARTTLS or authentication error messages
- more difficult to interpret. This is not a new attack as the error
- messages themselves are subject to active attack. Clients MUST re-
- issue the LANGUAGE command once a security layer is active, so this
- does not impact subsequent protocol operations.
-
- LANGUAGE, I18NLEVEL=1 and I18NLEVEL=2 extensions use the UTF-8
- charset, thus the security considerations for UTF-8 [RFC3629] are
- relevent. However, neither uses UTF-8 for identifiers so the most
- serious concerns do not apply.
-
-
-8. Acknowledgements
-
-
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- The LANGUAGE extension is based on a previous Internet draft by Mike
- Gahrns, a substantial portion of the text in that section was
- written by him. Many people have participated in discussions about
- an IMAP Language extension in the various fora of the IETF and
- Internet working groups, so any list of contributors is bound to be
- incomplete. However, the authors would like to thank Andrew McCown
- for early work on the original proposal, John Myers for suggestions
- regarding the namespace issue, along with Jutta Degener, Mark
- Crispin, Mark Pustilnik, Larry Osterman, Cyrus Daboo, Martin Duerst,
- Timo Sirainen, Ben Campbell and Magnus Nystrom for their many
- suggestions that have been incorporated into this document.
-
- Initial discussion of the I18NLEVEL=2 extension involved input from
- Mark Crispin and other participants of the IMAP Extensions WG.
-
-
-9. Relevant Standards for i18n IMAP Implementations
-
- This is a non-normative list of standards to consider when
- implementing i18n aware IMAP software.
-
- o The LANGUAGE and I18NLEVEL=2 extensions to IMAP (this
- specification).
- o The 8-bit rules for mailbox naming in section 5.1 of RFC 3501.
- o The Mailbox International Naming Convention in section 5.1.3 of
- RFC 3501.
- o MIME [RFC2045] for message bodies.
- o MIME header encoding [RFC2047] for message headers.
- o The IETF EAI working group.
- o MIME Parameter Value and Encoded Word Extensions [RFC2231] for
- filenames. Quality IMAP server implementations will
- automatically combine multipart parameters when generating the
- BODYSTRUCTURE. There is also some deployed non-standard use of
- MIME header encoding inside double-quotes for filenames.
- o IDNA [RFC3490] and punycode [RFC3492] for domain names
- (currently only relevant to IMAP clients).
- o The UTF-8 charset [RFC3629].
- o The IETF policy on Character Sets and Languages [RFC2277].
-
-
-Normative References
-
- [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [RFC2277] Alvestrand, "IETF Policy on Character Sets and
- Languages", BCP 18, RFC 2277, January 1998.
-
-
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- [RFC2342] Gahrns, Newman, "IMAP4 Namespace", RFC 2342, May 1998.
-
- [RFC3501] Crispin, "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
- 4rev1", RFC 3501, March 2003.
-
- [RFC3629] Yergeau, "UTF-8, a transformation format of ISO 10646",
- STD 63, RFC 3629, November 2003.
-
- [RFC4234] Crocker, Overell, "Augmented BNF for Syntax
- Specifications: ABNF", RFC 4234, Brandenburg
- Internetworking, Demon Internet Ltd, October 2005.
-
- [RFC4422] Melnikov, Zeilenga, "Simple Authentication and Security
- Layer (SASL)", RFC 4422, June 2006.
-
- [RFC4466] Melnikov, Daboo, "Collected Extensions to IMAP4 ABNF",
- RFC 4466, Isode Ltd., April 2006.
-
- [RFC4646] Philips, Davis, "Tags for Identifying Languages", BCP 47,
- RFC 4646, September 2006.
-
- [RFC4647] Philips, Davis, "Matching of Language Tags", BCP 47, RFC
- 4647, September 2006.
-
- [RFC4790] Newman, Duerst, Gulbrandsen, "Internet Application
- Protocol Comparator Registry", RFC 4790, February 2007.
-
- [SORT] Crispin, M. and K. Murchison, "INTERNET MESSAGE ACCESS
- PROTOCOL - SORT AND THREAD EXTENSION", draft-ietf-
- imapext-sort-19 (work in progress), November 2006.
-
- [UCM] Crispin, "i;unicode-casemap - Simple Unicode Collation
- Algorithm", RFC 5051, October 2007.
-
- [RFC2045] Freed, Borenstein, "Multipurpose Internet Mail Extensions
- (MIME) Part One: Format of Internet Message Bodies", RFC
- 2045, November 1996.
-
- [RFC2047] Moore, "MIME (Multipurpose Internet Mail Extensions) Part
- Three: Message Header Extensions for Non-ASCII Text", RFC
- 2047, November 1996.
-
-
-Informative References
-
-
- [RFC2231] Freed, Moore, "MIME Parameter Value and Encoded Word
- Extensions: Character Sets, Languages, and
-
-
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- Continuations", RFC 2231, November 1997.
-
- [RFC3490] Faltstrom, Hoffman, Costello, "Internationalizing Domain
- Names in Applications (IDNA)", RFC 3490, March 2003.
-
- [RFC3492] Costello, "Punycode: A Bootstring encoding of Unicode for
- Internationalized Domain Names in Applications (IDNA)",
- RFC 3492, March 2003.
-
- [METADATA] Daboo, C., "IMAP METADATA Extension", draft-daboo-imap-
- annotatemore-12 (work in progress), December 2007.
-
- [IMAP-EAI] Resnick, Newman, "IMAP Support for UTF-8", draft-ietf-
- eai-imap-utf8 (work in progress), May 2006.
-
-
-
-Authors' Addresses
-
- Chris Newman
- Sun Microsystems
- 3401 Centrelake Dr., Suite 410
- Ontario, CA 91761
- US
-
- Email: chris.newman@sun.com
-
-
- Arnt Gulbrandsen
- Oryx Mail Systems GmbH
- Schweppermannstr. 8
- D-81671 Muenchen
- Germany
-
- Email: arnt@oryx.com
-
- Fax: +49 89 4502 9758
-
-
- Alexey Melnikov
- Isode Limited
- 5 Castle Business Village, 36 Station Road,
- Hampton, Middlesex, TW12 2BX, UK
-
- Email: Alexey.Melnikov@isode.com
-
-
-
-
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-Intellectual Property Statement
-
- The IETF takes no position regarding the validity or scope of any
- Intellectual Property Rights or other rights that might be claimed to
- pertain to the implementation or use of the technology described in
- this document or the extent to which any license under such rights
- might or might not be available; nor does it represent that it has
- made any independent effort to identify any such rights. Information
- on the procedures with respect to rights in RFC documents can be found
- in BCP 78 and BCP 79.
-
- Copies of IPR disclosures made to the IETF Secretariat and any
- assurances of licenses to be made available, or the result of an
- attempt made to obtain a general license or permission for the use of
- such proprietary rights by implementers or users of this specification
- can be obtained from the IETF on-line IPR repository at
- http://www.ietf.org/ipr.
-
- The IETF invites any interested party to bring to its attention any
- copyrights, patents or patent applications, or other proprietary
- rights that may cover technology that may be required to implement
- this standard. Please address the information to the IETF at
- ietf-ipr@ietf.org.
-
-
-Full Copyright Statement
-
- Copyright (C) The IETF Trust (2008). This document is subject to
- the rights, licenses and restrictions contained in BCP 78, and
- except as set forth therein, the authors retain all their rights.
-
- This document and the information contained herein are provided on
- an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
- REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE
- IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL
- WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
- WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE
- ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
- FOR A PARTICULAR PURPOSE.
-
-
-Acknowledgment
-
- Funding for the RFC Editor function is currently provided by the
- Internet Society.
-
-
-
-
-
-
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diff --git a/imap/docs/draft/sort.txt b/imap/docs/draft/sort.txt deleted file mode 100644 index 4453bb4d..00000000 --- a/imap/docs/draft/sort.txt +++ /dev/null @@ -1,885 +0,0 @@ -IMAP Extensions Working Group M. Crispin -Internet-Draft K. Murchison -Intended status: Proposed Standard March 10, 2008 -Expires: September 10, 2008 -Document: internet-drafts/draft-ietf-imapext-sort-20.txt - - INTERNET MESSAGE ACCESS PROTOCOL - SORT AND THREAD EXTENSIONS - -Status of this Memo - - By submitting this Internet-Draft, each author represents that - any applicable patent or other IPR claims of which he or she is - aware have been or will be disclosed, and any of which he or she - becomes aware will be disclosed, in accordance with Section 6 of - BCP 79. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as - Internet-Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - A revised version of this draft document will be submitted to the RFC - editor as a Proposed Standard for the Internet Community. Discussion - and suggestions for improvement are requested, and should be sent to - ietf-imapext@IMC.ORG. - - Distribution of this memo is unlimited. - -Abstract - - This document describes the base-level server-based sorting and - threading extensions to the [IMAP] protocol. These extensions - provide substantial performance improvements for IMAP clients which - offer sorted and threaded views. - -1. Introduction - - The SORT and THREAD extensions to the [IMAP] protocol provide a means - of server-based sorting and threading of messages, without requiring - that the client download the necessary data to do so itself. This is - particularly useful for online clients as described in [IMAP-MODELS]. - - A server which supports the base-level SORT extension indicates this - with a capability name which starts with "SORT". Future, - upwards-compatible extensions to the SORT extension will all start - with "SORT", indicating support for this base level. - - A server which supports the THREAD extension indicates this with one - or more capability names consisting of "THREAD=" followed by a - supported threading algorithm name as described in this document. - This provides for future upwards-compatible extensions. - - A server which implements the SORT and/or THREAD extensions MUST - collate strings in accordance with the requirements of I18NLEVEL=1, - as described in [IMAP-I18N], and SHOULD implement and advertise the - I18NLEVEL=1 extension. Alternatively, a server MAY implement - I18NLEVEL=2 (or higher) and comply with the rules of that level. - - Discussion: the SORT and THREAD extensions predate [IMAP-I18N] by - several years. At the time of this writing, all known server - implementations of SORT and THREAD comply with the rules of - I18NLEVEL=1, but do not necessarily advertise it. As discussed - in [IMAP-I18N] section 4.5, all server implementations should - eventually be updated to comply with the I18NLEVEL=2 extension. - - Historical note: the REFERENCES threading algorithm is based on the - [THREADING] algorithm written used in "Netscape Mail and News" - versions 2.0 through 3.0. - -2. Terminology - - 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 [KEYWORDS]. - - The word "can" (not "may") is used to refer to a possible - circumstance or situation, as opposed to an optional facility of the - protocol. - - "User" is used to refer to a human user, whereas "client" refers to - the software being run by the user. - - In examples, "C:" and "S:" indicate lines sent by the client and - server respectively. - -2.1 Base Subject - - Subject sorting and threading use the "base subject," which has - specific subject artifacts removed. Due to the complexity of these - artifacts, the formal syntax for the subject extraction rules is - ambiguous. The following procedure is followed to determine the - "base subject", using the [ABNF] formal syntax rules described in - section 5: - - (1) Convert any RFC 2047 encoded-words in the subject to - UTF-8 as described in "internationalization - considerations." Convert all tabs and continuations to - space. Convert all multiple spaces to a single space. - - (2) Remove all trailing text of the subject that matches - the subj-trailer ABNF, repeat until no more matches are - possible. - - (3) Remove all prefix text of the subject that matches the - subj-leader ABNF. - - (4) If there is prefix text of the subject that matches the - subj-blob ABNF, and removing that prefix leaves a non-empty - subj-base, then remove the prefix text. - - (5) Repeat (3) and (4) until no matches remain. - - Note: it is possible to defer step (2) until step (6), but this - requires checking for subj-trailer in step (4). - - (6) If the resulting text begins with the subj-fwd-hdr ABNF - and ends with the subj-fwd-trl ABNF, remove the - subj-fwd-hdr and subj-fwd-trl and repeat from step (2). - - (7) The resulting text is the "base subject" used in the - SORT. - - All servers and disconnected (as described in [IMAP-MODELS]) clients - MUST use exactly this algorithm to determine the "base subject". - Otherwise there is potential for a user to get inconsistent results - based on whether they are running in connected or disconnected mode. - -2.2 Sent Date - - As used in this document, the term "sent date" refers to the date and - time from the Date: header, adjusted by time zone to normalize to - UTC. For example, "31 Dec 2000 16:01:33 -0800" is equivalent to the - UTC date and time of "1 Jan 2001 00:01:33 +0000". - - If the time zone is invalid, the date and time SHOULD be treated as - UTC. If the time is also invalid, the time SHOULD be treated as - 00:00:00. If there is no valid date or time, the date and time - SHOULD be treated as 00:00:00 on the earliest possible date. - - This differs from the date-related criteria in the SEARCH command - (described in [IMAP] section 6.4.4), which use just the date and not - the time, and are not adjusted by time zone. - - If the sent date can not be determined (a Date: header is missing or - can not be parsed), the INTERNALDATE for that message is used as the - sent date. - - When comparing two sent dates that match exactly, the order in which - the two messages appear in the mailbox (that is, by sequence number) - is used as a tie-breaker to determine the order. - -3. Additional Commands - - These commands are extension to the [IMAP] base protocol. - - The section headings are intended to correspond with where they would - be located in the main document if they were part of the base - specification. - -BASE.6.4.SORT. SORT Command - - Arguments: sort program - charset specification - searching criteria (one or more) - - Data: untagged responses: SORT - - Result: OK - sort completed - NO - sort error: can't sort that charset or - criteria - BAD - command unknown or arguments invalid - - The SORT command is a variant of SEARCH with sorting semantics for - the results. Sort has two arguments before the searching criteria - argument; a parenthesized list of sort criteria, and the searching - charset. - - The charset argument is mandatory (unlike SEARCH) and indicates - the [CHARSET] of the strings that appear in the searching - criteria. The US-ASCII and UTF-8 charsets MUST be implemented. - All other charsets are optional. - - There is also a UID SORT command which returns unique identifiers - instead of message sequence numbers. Note that there are separate - searching criteria for message sequence numbers and UIDs; thus the - arguments to UID SORT are interpreted the same as in SORT. This - is analogous to the behavior of UID SEARCH, as opposed to UID - COPY, UID FETCH, or UID STORE. - - The SORT command first searches the mailbox for messages that - match the given searching criteria using the charset argument for - the interpretation of strings in the searching criteria. It then - returns the matching messages in an untagged SORT response, sorted - according to one or more sort criteria. - - Sorting is in ascending order. Earlier dates sort before later - dates; smaller sizes sort before larger sizes; and strings are - sorted according to ascending values established by their - collation algorithm (see under "Internationalization - Considerations"). - - If two or more messages exactly match according to the sorting - criteria, these messages are sorted according to the order in - which they appear in the mailbox. In other words, there is an - implicit sort criterion of "sequence number". - - When multiple sort criteria are specified, the result is sorted in - the priority order that the criteria appear. For example, - (SUBJECT DATE) will sort messages in order by their base subject - text; and for messages with the same base subject text will sort - by their sent date. - - Untagged EXPUNGE responses are not permitted while the server is - responding to a SORT command, but are permitted during a UID SORT - command. - - The defined sort criteria are as follows. Refer to the Formal - Syntax section for the precise syntactic definitions of the - arguments. If the associated RFC-822 header for a particular - criterion is absent, it is treated as the empty string. The empty - string always collates before non-empty strings. - - ARRIVAL - Internal date and time of the message. This differs from the - ON criteria in SEARCH, which uses just the internal date. - - CC - [IMAP] addr-mailbox of the first "cc" address. - - DATE - Sent date and time, as described in section 2.2. - - FROM - [IMAP] addr-mailbox of the first "From" address. - - REVERSE - Followed by another sort criterion, has the effect of that - criterion but in reverse (descending) order. - Note: REVERSE only reverses a single criterion, and does not - affect the implicit "sequence number" sort criterion if all - other criteria are identicial. Consequently, a sort of - REVERSE SUBJECT is not the same as a reverse ordering of a - SUBJECT sort. This can be avoided by use of additional - criteria, e.g. SUBJECT DATE vs. REVERSE SUBJECT REVERSE - DATE. In general, however, it's better (and faster, if the - client has a "reverse current ordering" command) to reverse - the results in the client instead of issuing a new SORT. - - SIZE - Size of the message in octets. - - SUBJECT - Base subject text. - - TO - [IMAP] addr-mailbox of the first "To" address. - - Example: C: A282 SORT (SUBJECT) UTF-8 SINCE 1-Feb-1994 - S: * SORT 2 84 882 - S: A282 OK SORT completed - C: A283 SORT (SUBJECT REVERSE DATE) UTF-8 ALL - S: * SORT 5 3 4 1 2 - S: A283 OK SORT completed - C: A284 SORT (SUBJECT) US-ASCII TEXT "not in mailbox" - S: * SORT - S: A284 OK SORT completed - -BASE.6.4.THREAD. THREAD Command - -Arguments: threading algorithm - charset specification - searching criteria (one or more) - -Data: untagged responses: THREAD - -Result: OK - thread completed - NO - thread error: can't thread that charset or - criteria - BAD - command unknown or arguments invalid - - The THREAD command is a variant of SEARCH with threading semantics - for the results. Thread has two arguments before the searching - criteria argument; a threading algorithm, and the searching - charset. - - The charset argument is mandatory (unlike SEARCH) and indicates - the [CHARSET] of the strings that appear in the searching - criteria. The US-ASCII and UTF-8 charsets MUST be implemented. - All other charsets are optional. - - There is also a UID THREAD command which returns unique - identifiers instead of message sequence numbers. Note that there - are separate searching criteria for message sequence numbers and - UIDs; thus the arguments to UID THREAD are interpreted the same as - in THREAD. This is analogous to the behavior of UID SEARCH, as - opposed to UID COPY, UID FETCH, or UID STORE. - - The THREAD command first searches the mailbox for messages that - match the given searching criteria using the charset argument for - the interpretation of strings in the searching criteria. It then - returns the matching messages in an untagged THREAD response, - threaded according to the specified threading algorithm. - - All collation is in ascending order. Earlier dates collate before - later dates and strings are collated according to ascending values - established by their collation algorithm (see under - "Internationalization Considerations"). - - Untagged EXPUNGE responses are not permitted while the server is - responding to a THREAD command, but are permitted during a UID - THREAD command. - - The defined threading algorithms are as follows: - - ORDEREDSUBJECT - - The ORDEREDSUBJECT threading algorithm is also referred to as - "poor man's threading." The searched messages are sorted by - base subject and then by the sent date. The messages are then - split into separate threads, with each thread containing - messages with the same base subject text. Finally, the threads - are sorted by the sent date of the first message in the thread. - - The first message of each thread are siblings of each other - (the "root"). The second message of a thread is the child of - the first message, and subsequent messages of the thread are - siblings of the second message and hence children of the - message at the root. Hence, there are no grandchildren in - ORDEREDSUBJECT threading. - - Children in ORDEREDSUBJECT threading do not have descendents. - Client implementations SHOULD treat descendents of a child in - a server response as being siblings of that child. - - REFERENCES - - The REFERENCES threading algorithm threads the searched - messages by grouping them together in parent/child - relationships based on which messages are replies to others. - The parent/child relationships are built using two methods: - reconstructing a message's ancestry using the references - contained within it; and checking the original (not base) - subject of a message to see if it is a reply to (or forward of) - another message. - - Note: "Message ID" in the following description refers to a - normalized form of the msg-id in [RFC-2822]. The actual - text in an RFC 2822 may use quoting, resulting in multiple - ways of expressing the same Message ID. Implementations of - the REFERENCES threading algorithm MUST normalize any msg-id - in order to avoid false non-matches due to differences in - quoting. - - For example, the msg-id - <"01KF8JCEOCBS0045PS"@xxx.yyy.com> - and the msg-id - <01KF8JCEOCBS0045PS@xxx.yyy.com> - MUST be interpreted as being the same Message ID. - - The references used for reconstructing a message's ancestry are - found using the following rules: - - If a message contains a References header line, then use the - Message IDs in the References header line as the references. - - If a message does not contain a References header line, or - the References header line does not contain any valid - Message IDs, then use the first (if any) valid Message ID - found in the In-Reply-To header line as the only reference - (parent) for this message. - - Note: Although [RFC-2822] permits multiple Message IDs in - the In-Reply-To header, in actual practice this - discipline has not been followed. For example, - In-Reply-To headers have been observed with message - addresses after the Message ID, and there are no good - heuristics for software to determine the difference. - This is not a problem with the References header however. - - If a message does not contain an In-Reply-To header line, or - the In-Reply-To header line does not contain a valid Message - ID, then the message does not have any references (NIL). - - A message is considered to be a reply or forward if the base - subject extraction rules, applied to the original subject, - remove any of the following: a subj-refwd, a "(fwd)" - subj-trailer, or a subj-fwd-hdr and subj-fwd-trl. - - The REFERENCES algorithm is significantly more complex than - ORDEREDSUBJECT and consists of six main steps. These steps are - outlined in detail below. - - (1) For each searched message: - - (A) Using the Message IDs in the message's references, link - the corresponding messages (those whose Message-ID header - line contains the given reference Message ID) together as - parent/child. Make the first reference the parent of the - second (and the second a child of the first), the second the - parent of the third (and the third a child of the second), - etc. The following rules govern the creation of these - links: - - If a message does not contain a Message-ID header line, - or the Message-ID header line does not contain a valid - Message ID, then assign a unique Message ID to this - message. - - If two or more messages have the same Message ID, then - only use that Message ID in the first (lowest sequence - number) message, and assign a unique Message ID to each - of the subsequent messages with a duplicate of that - Message ID. - - If no message can be found with a given Message ID, - create a dummy message with this ID. Use this dummy - message for all subsequent references to this ID. - - If a message already has a parent, don't change the - existing link. This is done because the References - header line may have been truncated by a MUA. As a - result, there is no guarantee that the messages - corresponding to adjacent Message IDs in the References - header line are parent and child. - - Do not create a parent/child link if creating that link - would introduce a loop. For example, before making - message A the parent of B, make sure that A is not a - descendent of B. - - Note: Message ID comparisons are case-sensitive. - - (B) Create a parent/child link between the last reference - (or NIL if there are no references) and the current message. - If the current message already has a parent, it is probably - the result of a truncated References header line, so break - the current parent/child link before creating the new - correct one. As in step 1.A, do not create the parent/child - link if creating that link would introduce a loop. Note - that if this message has no references, that it will now - have no parent. - - Note: The parent/child links created in steps 1.A and 1.B - MUST be kept consistent with one another at ALL times. - - (2) Gather together all of the messages that have no parents - and make them all children (siblings of one another) of a dummy - parent (the "root"). These messages constitute the first - (head) message of the threads created thus far. - - (3) Prune dummy messages from the thread tree. Traverse each - thread under the root, and for each message: - - If it is a dummy message with NO children, delete it. - - If it is a dummy message with children, delete it, but - promote its children to the current level. In other words, - splice them in with the dummy's siblings. - - Do not promote the children if doing so would make them - children of the root, unless there is only one child. - - (4) Sort the messages under the root (top-level siblings only) - by sent date as described in section 2.2. In the case of a - dummy message, sort its children by sent date and then use the - first child for the top-level sort. - - (5) Gather together messages under the root that have the same - base subject text. - - (A) Create a table for associating base subjects with - messages, called the subject table. - - (B) Populate the subject table with one message per each - base subject. For each child of the root: - - (i) Find the subject of this thread, by using the base - subject from either the current message or its first - child if the current message is a dummy. This is the - thread subject. - - (ii) If the thread subject is empty, skip this message. - - (iii) Look up the message associated with the thread - subject in the subject table. - - (iv) If there is no message in the subject table with the - thread subject, add the current message and the thread - subject to the subject table. - - Otherwise, if the message in the subject table is not a - dummy, AND either of the following criteria are true: - - The current message is a dummy, OR - - The message in the subject table is a reply or forward - and the current message is not. - - then replace the message in the subject table with the - current message. - - (C) Merge threads with the same thread subject. For each - child of the root: - - (i) Find the message's thread subject as in step 5.B.i - above. - - (ii) If the thread subject is empty, skip this message. - - (iii) Lookup the message associated with this thread - subject in the subject table. - - (iv) If the message in the subject table is the current - message, skip this message. - - Otherwise, merge the current message with the one in the - subject table using the following rules: - - If both messages are dummies, append the current - message's children to the children of the message in - the subject table (the children of both messages - become siblings), and then delete the current message. - - If the message in the subject table is a dummy and the - current message is not, make the current message a - child of the message in the subject table (a sibling - of its children). - - If the current message is a reply or forward and the - message in the subject table is not, make the current - message a child of the message in the subject table (a - sibling of its children). - - Otherwise, create a new dummy message and make both - the current message and the message in the subject - table children of the dummy. Then replace the message - in the subject table with the dummy message. - - Note: Subject comparisons are case-insensitive, as - described under "Internationalization - Considerations." - - (6) Traverse the messages under the root and sort each set of - siblings by sent date as described in section 2.2. Traverse - the messages in such a way that the "youngest" set of siblings - are sorted first, and the "oldest" set of siblings are sorted - last (grandchildren are sorted before children, etc). In the - case of a dummy message (which can only occur with top-level - siblings), use its first child for sorting. - - Example: C: A283 THREAD ORDEREDSUBJECT UTF-8 SINCE 5-MAR-2000 - S: * THREAD (166)(167)(168)(169)(172)(170)(171) - (173)(174 (175)(176)(178)(181)(180))(179)(177 - (183)(182)(188)(184)(185)(186)(187)(189))(190) - (191)(192)(193)(194 195)(196 (197)(198))(199) - (200 202)(201)(203)(204)(205)(206 207)(208) - S: A283 OK THREAD completed - C: A284 THREAD ORDEREDSUBJECT US-ASCII TEXT "gewp" - S: * THREAD - S: A284 OK THREAD completed - C: A285 THREAD REFERENCES UTF-8 SINCE 5-MAR-2000 - S: * THREAD (166)(167)(168)(169)(172)((170)(179)) - (171)(173)((174)(175)(176)(178)(181)(180)) - ((177)(183)(182)(188 (184)(189))(185 186)(187)) - (190)(191)(192)(193)((194)(195 196))(197 198) - (199)(200 202)(201)(203)(204)(205 206 207)(208) - S: A285 OK THREAD completed - - Note: The line breaks in the first and third server - responses are for editorial clarity and do not appear in - real THREAD responses. - -4. Additional Responses - - These responses are extensions to the [IMAP] base protocol. - - The section headings of these responses are intended to correspond - with where they would be located in the main document. - -BASE.7.2.SORT. SORT Response - - Data: zero or more numbers - - The SORT response occurs as a result of a SORT or UID SORT - command. The number(s) refer to those messages that match the - search criteria. For SORT, these are message sequence numbers; - for UID SORT, these are unique identifiers. Each number is - delimited by a space. - - Example: S: * SORT 2 3 6 - -BASE.7.2.THREAD. THREAD Response - - Data: zero or more threads - - The THREAD response occurs as a result of a THREAD or UID THREAD - command. It contains zero or more threads. A thread consists of - a parenthesized list of thread members. - - Thread members consist of zero or more message numbers, delimited - by spaces, indicating successive parent and child. This continues - until the thread splits into multiple sub-threads, at which point - the thread nests into multiple sub-threads with the first member - of each subthread being siblings at this level. There is no limit - to the nesting of threads. - - The messages numbers refer to those messages that match the search - criteria. For THREAD, these are message sequence numbers; for UID - THREAD, these are unique identifiers. - - Example: S: * THREAD (2)(3 6 (4 23)(44 7 96)) - - The first thread consists only of message 2. The second thread - consists of the messages 3 (parent) and 6 (child), after which it - splits into two subthreads; the first of which contains messages 4 - (child of 6, sibling of 44) and 23 (child of 4), and the second of - which contains messages 44 (child of 6, sibling of 4), 7 (child of - 44), and 96 (child of 7). Since some later messages are parents - of earlier messages, the messages were probably moved from some - other mailbox at different times. - - -- 2 - - -- 3 - \-- 6 - |-- 4 - | \-- 23 - | - \-- 44 - \-- 7 - \-- 96 - - Example: S: * THREAD ((3)(5)) - - In this example, 3 and 5 are siblings of a parent which does not - match the search criteria (and/or does not exist in the mailbox); - however they are members of the same thread. - -5. Formal Syntax of SORT and THREAD Commands and Responses - - The following syntax specification uses the Augmented Backus-Naur - Form (ABNF) notation as specified in [ABNF]. It also uses [ABNF] - rules defined in [IMAP]. - -sort = ["UID" SP] "SORT" SP sort-criteria SP search-criteria - -sort-criteria = "(" sort-criterion *(SP sort-criterion) ")" - -sort-criterion = ["REVERSE" SP] sort-key - -sort-key = "ARRIVAL" / "CC" / "DATE" / "FROM" / "SIZE" / - "SUBJECT" / "TO" - -thread = ["UID" SP] "THREAD" SP thread-alg SP search-criteria - -thread-alg = "ORDEREDSUBJECT" / "REFERENCES" / thread-alg-ext - -thread-alg-ext = atom - ; New algorithms MUST be registered with IANA - -search-criteria = charset 1*(SP search-key) - -charset = atom / quoted - ; CHARSET values MUST be registered with IANA - -sort-data = "SORT" *(SP nz-number) - -thread-data = "THREAD" [SP 1*thread-list] - -thread-list = "(" (thread-members / thread-nested) ")" - -thread-members = nz-number *(SP nz-number) [SP thread-nested] - -thread-nested = 2*thread-list - - The following syntax describes base subject extraction rules (2)-(6): - -subject = *subj-leader [subj-middle] *subj-trailer - -subj-refwd = ("re" / ("fw" ["d"])) *WSP [subj-blob] ":" - -subj-blob = "[" *BLOBCHAR "]" *WSP - -subj-fwd = subj-fwd-hdr subject subj-fwd-trl - -subj-fwd-hdr = "[fwd:" - -subj-fwd-trl = "]" - -subj-leader = (*subj-blob subj-refwd) / WSP - -subj-middle = *subj-blob (subj-base / subj-fwd) - ; last subj-blob is subj-base if subj-base would - ; otherwise be empty - -subj-trailer = "(fwd)" / WSP - -subj-base = NONWSP *(*WSP NONWSP) - ; can be a subj-blob - -BLOBCHAR = %x01-5a / %x5c / %x5e-ff - ; any CHAR8 except '[' and ']' - -NONWSP = %x01-08 / %x0a-1f / %x21-ff - ; any CHAR8 other than WSP - -6. Security Considerations - - The SORT and THREAD extensions do not raise any security - considerations that are not present in the base [IMAP] protocol, and - these issues are discussed in [IMAP]. Nevertheless, it is important - to remember that [IMAP] protocol transactions, including message - data, are sent in the clear over the network unless protection from - snooping is negotiated, either by the use of STARTTLS, privacy - protection is negotiated in the AUTHENTICATE command, or some other - protection mechanism. - - Although not a security consideration, it is important to recognize - that sorting by REFERENCES can lead to misleading threading trees. - For example, a message with false References: header data will cause - a thread to be incorporated into another thread. - - The process of extracting the base subject may lead to incorrect - collation if the extracted data was significant text as opposed to - a subject artifact. - -7. Internationalization Considerations - - As stated in the introduction, the rules of I18NLEVEL=1 as described - in [IMAP-I18N] MUST be followed; that is, the SORT and THREAD - extensions MUST collate strings according to the i;unicode-casemap - collation described in [UNICASEMAP]. Servers SHOULD also advertise - the I18NLEVEL=1 extension. Alternatively, a server MAY implement - I18NLEVEL=2 (or higher) and comply with the rules of that level. - - As discussed in [IMAP-I18N] section 4.5, all server implementations - should eventually be updated to support the [IMAP-I18N] I18NLEVEL=2 - extension. - - Translations of the "re" or "fw"/"fwd" tokens are not specified for - removal in the base subject extraction process. An attempt to add - such translated tokens would result in a geometrically complex, and - ultimately unimplementable, task. - - Instead, note that [RFC-2822] section 3.6.5 recommends that "re:" - (from the Latin "res", in the matter of) be used to identify a reply. - Although it is evident that, from the multiple forms of token to - identify a forwarded message, there is considerable variation found - in the wild, the variations are (still) manageable. Consequently, it - is suggested that "re:" and one of the variations of the tokens for - forward supported by the base subject extraction rules be adopted for - Internet mail messages, since doing so makes it a simple display time - task to localize the token language for the user. - -8. IANA Considerations - - [IMAP] capabilities are registered by publishing a standards track or - IESG approved experimental RFC. This document constitutes - registration of the SORT and THREAD capabilities in the [IMAP] - capabilities registry. - - This document creates a new [IMAP] threading algorithms registry, - which registers threading algorithms by publishing a standards track - or IESG approved experimental RFC. This document constitutes - registration of the ORDEREDSUBJECT and REFERENCES algorithms in that - registry. - -9. Normative References - - The following documents are normative to this document: - - [ABNF] Crocker, D. and Overell, P. "Augmented BNF - for Syntax Specifications: ABNF", RFC 5234 - January 2008 - - [CHARSET] Freed, N. and Postel, J. "IANA Character Set - Registration Procedures", RFC 2978, October - 2000. - - [IMAP] Crispin, M. "Internet Message Access Protocol - - Version 4rev1", RFC 3501, March 2003. - - [IMAP-I18N] Newman, C. and Gulbrandsen, A. "Internet - Message Access Protocol Internationalization", - Work in Progress. - - [KEYWORDS] Bradner, S. "Key words for use in RFCs to - Indicate Requirement Levels", BCP 14, RFC 2119, - March 1997. - - [RFC-2822] Resnick, P. "Internet Message Format", RFC - 2822, April 2001. - - [UNICASEMAP] Crispin, M. "i;unicode-casemap - Simple Unicode - Collation Algorithm", RFC 5051. - -10. Informative References - - The following documents are informative to this document: - - [IMAP-MODELS] Crispin, M. "Distributed Electronic Mail Models - in IMAP4", RFC 1733, December 1994. - - [THREADING] Zawinski, J. "Message Threading", - http://www.jwz.org/doc/threading.html, - 1997-2002. - -Appendices - -Author's Address - - Mark R. Crispin - Networks and Distributed Computing - University of Washington - 4545 15th Avenue NE - Seattle, WA 98105-4527 - - Phone: +1 (206) 543-5762 - - EMail: MRC@CAC.Washington.EDU - - Kenneth Murchison - Carnegie Mellon University - 5000 Forbes Avenue - Cyert Hall 285 - Pittsburgh, PA 15213 - - Phone: +1 (412) 268-2638 - Email: murch@andrew.cmu.edu - -Full Copyright Statement - - Copyright (C) The IETF Trust (2008). - - This document is subject to the rights, licenses and restrictions - contained in BCP 78, and except as set forth therein, the authors - retain all their rights. - - This document and the information contained herein are provided on an - "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS - OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND - THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS - OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF - THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED - WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - -Intellectual Property - - The IETF takes no position regarding the validity or scope of any - Intellectual Property Rights or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; nor does it represent that it has - made any independent effort to identify any such rights. Information - on the procedures with respect to rights in RFC documents can be - found in BCP 78 and BCP 79. - - Copies of IPR disclosures made to the IETF Secretariat and any - assurances of licenses to be made available, or the result of an - attempt made to obtain a general license or permission for the use of - such proprietary rights by implementers or users of this - specification can be obtained from the IETF on-line IPR repository at - http://www.ietf.org/ipr. - - The IETF invites any interested party to bring to its attention any - copyrights, patents or patent applications, or other proprietary - rights that may cover technology that may be required to implement - this standard. Please address the information to the IETF at ietf- - ipr@ietf.org. - -Acknowledgement - - Funding for the RFC Editor function is currently provided by the - Internet Society. |