draft-ietf-imapext-i18n-12.txt   draft-ietf-imapext-i18n-13.txt 
Network Working Group Chris Newman Network Working Group Chris Newman
Internet-Draft Sun Microsystems Internet-Draft Sun Microsystems
Intended Status: Proposed Standard Arnt Gulbrandsen Intended Status: Proposed Standard Arnt Gulbrandsen
Oryx Mail Systems GmhH Oryx Mail Systems GmhH
August 2007 Alexey Melnikov
Isode Limited
November 14, 2007
Internet Message Access Protocol Internationalization Internet Message Access Protocol Internationalization
draft-ietf-imapext-i18n-12.txt draft-ietf-imapext-i18n-13.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware 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 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. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
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Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
Abstract Abstract
Internet Message Access Protocol (IMAP) version 4rev1 has basic Internet Message Access Protocol (IMAP) version 4rev1 has basic
support for non-ASCII characters in mailbox names and search support for non-ASCII characters in mailbox names and search
substrings. It also supports non-ASCII message headers and content substrings. It also supports non-ASCII message headers and content
encoded as specified by Multipurpose Internet Mail Extensions encoded as specified by Multipurpose Internet Mail Extensions
(MIME). This specification defines a collection of IMAP extensions (MIME). This specification defines a collection of IMAP extensions
which improve international support including comparator negotiation
for search, sort and thread, language negotiation for international
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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. error text, and translations for namespace prefixes.
Table of Contents Table of Contents
1. Conventions Used in this Document . . . . . . . . . . . . . . 2 1. Conventions Used in this Document . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. LANGUAGE Extension . . . . . . . . . . . . . . . . . . . . . 3 3. LANGUAGE Extension . . . . . . . . . . . . . . . . . . . . . 3
3.1 LANGUAGE Extension Requirements . . . . . . . . . . . . . . . 3 3.1 LANGUAGE Extension Requirements . . . . . . . . . . . . . . . 3
3.2 LANGUAGE Command . . . . . . . . . . . . . . . . . . . . . . 4 3.2 LANGUAGE Command . . . . . . . . . . . . . . . . . . . . . . 4
3.3 LANGUAGE Response . . . . . . . . . . . . . . . . . . . . . . 6 3.3 LANGUAGE Response . . . . . . . . . . . . . . . . . . . . . . 6
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
The formal syntax use the Augmented Backus-Naur Form (ABNF) The formal syntax use the Augmented Backus-Naur Form (ABNF)
[RFC4234] notation including the core rules defined in Appendix A. [RFC4234] notation including the core rules defined in Appendix A.
The UTF8-related productions are defined in [RFC3629]. The UTF8-related productions are defined in [RFC3629].
In examples, "C:" and "S:" indicate lines sent by the client and In examples, "C:" and "S:" indicate lines sent by the client and
server respectively. If a single "C:" or "S:" label applies to server respectively. If a single "C:" or "S:" label applies to
multiple lines, then the line breaks between those lines are for multiple lines, then the line breaks between those lines are for
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editorial clarity only and are not part of the actual protocol editorial clarity only and are not part of the actual protocol
exchange. exchange.
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2. Introduction 2. Introduction
This specification defines two IMAP4rev1 [RFC3501] extensions to This specification defines two IMAP4rev1 [RFC3501] extensions to
enhance international support. These extensions can be advertised enhance international support. These extensions can be advertised
and implemented separately. and implemented separately.
The LANGUAGE extension allows the client to request a suitable The LANGUAGE extension allows the client to request a suitable
language for protocol error messages and in combination with the language for protocol error messages and in combination with the
NAMESPACE extension [RFC2342] enables namespace translations. NAMESPACE extension [RFC2342] enables namespace translations.
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IMAP servers that support this extension MUST list the keyword IMAP servers that support this extension MUST list the keyword
LANGUAGE in their CAPABILITY response as well as in the greeting LANGUAGE in their CAPABILITY response as well as in the greeting
CAPABILITY data. CAPABILITY data.
A server that advertises this extension MUST use the language "i- A server that advertises this extension MUST use the language "i-
default" as described in [RFC2277] as its default language until default" as described in [RFC2277] as its default language until
another supported language is negotiated by the client. A server another supported language is negotiated by the client. A server
MUST include "i-default" as one of its supported languages. MUST include "i-default" as one of its supported languages.
Clients and servers that support this extension MUST also support Clients and servers that support this extension MUST also support
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the NAMESPACE extension [RFC2342]. the NAMESPACE extension [RFC2342].
The LANGUAGE command is valid in all states. Clients are urged to The LANGUAGE command is valid in all states. Clients are urged to
issue LANGUAGE before authentication, since some servers send issue LANGUAGE before authentication, since some servers send
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valuable user information as part of authentication (e.g. "password valuable user information as part of authentication (e.g. "password
is correct, but expired"). is correct, but expired").
3.2 LANGUAGE Command 3.2 LANGUAGE Command
Arguments: Optional language range arguments. Arguments: Optional language range arguments.
Response: A possible LANGUAGE response (see section 3.3). Response: A possible LANGUAGE response (see section 3.3).
A possible NAMESPACE response (see section 3.4). A possible NAMESPACE response (see section 3.4).
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send an untagged LANGUAGE response indicating the language selected. send an untagged LANGUAGE response indicating the language selected.
If there aren't any arguments, the server SHOULD send an untagged If there aren't any arguments, the server SHOULD send an untagged
LANGUAGE response listing the languages it supports. If the server LANGUAGE response listing the languages it supports. If the server
is unable to enumerate the list of languages it supports it MAY is unable to enumerate the list of languages it supports it MAY
return a tagged NO response to the enumeration request. return a tagged NO response to the enumeration request.
< The server defaults to using English i-default responses until < The server defaults to using English i-default responses until
the user explicitly changes the language. > the user explicitly changes the language. >
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C: A001 LOGIN KAREN PASSWORD C: A001 LOGIN KAREN PASSWORD
S: A001 OK LOGIN completed S: A001 OK LOGIN completed
< Client requested MUL language, which no server supports. > < Client requested MUL language, which no server supports. >
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C: A002 LANGUAGE MUL C: A002 LANGUAGE MUL
S: A002 NO Unsupported language MUL S: A002 NO Unsupported language MUL
< A LANGUAGE command with no arguments is a request to enumerate < A LANGUAGE command with no arguments is a request to enumerate
the list of languages the server supports. > the list of languages the server supports. >
C: A003 LANGUAGE C: A003 LANGUAGE
S: * LANGUAGE (EN DE IT i-default) S: * LANGUAGE (EN DE IT i-default)
S: A003 OK Supported languages have been enumerated S: A003 OK Supported languages have been enumerated
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S: * LANGUAGE (DE-IT) S: * LANGUAGE (DE-IT)
S: * NAMESPACE (("" "/"))(("Other Users/" "/" "TRANSLATION" S: * NAMESPACE (("" "/"))(("Other Users/" "/" "TRANSLATION"
("Andere Ben&APw-tzer/"))) (("Public Folders/" "/" ("Andere Ben&APw-tzer/"))) (("Public Folders/" "/"
"TRANSLATION" ("Gemeinsame Mailboxen/"))) "TRANSLATION" ("Gemeinsame Mailboxen/")))
S: D002 OK Sprachwechsel durch LANGUAGE-Befehl ausgefuehrt S: D002 OK Sprachwechsel durch LANGUAGE-Befehl ausgefuehrt
C: D003 LANGUAGE "default" C: D003 LANGUAGE "default"
S: * LANGUAGE (DE) S: * LANGUAGE (DE)
S: D003 OK Sprachwechsel durch LANGUAGE-Befehl ausgefuehrt S: D003 OK Sprachwechsel durch LANGUAGE-Befehl ausgefuehrt
< Server does not speak French, but does speak English. User < Server does not speak French, but does speak English. User
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speaks Canadian French and Canadian English. > speaks Canadian French and Canadian English. >
C: E001 LANGUAGE FR-CA EN-CA C: E001 LANGUAGE FR-CA EN-CA
S: * LANGUAGE (EN) S: * LANGUAGE (EN)
S: E001 OK Now speaking English S: E001 OK Now speaking English
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3.3 LANGUAGE Response 3.3 LANGUAGE Response
Contents: A list of one or more language tags. Contents: A list of one or more language tags.
The LANGUAGE response occurs as a result of a LANGUAGE command. A The LANGUAGE response occurs as a result of a LANGUAGE command. A
LANGUAGE response with a list containing a single language tag LANGUAGE response with a list containing a single language tag
indicates that the server is now using that language. A LANGUAGE indicates that the server is now using that language. A LANGUAGE
response with a list containing multiple language tags indicates the response with a list containing multiple language tags indicates the
server is communicating a list of available languages to the client, server is communicating a list of available languages to the client,
and no change in the active language has been made. and no change in the active language has been made.
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translation of them that can be presented to the user. translation of them that can be presented to the user.
C: A001 LANGUAGE DE-IT C: A001 LANGUAGE DE-IT
S: * NAMESPACE (("" "/")) (("Other Users/" "/" "TRANSLATION" S: * NAMESPACE (("" "/")) (("Other Users/" "/" "TRANSLATION"
("Andere Ben&APw-tzer/"))) (("Public Folders/" "/" ("Andere Ben&APw-tzer/"))) (("Public Folders/" "/"
"TRANSLATION" ("Gemeinsame Mailboxen/"))) "TRANSLATION" ("Gemeinsame Mailboxen/")))
S: A001 OK LANGUAGE-Befehl ausgefuehrt S: A001 OK LANGUAGE-Befehl ausgefuehrt
3.5 Formal Syntax 3.5 Formal Syntax
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The following syntax specification inherits ABNF [RFC4234] rules The following syntax specification inherits ABNF [RFC4234] rules
from IMAP4rev1 [RFC3501], IMAP4 Namespace [RFC2342], Tags for the from IMAP4rev1 [RFC3501], IMAP4 Namespace [RFC2342], Tags for the
Identifying Languages [RFC4646], UTF-8 [RFC3629] and Collected Identifying Languages [RFC4646], UTF-8 [RFC3629] and Collected
Extensions to IMAP4 ABNF [RFC4466]. Extensions to IMAP4 ABNF [RFC4466].
command-any =/ language-cmd command-any =/ language-cmd
; LANGUAGE command is valid in all states ; LANGUAGE command is valid in all states
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language-cmd = "LANGUAGE" *(SP lang-range-quoted) language-cmd = "LANGUAGE" *(SP lang-range-quoted)
response-payload =/ language-data response-payload =/ language-data
language-data = "LANGUAGE" SP "(" lang-tag-quoted *(SP language-data = "LANGUAGE" SP "(" lang-tag-quoted *(SP
lang-tag-quoted) ")" lang-tag-quoted) ")"
namespace-trans = SP DQUOTE "TRANSLATION" DQUOTE SP "(" string ")" namespace-trans = SP DQUOTE "TRANSLATION" DQUOTE SP "(" string ")"
; the string is encoded in Modified UTF-7. ; the string is encoded in Modified UTF-7.
; this is a subset of the syntax permitted by ; this is a subset of the syntax permitted by
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4. COMPARATOR Extension 4. COMPARATOR Extension
IMAP4rev1 [RFC3501] includes the SEARCH command which can be used to IMAP4rev1 [RFC3501] includes the SEARCH command which can be used to
locate messages matching criteria including human-readable text. locate messages matching criteria including human-readable text.
The SORT extension [SORT] to IMAP allows the client to ask the The SORT extension [SORT] to IMAP allows the client to ask the
server to determine the order of messages based on criteria server to determine the order of messages based on criteria
including human-readable text. These mechanisms require the ability including human-readable text. These mechanisms require the ability
to support non-English search and sort functions. to support non-English search and sort functions.
This section defines an IMAP extension to negotiate use of This section defines an IMAP extension to negotiate use of
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comparators [RFC4790] to internationalize IMAP SEARCH, SORT and comparators [RFC4790] to internationalize IMAP SEARCH, SORT and
THREAD. The IMAP extension consists of a new command to determine THREAD. The IMAP extension consists of a new command to determine
or change the active comparator and a new response to indicate the or change the active comparator and a new response to indicate the
active comparator and possibly other available comparators. active comparator and possibly other available comparators.
The term "default comparator" refers to the comparator which is used The term "default comparator" refers to the comparator which is used
by SEARCH and SORT absent any negotiation using the COMPARATOR by SEARCH and SORT absent any negotiation using the COMPARATOR
command. The term "active comparator" refers to the comparator command. The term "active comparator" refers to the comparator
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which will be used within a session e.g. by SEARCH and SORT. The which will be used within a session e.g. by SEARCH and SORT. The
COMPARATOR command is used to change the active comparator. COMPARATOR command is used to change the active comparator.
The active comparator applies to the following SEARCH keys: "BCC", The active comparator applies to the following SEARCH keys: "BCC",
"BODY", "CC", "FROM", "SUBJECT", "TEXT", "TO" and "HEADER". If the "BODY", "CC", "FROM", "SUBJECT", "TEXT", "TO" and "HEADER". If the
server also advertises the "SORT" extension, then the active server also advertises the "SORT" extension, then the active
comparator applies to the following SORT keys: "CC", "FROM", comparator applies to the following SORT keys: "CC", "FROM",
"SUBJECT" and "TO". If the server advertises THREAD=ORDEREDSUBJECT, "SUBJECT" and "TO". If the server advertises THREAD=ORDEREDSUBJECT,
then the active comparator applies to the ORDEREDSUBJECT threading then the active comparator applies to the ORDEREDSUBJECT threading
algorithm. If the server advertises THREAD=REFERENCES, then the algorithm. If the server advertises THREAD=REFERENCES, then the
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For SORT and THREAD, the pre-processing necessary to extract the For SORT and THREAD, the pre-processing necessary to extract the
base subject text from a Subject header occurs prior to the base subject text from a Subject header occurs prior to the
application of a comparator. application of a comparator.
4.1 COMPARATOR Extension Requirements 4.1 COMPARATOR Extension Requirements
IMAP servers that support this extension MUST list the keyword IMAP servers that support this extension MUST list the keyword
COMPARATOR in their CAPABILITY data once IMAP enters authenticated COMPARATOR in their CAPABILITY data once IMAP enters authenticated
state, and MAY list that keyword in other states. state, and MAY list that keyword in other states.
A server that advertises this extension MUST implement the i;ascii- A server that advertises this extension MUST implement the
casemap and i;octet comparators, as defined in [RFC4790]. A server i;unicode-casemap comparator, as defined in [UCM]. It MAY implement
intended to be deployed globally MUST implement the i;unicode- other comparators from the IANA registry established by [RFC4790].
casemap comparator, as defined in [UCM].
A server that advertises this extension SHOULD use i;ascii-casemap A server that advertises this extension SHOULD use i;unicode-casemap
as the default comparator. The selection of the default comparator as the default comparator. The selection of the default comparator
MAY be adjustable by the server administrator, and MAY be sensitive MAY be adjustable by the server administrator, and MAY be sensitive
to the current user. Once the IMAP connection enters authenticated to the current user. Once the IMAP connection enters authenticated
state, the default comparator MUST remain static for the remainder state, the default comparator MUST remain static for the remainder
of that connection. of that connection.
A server that advertises this extension MUST support UTF-8 as a A server that advertises this extension MUST support UTF-8 as a
SEARCH charset. SEARCH charset.
The COMPARATOR command is valid in authenticated and selected The COMPARATOR command is valid in authenticated and selected
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states. states.
Note that since SEARCH uses the substring operation, IMAP servers Note that since SEARCH uses the substring operation, IMAP servers
can only implement collations that offer the substring operation can only implement collations that offer the substring operation
(see [RFC4790 section 4.2.2). Since SORT uses ordering operation (see [RFC4790 section 4.2.2). Since SORT uses ordering operation
(and by implication equality), IMAP servers which advertise the SORT (and by implication equality), IMAP servers which advertise the SORT
extension can only implement collations that offer all three extension can only implement collations that offer all three
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operations (see [RFC4790] sections 4.2.2-4). operations (see [RFC4790] sections 4.2.2-4).
If the active collation does not provide the operations needed by an If the active collation does not provide the operations needed by an
IMAP command, the server MUST respond with a tagged BAD. IMAP command, the server MUST respond with a tagged BAD.
4.2 Comparators and Character Encodings 4.2 Comparators and Character Encodings
When SEARCH, SORT, THREAD or another command needs to perform RFC 3501, section 6.4.4 says:
collation operations on messages (or on the command's arguments),
the server MUST remove MIME encoding (see [RFC2047] for headers and
[RFC2045] for bodyparts) and convert character encodings compatibly
before doing the collation operation.
Strings encoded using unknown character encodings should sort In all search keys that use strings, a message matches
together with invalid input (as defined by the active collation) for the key if the string is a substring of the field. The
the SORT and THREAD commands. 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
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]).
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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 that fail
step (b) are collated (after applying step (a)) using the
i;octet comparator (see [RFC4790]). All strings successfully
converted by step (b) are collated using the active comparator.
The resulting sorted list is produced by appending all collated
"failed" strings after all strings collated using the active
comparator.
<<Add an example>>
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).
4.3 COMPARATOR Command 4.3 COMPARATOR Command
Arguments: Optional comparator order arguments. Arguments: Optional comparator order arguments.
Response: A possible COMPARATOR response (see Section 4.4). Response: A possible COMPARATOR response (see Section 4.4).
Result: OK - Command completed Result: OK - Command completed
NO - No matching comparator found NO - No matching comparator found
BAD - arguments invalid BAD - arguments invalid
The COMPARATOR command is used to determine or change the active The COMPARATOR command is used to determine or change the active
comparator. When issued with no arguments, it results in a comparator. When issued with no arguments, it results in a
COMPARATOR response indicating the currently active comparator. COMPARATOR response indicating the currently active comparator.
When issued with one or more comparator argument, it changes the When issued with one or more comparator argument, it changes the
active comparator as directed. (If more than one installed active comparator as directed. (If more than one installed
comparator is matched by an argument, the first argument wins.) The comparator is matched by an argument, the first argument wins.) The
COMPARATOR response lists all matching comparators if more than one COMPARATOR response lists all matching comparators if more than one
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matches the specified patterns. matches the specified patterns.
The argument "default" refers to the server's default comparator. The argument "default" refers to the server's default comparator.
Otherwise each argument is an collation specification as defined in Otherwise each argument is an collation specification as defined in
the Internet Application Protocol Comparator Registry [RFC4790]. the Internet Application Protocol Comparator Registry [RFC4790].
< The client requests activating a Czech comparator if possible, < The client requests activating a Czech comparator if possible,
or else a generic international comparator which it considers or else a generic international comparator which it considers
suitable for Czech. The server picks the first supported suitable for Czech. The server picks the first supported
comparator. > comparator. >
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C: A001 COMPARATOR "cz;*" i;basic C: A001 COMPARATOR "cz;*" i;basic
S: * COMPARATOR i;basic S: * COMPARATOR i;basic
S: A001 OK Will use i;basic for collation S: A001 OK Will use i;basic for collation
4.4 COMPARATOR Response 4.4 COMPARATOR Response
Contents: The active comparator. Contents: The active comparator.
An optional list of available matching comparators An optional list of available matching comparators
The COMPARATOR response occurs as a result of a COMPARATOR command. The COMPARATOR response occurs as a result of a COMPARATOR command.
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response-payload =/ comparator-data response-payload =/ comparator-data
comparator-data = "COMPARATOR" SP comp-sel-quoted [SP "(" comparator-data = "COMPARATOR" SP comp-sel-quoted [SP "("
comp-id-quoted *(SP comp-id-quoted) ")"] comp-id-quoted *(SP comp-id-quoted) ")"]
comp-id-quoted = astring comp-id-quoted = astring
; Once any literal wrapper or quoting is removed, this ; Once any literal wrapper or quoting is removed, this
; follows the collation-id rule from [RFC4790] ; follows the collation-id rule from [RFC4790]
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comp-order-quoted = astring comp-order-quoted = astring
; Once any literal wrapper or quoting is removed, this ; Once any literal wrapper or quoting is removed, this
; follows the collation-order rule from [RFC4790] ; follows the collation-order rule from [RFC4790]
comp-sel-quoted = astring comp-sel-quoted = astring
; Once any literal wrapper or quoting is removed, this ; Once any literal wrapper or quoting is removed, this
; follows the collation-selected rule from [RFC4790] ; follows the collation-selected rule from [RFC4790]
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An IMAP server that implements the i;unicode-casemap comparator
[UCM] and satisfies all requirements specified in sections 4, 4.1
and 4.2 of this document, but doesn't implement the COMPARATOR
command and response, SHOULD advertise the UNICASEMAP capability in
the CAPABILITY response.
5. Other IMAP Internationalization Issues 5. Other IMAP Internationalization Issues
The following sections provide an overview of various other IMAP The following sections provide an overview of various other IMAP
internationalization issues. These issues are not resolved by this internationalization issues. These issues are not resolved by this
specification, but could be resolved by other standards work, such specification, but could be resolved by other standards work, such
as that being done by the EAI group (see [IMAP-EAI]). as that being done by the EAI group (see [IMAP-EAI]).
5.1 Unicode Userids and Passwords 5.1 Unicode Userids and Passwords
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When AUTHENTICATE is used, some servers may support userids and When AUTHENTICATE is used, some servers may support userids and
passwords in Unicode [RFC3490] since SASL (see [RFC4422]) allows passwords in Unicode [RFC3490] since SASL (see [RFC4422]) allows
that. However, such userids cannot be used as part of email that. However, such userids cannot be used as part of email
addresses. addresses.
5.2 UTF-8 Mailbox Names 5.2 UTF-8 Mailbox Names
The modified UTF-7 mailbox naming convention described in section 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 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, quo in 1996 when modified UTF-7 was first specified. At that time,
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there was widespread unofficial use of local character sets such as there was widespread unofficial use of local character sets such as
ISO-8859-1 and Shift-JIS for non-ASCII mailbox names, with resultant ISO-8859-1 and Shift-JIS for non-ASCII mailbox names, with resultant
non-interoperability. non-interoperability.
The requirements in section 5.1 of RFC 3501 are very important if The requirements in section 5.1 of RFC 3501 are very important if
we're ever going to be able to deploy UTF-8 mailbox names. Servers we're ever going to be able to deploy UTF-8 mailbox names. Servers
are encouraged to enforce them. are encouraged to enforce them.
5.3 UTF-8 Domains, Addresses and Mail Headers 5.3 UTF-8 Domains, Addresses and Mail Headers
There is now an IETF standard for Internationalizing Domain Names in There is now an IETF standard for Internationalizing Domain Names in
Applications [RFC3490]. While IMAP clients are free to support this Applications [RFC3490]. While IMAP clients are free to support this
standard, an argument can be made that it would be helpful to simple standard, an argument can be made that it would be helpful to simple
clients if the IMAP server could perform this conversion (the same clients if the IMAP server could perform this conversion (the same
argument would apply to MIME header encoding [RFC2047]). However, argument would apply to MIME header encoding [RFC2047]). However,
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it would be unwise to move forward with such work until the work in it would be unwise to move forward with such work until the work in
progress to define the format of international email addresses is progress to define the format of international email addresses is
complete. complete.
6. IANA Considerations 6. IANA Considerations
The IANA is requested to add LANGUAGE and COMPARATOR to the IMAP4 The IANA is requested to add LANGUAGE, COMPARATOR and UNICASEMAP to
Capabilities Registry. [Note to IANA: the IMAP4 Capabilities Registry. [Note to IANA:
http://www.iana.org/assignments/imap4-capabilities] http://www.iana.org/assignments/imap4-capabilities]
7. Security Considerations 7. Security Considerations
The LANGUAGE extension makes a new command available in "Not The LANGUAGE extension makes a new command available in "Not
Authenticated" state in IMAP. Some IMAP implementations run with Authenticated" state in IMAP. Some IMAP implementations run with
root privilege when the server is in "Not Authenticated" state and root privilege when the server is in "Not Authenticated" state and
do not revoke that privilege until after authentication is complete. do not revoke that privilege until after authentication is complete.
Such implementations are particularly vulnerable to buffer overflow Such implementations are particularly vulnerable to buffer overflow
security errors at this stage and need to implement parsing of this security errors at this stage and need to implement parsing of this
skipping to change at page 12, line 37 skipping to change at page 14, line 4
A LANGUAGE command issued prior to activation of a security layer is A LANGUAGE command issued prior to activation of a security layer is
subject to an active attack which suppresses or modifies the subject to an active attack which suppresses or modifies the
negotiation and thus makes STARTTLS or authentication error messages negotiation and thus makes STARTTLS or authentication error messages
more difficult to interpret. This is not a new attack as the error more difficult to interpret. This is not a new attack as the error
messages themselves are subject to active attack. Clients MUST re- messages themselves are subject to active attack. Clients MUST re-
issue the LANGUAGE command once a security layer is active, so this issue the LANGUAGE command once a security layer is active, so this
does not impact subsequent protocol operations. does not impact subsequent protocol operations.
Both the LANGUAGE and COMPARATOR extensions use the UTF-8 charset, Both the LANGUAGE and COMPARATOR extensions use the UTF-8 charset,
thus the security considerations for UTF-8 [RFC3629] are relevent. thus the security considerations for UTF-8 [RFC3629] are relevent.
Internet-draft November 2007
However, neither uses UTF-8 for identifiers so the most serious However, neither uses UTF-8 for identifiers so the most serious
concerns do not apply. concerns do not apply.
8. Acknowledgements 8. Acknowledgements
The LANGUAGE extension is based on a previous Internet draft by Mike The LANGUAGE extension is based on a previous Internet draft by Mike
Gahrns and Alexey Melnikov, a substantial portion of the text in Gahrns and Alexey Melnikov, a substantial portion of the text in
that section was written by them. Many people have participated in that section was written by them. Many people have participated in
discussions about an IMAP Language extension in the various fora of discussions about an IMAP Language extension in the various fora of
the IETF and Internet working groups, so any list of contributors is the IETF and Internet working groups, so any list of contributors is
bound to be incomplete. However, the authors would like to thank bound to be incomplete. However, the authors would like to thank
Andrew McCown for early work on the original proposal, John Myers Andrew McCown for early work on the original proposal, John Myers
for suggestions regarding the namespace issue, along with Jutta for suggestions regarding the namespace issue, along with Jutta
Degener, Mark Crispin, Mark Pustilnik, Larry Osterman, Cyrus Daboo Degener, Mark Crispin, Mark Pustilnik, Larry Osterman, Cyrus Daboo
and Martin Duerst for their many suggestions that have been and Martin Duerst for their many suggestions that have been
Internet-draft August 2007
incorporated into this document. incorporated into this document.
Initial discussion of the COMPARATOR extension involved input from Initial discussion of the COMPARATOR extension involved input from
Mark Crispin and other participants of the IMAP Extensions WG. Mark Crispin and other participants of the IMAP Extensions WG.
9. Relevant Standards for i18n IMAP Implementations 9. Relevant Standards for i18n IMAP Implementations
This is a non-normative list of standards to consider when This is a non-normative list of standards to consider when
implementing i18n aware IMAP software. implementing i18n aware IMAP software.
skipping to change at page 13, line 37 skipping to change at page 15, line 5
automatically combine multipart parameters when generating the automatically combine multipart parameters when generating the
BODYSTRUCTURE. There is also some deployed non-standard use of BODYSTRUCTURE. There is also some deployed non-standard use of
MIME header encoding inside double-quotes for filenames. MIME header encoding inside double-quotes for filenames.
o IDNA [RFC3490] and punycode [RFC3492] for domain names o IDNA [RFC3490] and punycode [RFC3492] for domain names
(presently only relevant to IMAP clients). (presently only relevant to IMAP clients).
o The UTF-8 charset [RFC3629]. o The UTF-8 charset [RFC3629].
o The IETF policy on Character Sets and Languages [RFC2277]. o The IETF policy on Character Sets and Languages [RFC2277].
Normative References Normative References
Internet-draft November 2007
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2277] Alvestrand, "IETF Policy on Character Sets and [RFC2277] Alvestrand, "IETF Policy on Character Sets and
Languages", BCP 18, RFC 2277, January 1998. Languages", BCP 18, RFC 2277, January 1998.
[RFC2342] Gahrns, Newman, "IMAP4 Namespace", RFC 2342, May 1998. [RFC2342] Gahrns, Newman, "IMAP4 Namespace", RFC 2342, May 1998.
[RFC3501] Crispin, "INTERNET MESSAGE ACCESS PROTOCOL - VERSION [RFC3501] Crispin, "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 3501, March 2003. 4rev1", RFC 3501, March 2003.
[RFC3629] Yergeau, "UTF-8, a transformation format of ISO 10646", [RFC3629] Yergeau, "UTF-8, a transformation format of ISO 10646",
STD 63, RFC 3629, November 2003. STD 63, RFC 3629, November 2003.
[RFC4234] Crocker, Overell, "Augmented BNF for Syntax [RFC4234] Crocker, Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 4234, Brandenburg Specifications: ABNF", RFC 4234, Brandenburg
Internet-draft August 2007
Internetworking, Demon Internet Ltd, October 2005. Internetworking, Demon Internet Ltd, October 2005.
[RFC4422] Melnikov, Zeilenga, "Simple Authentication and Security [RFC4422] Melnikov, Zeilenga, "Simple Authentication and Security
Layer (SASL)", RFC 4422, June 2006. Layer (SASL)", RFC 4422, June 2006.
[RFC4466] Melnikov, Daboo, "Collected Extensions to IMAP4 ABNF", [RFC4466] Melnikov, Daboo, "Collected Extensions to IMAP4 ABNF",
RFC 4466, Isode Ltd., April 2006. RFC 4466, Isode Ltd., April 2006.
[RFC4646] Philips, Davis, "Tags for Identifying Languages", BCP 47, [RFC4646] Philips, Davis, "Tags for Identifying Languages", BCP 47,
RFC 4646, September 2006. RFC 4646, September 2006.
[RFC4647] Philips, Davis, "Matching of Language Tags", BCP 47, RFC [RFC4647] Philips, Davis, "Matching of Language Tags", BCP 47, RFC
4647, September 2006. 4647, September 2006.
[RFC4790] Newman, Duerst, Gulbrandsen, "Internet Application [RFC4790] Newman, Duerst, Gulbrandsen, "Internet Application
Protocol Comparator Registry", RFC 4790, February 2007 Protocol Comparator Registry", RFC 4790, February 2007
[SORT] Crispin, M. and K. Murchison, "INTERNET MESSAGE ACCESS [SORT] Crispin, M. and K. Murchison, "INTERNET MESSAGE ACCESS
PROTOCOL - SORT AND THREAD EXTENSION", draft-ietf- PROTOCOL - SORT AND THREAD EXTENSION", draft-ietf-
imapext-sort-18 (work in progress), November 2006. imapext-sort-19 (work in progress), November 2006.
[UCM] Crispin, "i;unicode-casemap - Simple Unicode Collation [UCM] Crispin, "i;unicode-casemap - Simple Unicode Collation
Algorithm", draft-crispin-collation-unicasemap-04.txt, Algorithm", RFC 5051, October 2007.
May 2007.
Informative References
[RFC2045] Freed, Borenstein, "Multipurpose Internet Mail Extensions [RFC2045] Freed, Borenstein, "Multipurpose Internet Mail Extensions
(MIME) Part One: Format of Internet Message Bodies", RFC (MIME) Part One: Format of Internet Message Bodies", RFC
2045, November 1996. 2045, November 1996.
[RFC2047] Moore, "MIME (Multipurpose Internet Mail Extensions) Part [RFC2047] Moore, "MIME (Multipurpose Internet Mail Extensions) Part
Three: Message Header Extensions for Non-ASCII Text", RFC Three: Message Header Extensions for Non-ASCII Text", RFC
2047, November 1996. 2047, November 1996.
Internet-draft November 2007
Informative References
[RFC2231] Freed, Moore, "MIME Parameter Value and Encoded Word [RFC2231] Freed, Moore, "MIME Parameter Value and Encoded Word
Extensions: Character Sets, Languages, and Extensions: Character Sets, Languages, and
Continuations", RFC 2231, November 1997. Continuations", RFC 2231, November 1997.
[RFC3490] Faltstrom, Hoffman, Costello, "Internationalizing Domain [RFC3490] Faltstrom, Hoffman, Costello, "Internationalizing Domain
Names in Applications (IDNA)", RFC 3490, March 2003. Names in Applications (IDNA)", RFC 3490, March 2003.
[RFC3492] Costello, "Punycode: A Bootstring encoding of Unicode for [RFC3492] Costello, "Punycode: A Bootstring encoding of Unicode for
Internationalized Domain Names in Applications (IDNA)", Internationalized Domain Names in Applications (IDNA)",
RFC 3492, March 2003. RFC 3492, March 2003.
[METADATA] Daboo, C., "IMAP METADATA Extension", draft-daboo-imap- [METADATA] Daboo, C., "IMAP METADATA Extension", draft-daboo-imap-
annotatemore-11 (work in progress), November 2006.
Internet-draft August 2007
annotatemore-10 (work in progress), November 2006.
[IMAP-EAI] Resnick, Newman, "IMAP Support for UTF-8", draft-ietf- [IMAP-EAI] Resnick, Newman, "IMAP Support for UTF-8", draft-ietf-
eai-imap-utf8 (work in progress), May 2006. eai-imap-utf8 (work in progress), May 2006.
Authors' Addresses Authors' Addresses
Chris Newman Chris Newman
Sun Microsystems Sun Microsystems
3401 Centrelake Dr., Suite 410 3401 Centrelake Dr., Suite 410
Ontario, CA 91761 Ontario, CA 91761
skipping to change at page 16, line 5 skipping to change at page 16, line 46
Arnt Gulbrandsen Arnt Gulbrandsen
Oryx Mail Systems GmbH Oryx Mail Systems GmbH
Schweppermannstr. 8 Schweppermannstr. 8
D-81671 Muenchen D-81671 Muenchen
Germany Germany
Email: arnt@oryx.com Email: arnt@oryx.com
Fax: +49 89 4502 9758 Fax: +49 89 4502 9758
Internet-draft August 2007 Alexey Melnikov
Isode Limited
5 Castle Business Village, 36 Station Road,
Hampton, Middlesex, TW12 2BX, UK
Internet-draft November 2007
Email: Alexey.Melnikov@isode.com
Internet-draft November 2007
Intellectual Property Statement Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed Intellectual Property Rights or other rights that might be claimed
to pertain to the implementation or use of the technology described to pertain to the implementation or use of the technology described
in this document or the extent to which any license under such in this document or the extent to which any license under such
rights might or might not be available; nor does it represent that rights might or might not be available; nor does it represent that
it has made any independent effort to identify any such rights. it has made any independent effort to identify any such rights.
Information on the procedures with respect to rights in RFC Information on the procedures with respect to rights in RFC
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