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Versions: (draft-martin-sieve-notify) 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 5435

Sieve Working Group                                     A. Melnikov, Ed.
Internet-Draft                                             Isode Limited
Expires: August 8, 2006                                    B. Leiba, Ed.
                                                            W. Segmuller
                                         IBM T.J. Watson Research Center
                                                               T. Martin
                                                          Mirapoint Inc.
                                                        February 4, 2006


                     Sieve Extension: Notifications
                       draft-ietf-sieve-notify-02

Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   Users go to great lengths to be notified as quickly as possible that
   they have received new mail.  Most of these methods involve polling
   to check for new messages periodically.  A push method handled by the
   final delivery agent gives users quicker notifications and saves



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   server resources.  This document does not specify the notification
   method but is expected that using existing instant messaging
   infrastructure such as Zephyr, Jabber, or SMS messages will be
   popular.  This draft describes an extension to the Sieve mail
   filtering language that allows users to give specific rules for how
   and when notifications should be sent.

Note


Table of Contents

   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   3
   1.1  Conventions used in this document  . . . . . . . . . . . . .   3

   2.   Capability Identifier  . . . . . . . . . . . . . . . . . . .   4

   3.   Notify Action  . . . . . . . . . . . . . . . . . . . . . . .   5
   3.1  Notify Action Syntax and Semantics . . . . . . . . . . . . .   5
   3.2  Notify tag ":method" . . . . . . . . . . . . . . . . . . . .   5
   3.3  Notify tag ":priority" . . . . . . . . . . . . . . . . . . .   6
   3.4  Notify tag ":message"  . . . . . . . . . . . . . . . . . . .   6
   3.5  Examples . . . . . . . . . . . . . . . . . . . . . . . . . .   7

   4.   Test valid_notif_method  . . . . . . . . . . . . . . . . . .   9

   5.   Interactions with Other Sieve Actions  . . . . . . . . . . .  10

   6.   Security Considerations  . . . . . . . . . . . . . . . . . .  11

   7.   Extensions to ManageSieve protocol . . . . . . . . . . . . .  12

   8.   IANA Considerations  . . . . . . . . . . . . . . . . . . . .  13

   9.   Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  14

   10.  References . . . . . . . . . . . . . . . . . . . . . . . . .  15
   10.1 Normative References . . . . . . . . . . . . . . . . . . . .  15
   10.2 Non-Normative References . . . . . . . . . . . . . . . . . .  15

        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  16

        Intellectual Property and Copyright Statements . . . . . . .  17








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1.  Introduction

   This is an extension to the Sieve language defined by [Sieve] for
   providing instant notifications.  It defines the new action "notify".

   This document does not dictate the notification method used.
   Examples of possible notification methods are Zephyr and Jabber.  The
   available methods shall be site-defined.

1.1  Conventions used in this document

   Conventions for notations are as in [Sieve] section 1.1, including
   the use of [Kwds] and the use of [ABNF].

   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 [Kwds].


































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2.  Capability Identifier

   The capability string associated with the extension defined in this
   document is "notify".















































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3.  Notify Action

3.1  Notify Action Syntax and Semantics

   Usage:  notify [":method" string]
           [":priority" <"1" / "2" / "3">]
           [":message" string]

   The Notify action specifies that a notification should be sent to the
   user.  The format of the notification is implementation-defined and
   is also affected by the notification method used (see below).
   However, all content specified in the notify action SHOULD be
   included.  It is RECOMMENDED that a timestamp be included in the
   notification.  Implementations SHOULD NOT include extraneous
   information.

   If there are errors sending the notification, the Sieve interpreter
   SHOULD ignore the notification and not retry indefinitely.
   [[Barry 4: Does this really belong here?  Shouldn't we push the
   question of error recovery to the individual methods?]]

3.2  Notify tag ":method"

   The :method tag identifies the notification method that will be used;
   it is a URI.  For example, the notification method can be an SMS URI
   [SMS-URI] containing a phone number, or an XMPP [XMPP] URI containing
   a Jabber identifier [XMPP-URI].  If the :method tag is not specified,
   a default implementation-defined notification method is used, and if
   there is no default method defined, the notification is ignored.
   Implementations MUST NOT generate an error condition for lack of a
   default notification method, and execution of the script MUST
   continue.

   The supported URI values will be site-specific.  If an URI schema is
   specified that the implementation does not support, the notification
   MUST cause an error condition.  Sieve scripts can check the supported
   methods using the "valid_notif_method" test to be sure that they only
   use supported ones, to avoid such error conditions.  If the :method
   tag contains a supported URI schema, then the URI MUST be checked for
   syntactic validity.  An invalid URI syntax or an unsupported URI
   extension MUST cause an error.  An implementation MAY enforce other
   semantic restrictions on URIs -- for example an SMS URI can only
   contain phone numbers in a particular geographical region.  Violation
   of such semantic restrictions MUST also cause an error.
   [[Barry 1: "MUST" seems silly here, since the whole sentence is a
   "MAY".]]





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3.3  Notify tag ":priority"

   The :priority tag specifies the importance of the notification.  The
   :priority tag is followed by a numeric value represented as a string:
   "1" (high importance), "2" (normal importance), and "3" (low
   importance).  If no priority is given, a default priority of "2"
   SHOULD be assumed.  Some notification methods allow users to specify
   their state of activity (for example "busy" or "away from keyboard").
   If the notification method provides this information it SHOULD be
   used to selectively send notifications.  If, for example, the user
   marks herself as "busy", a notification method can require that a
   notification with a priority of "3" is not to be sent, however the
   user should be notified of a higher priority notifications.  If the
   notification method allows users to filter messages based upon
   certain parameters in the message, users SHOULD be able to filter
   based upon priority.  If the notification method does not support
   priority, then this parameter MUST be ignored.
   [[Alexey 1: Should we keep using "high", "normal" and "low"
   instead?]]
   [[Barry 3.5: Why do we call this "priority", and then explain it as
   "importance"?  Shouldn't we just call it "importance"?]]

3.4  Notify tag ":message"

   The :message tag specifies the message data to be included in the
   notification.  The entirety of the string SHOULD be sent but
   implementations MAY shorten the message for technical or aesthetic
   reasons.  If the message parameter is absent, a default message
   containing the value of the From header field and the value of the
   Subject header field will be used.  Note that the notification method
   (the ":method" tag) may affect how this information is formatted.

   The implementation of a notification method MAY modify the final
   notification text -- for example, truncating it if it exceeds a
   length limit, or modifying characters that can not be represented in
   the target character set.  Allowed modifications should be documented
   in a standards-track or informational document.

   In order to construct more complex messages the notify extension can
   be used together with the Sieve variables extension [Variables], as
   shown in the examples below.

   [[Note 2: Open issue:]] The previous version of this draft has
   defined the two variables that can't be currently represented:

      $text$     - the first text/* part





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      $text[n]$  - the first n bytes of the first text/* part



3.5  Examples


   Example 1:
       require ["notify", "fileinto", "variables"];

       if header :contains "from" "boss@example.org" {
           notify :priority "1"
               :message "This is probably very important";
           # Don't send any further notifications
           stop;
       }

       if header :contains "to" "sievemailinglist@example.org" {
           # :matches is used to get the value of the Subject header
           if header :matches "Subject" "*" {
               set "subject" "${1}";
           }

           # :matches is used to get the value of the From header
           if header :matches "From" "*" {
               set "from" "${1}";
           }

           notify :priority "3"
               :message "[SIEVE] ${from}: ${subject}";
           fileinto "INBOX.sieve";
       }



















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   Example 2:
       require ["notify", "fileinto", "variables", "envelope"];

       if header :matches "from" "*@*.example.org" {
           # :matches is used to get the MAIL FROM address
           if envelope :all :matches "from" "*" {
               set "env_from" " [really: ${1}]";
           }

           # :matches is used to get the value of the Subject header
           if header :matches "Subject" "*" {
               set "subject" "${1}";
           }

           # :matches is used to get the address from the From header
           if address :matches :all "from" "*" {
               set "from_addr" "${1}";
           }

           notify :message "${from_addr}${env_from}: ${subject}";
       }






























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4.  Test valid_notif_method

   Usage:  valid_notif_method <notification-uris: string-list>

   The "valid_notif_method" test is true if the notification methods
   listed in the notification-uris argument are supported and they are
   syntactically and semantically valid.  All of the notification
   methods must be supported and valid or the test is false.

   [[Alexey 2: The text must be clear that this test performs exactly
   the same checks as done during notify :method parameter
   verificiation.]]


   Example:  if valid_notif_method ["mailto:",
                     "http://gw.example.net/notify?test"] {
                 stop;
             }

































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5.  Interactions with Other Sieve Actions

   The notify action is compatible with all other actions, and does not
   affect the operation of other actions.  In particular, the notify
   action MUST NOT cancel the implicit keep.

   Multiple executed notify actions are allowed.
   [[Note 3: Add text about suppression of identical notifications.]]











































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6.  Security Considerations

   Security considerations are discussed in [Sieve].  Additionally,
   implementations must be careful to follow the security considerations
   of the specific notification methods.

   The notify action is potentially very dangerous.  The path the
   notification takes through the network may not be secure.  An error
   in the options string may cause the message to be transmitted to
   someone it was not intended for, or may expose information to
   eavesdroppers.

   Just because a notification is received doesn't mean it was sent by
   the Sieve implementation.  It might be possible to forge
   notifications with some notification methods.




































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7.  Extensions to ManageSieve protocol

   A ManageSieve [ManageSieve] server that supports the "notify"
   extension MUST advertise the NOTIFY capability, that has a single
   mandatory parameter.  The parameter is a string containing space
   separated list of URI schema parts for supported nofication methods.

   Example:
   S: "NOTIFY" "xmpp mailto"










































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8.  IANA Considerations

   The following template specifies the IANA registration of the
   variables Sieve extension specified in this document:

   To: iana@iana.org
   Subject: Registration of new Sieve extension
   Capability name: notify
   Capability keyword: notify
   Capability arguments: N/A
   Standards Track/IESG-approved experimental RFC number: this RFC
   Person and email address to contact for further information:
       Alexey Melnikov <Alexey.Melnikov@isode.com>

   This information should be added to the list of sieve extensions
   given on http://www.iana.org/assignments/sieve-extensions.



































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9.  Acknowledgements

   Thanks to Larry Greenfield, Sarah Robeson, Tim Showalter, Cyrus
   Daboo, Nigel Swinson, Kjetil Torgrim Homme, Michael Haardt, Mark E.
   Mallett and Ned Freed for help with this document.














































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10.  References

10.1  Normative References

   [ABNF]     Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 4234, October 2005.

   [Kwds]     Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", RFC 2119, March 1997.

   [ManageSieve]
              Martin, T. and A. Melnikov, "A Protocol for Remotely
              Managing Sieve Scripts", work in
              progress, draft-martin-managesieve, February 2006.

   [Sieve]    Guenther, P. and T. Showalter, "Sieve: An Email Filtering
              Language", work in progress, draft-ietf-sieve-3028bis,
              July 2005.

10.2  Non-Normative References

   [SMS-URI]  Wilde, E. and A. Vaha-Sipila, "URI scheme for GSM Short
              Message Service", work in progress, draft-wilde-sms-uri,
              August 2005.

   [Variables]
              Homme, K., "Sieve Extension: Variables", work in
              progress, draft-ietf-sieve-variables, October 2005.

   [XMPP]     Saint-Andre, Ed., P., "Extensible Messaging and Presence
              Protocol (XMPP): Core", RFC 3920, October 2004.

   [XMPP-URI]
              Saint-Andre, P., "Internationalized Resource Identifiers
              (IRIs) and Uniform Resource Identifiers (URIs) for the
              Extensible Messaging and Presence Protocol (XMPP)", work
              in progress, draft-saintandre-xmpp-iri, September 2005.














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Authors' Addresses

   Alexey Melnikov (editor)
   Isode Limited
   5 Castle Business Village
   36 Station Road
   Hampton, Middlesex  TW12 2BX
   UK

   Email: Alexey.Melnikov@isode.com


   Barry Leiba (editor)
   IBM T.J. Watson Research Center
   19 Skyline Drive
   Hawthorne, NY  10532
   US

   Phone: +1 914 784 7941
   Email: leiba@watson.ibm.com


   Wolfgang Segmuller
   IBM T.J. Watson Research Center
   19 Skyline Drive
   Hawthorne, NY  10532
   US

   Phone: +1 914 784 7408
   Email: werewolf@us.ibm.com


   Tim Martin
   Mirapoint Inc.
   909 Hermosa Court
   Sunnyvale, CA  94085
   US

   Phone: +1 409 720 3835
   Email: tmartin@mirapoint.com











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