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+Network Working Group                                       W. Segmuller
+Request for Comment: 3431                IBM T.J. Watson Research Center
+Category: Standards Track                                  December 2002
+
+
+                   Sieve Extension: Relational Tests
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2002).  All Rights Reserved.
+
+Abstract
+
+   This document describes the RELATIONAL extension to the Sieve mail
+   filtering language defined in RFC 3028.  This extension extends
+   existing conditional tests in Sieve to allow relational operators.
+   In addition to testing their content, it also allows for testing of
+   the number of entities in header and envelope fields.
+
+1 Introduction
+
+   Sieve [SIEVE] is a language for filtering e-mail messages at the time
+   of final delivery.  It is designed to be implementable on either a
+   mail client or mail server.  It is meant to be extensible, simple,
+   and independent of access protocol, mail architecture, and operating
+   system.  It is suitable for running on a mail server where users may
+   not be allowed to execute arbitrary programs, such as on black box
+   Internet Messages Access Protocol (IMAP) servers, as it has no
+   variables, loops, nor the ability to shell out to external programs.
+
+   The RELATIONAL extension provides relational operators on the
+   address, envelope, and header tests.  This extension also provides a
+   way of counting the entities in a message header or address field.
+
+   With this extension, the sieve script may now determine if a field is
+   greater than or less than a value instead of just equivalent.  One
+   use is for the x-priority field: move messages with a priority
+   greater than 3 to the "work on later" folder.  Mail could also be
+   sorted by the from address.  Those userids that start with 'a'-'m' go
+   to one folder, and the rest go to another folder.
+
+
+
+Segmuller                   Standards Track                     [Page 1]
+
+RFC 3431           Sieve Extension: Relational Tests       December 2002
+
+
+   The sieve script can also determine the number of fields in the
+   header, or the number of addresses in a recipient field.  For
+   example:  are there more than 5 addresses in the to and cc fields.
+
+2 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 BCP 14, RFC 2119.
+
+   Conventions for notations are as in [SIEVE] section 1.1, including
+   the use of [KEYWORDS] and "Syntax:" label for the definition of
+   action and tagged arguments syntax, and the use of [ABNF].
+
+   The capability string associated with extension defined in this
+   document is "relational".
+
+3 Comparators
+
+   This document does not define any comparators or exempt any
+   comparators from the require clause.  Any comparator used, other than
+   "i;octet" and "i;ascii-casemap", MUST be declared a require clause as
+   defined in [SIEVE].
+
+   The "i;ascii-numeric" comparator, as defined in [ACAP], MUST be
+   supported for any implementation of this extension.  The comparator
+   "i;ascii-numeric" MUST support at least 32 bit unsigned integers.
+
+   Larger integers MAY be supported.  Note: the "i;ascii-numeric"
+   comparator does not support negative numbers.
+
+4 Match Type
+
+   This document defines two new match types.  They are the VALUE match
+   type and the COUNT match type.
+
+     The syntax is:
+
+        MATCH-TYPE =/ COUNT / VALUE
+
+        COUNT = ":count" relational-match
+
+        VALUE = ":value" relational-match
+
+        relational-match = DQUOTE ( "gt" / "ge" / "lt"
+                                    / "le" / "eq" / "ne" ) DQUOTE
+
+
+
+
+
+Segmuller                   Standards Track                     [Page 2]
+
+RFC 3431           Sieve Extension: Relational Tests       December 2002
+
+
+4.1  Match Type Value
+
+   The VALUE match type does a relational comparison between strings.
+
+   The VALUE match type may be used with any comparator which returns
+   sort information.
+
+   Leading and trailing white space MUST be removed from the value of
+   the message for the comparison.  White space is defined as
+
+                             SP / HTAB / CRLF
+
+   A value from the message is considered the left side of the relation.
+   A value from the test expression, the key-list for address, envelope,
+   and header tests, is the right side of the relation.
+
+   If there are multiple values on either side or both sides, the test
+   is considered true, if any pair is true.
+
+4.2  Match Type Count
+
+   The COUNT match type first determines the number of the specified
+   entities in the message and does a relational comparison of the
+   number of entities to the values specified in the test expression.
+
+   The COUNT match type SHOULD only be used with numeric comparators.
+
+   The Address Test counts the number of recipients in the specified
+   fields.  Group names are ignored.
+
+   The Envelope Test counts the number of recipients in the specified
+   envelope parts.  The envelope "to" will always have only one entry,
+   which is the address of the user for whom the sieve script is
+   running.  There is no way a sieve script can determine if the message
+   was actually sent to someone else using this test.  The envelope
+   "from" will be 0 if the MAIL FROM is blank, or 1 if MAIL FROM is not
+   blank.
+
+   The Header Test counts the total number of instances of the specified
+   fields.  This does not count individual addresses in the "to", "cc",
+   and other recipient fields.
+
+   In all cases, if more than one field name is specified, the counts
+   for all specified fields are added together to obtain the number for
+   comparison.  Thus, specifying ["to", "cc"] in an address COUNT test,
+   comparing the total number of "to" and "cc" addresses; if separate
+   counts are desired, they must be done in two comparisons, perhaps
+   joined by "allof" or "anyof".
+
+
+
+Segmuller                   Standards Track                     [Page 3]
+
+RFC 3431           Sieve Extension: Relational Tests       December 2002
+
+
+5 Security Considerations
+
+   Security considerations are discussed in [SIEVE].
+
+   An implementation MUST ensure that the test for envelope "to" only
+   reflects the delivery to the current user.  It MUST not be possible
+   for a user to determine if this message was delivered to someone else
+   using this test.
+
+6 Example
+
+   Using the message:
+
+      received: ...
+      received: ...
+      subject: example
+      to: foo@example.com.invalid, baz@example.com.invalid
+      cc: qux@example.com.invalid
+
+   The test:
+
+        address :count "ge" :comparator "i;ascii-numeric" ["to", "cc"]
+      ["3"]
+
+      would be true and the test
+
+         anyof ( address :count "ge" :comparator "i;ascii-numeric"
+                         ["to"] ["3"],
+                 address :count "ge" :comparator "i;ascii-numeric"
+                         ["cc"] ["3"] )
+
+      would be false.
+
+      To check the number of received fields in the header, the
+      following test may be used:
+
+         header :count "ge" :comparator "i;ascii-numeric"
+                        ["received"] ["3"]
+
+      This would return false.  But
+
+         header :count "ge" :comparator "i;ascii-numeric"
+                          ["received", "subject"] ["3"]
+
+      would return true.
+
+
+
+
+
+
+Segmuller                   Standards Track                     [Page 4]
+
+RFC 3431           Sieve Extension: Relational Tests       December 2002
+
+
+   The test:
+
+         header :count "ge" :comparator "i;ascii-numeric"
+                       ["to", "cc"] ["3"]
+
+   will always return false on an RFC 2822 compliant message [RFC2822],
+   since a message can have at most one "to" field and at most one "cc"
+   field.  This test counts the number of fields, not the number of
+   addresses.
+
+7 Extended Example
+
+   require ["relational", "comparator-i;ascii-numeric"];
+
+   if header :value "lt" :comparator "i;ascii-numeric"
+             ["x-priority"] ["3"]
+   {
+      fileinto "Priority";
+   }
+
+   elseif address :count "gt" :comparator "i;ascii-numeric"
+              ["to"] ["5"]
+   {
+      # everything with more than 5 recipients in the "to" field
+      # is considered SPAM
+      fileinto "SPAM";
+   }
+
+   elseif address :value "gt" :all :comparator "i;ascii-casemap"
+              ["from"] ["M"]
+   {
+      fileinto "From N-Z";
+   } else {
+      fileinto "From A-M";
+   }
+
+   if allof ( address :count "eq" :comparator "i;ascii-numeric"
+                      ["to", "cc"] ["1"] ,
+              address :all :comparator "i;ascii-casemap"
+                      ["to", "cc"] ["me@foo.example.com.invalid"]
+   {
+      fileinto "Only me";
+   }
+
+
+
+
+
+
+
+
+Segmuller                   Standards Track                     [Page 5]
+
+RFC 3431           Sieve Extension: Relational Tests       December 2002
+
+
+8 IANA Considerations
+
+   The following template specifies the IANA registration of the Sieve
+   extension specified in this document:
+
+   To: iana@iana.org
+   Subject: Registration of new Sieve extension
+
+   Capability name: RELATIONAL
+   Capability keyword: relational
+   Capability arguments: N/A
+   Standards Track/IESG-approved experimental RFC number: this RFC
+   Person and email address to contact for further information:
+    Wolfgang Segmuller
+    IBM T.J. Watson Research Center
+    30 Saw Mill River Rd
+    Hawthorne, NY 10532
+
+    Email: whs@watson.ibm.com
+
+   This information should be added to the list of sieve extensions
+   given on http://www.iana.org/assignments/sieve-extensions.
+
+9 References
+
+9.1 Normative References
+
+   [SIEVE]     Showalter, T., "Sieve: A Mail Filtering Language", RFC
+               3028, January 2001.
+
+   [Keywords]  Bradner, S., "Key words for use in RFCs to Indicate
+               Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [ABNF]      Crocker, D., "Augmented BNF for Syntax Specifications:
+               ABNF", RFC 2234, November 1997.
+
+   [RFC2822]   Resnick, P., "Internet Message Format", RFC 2822, April
+               2001.
+
+9.2 Non-Normative References
+
+   [ACAP]      Newman, C. and J. G. Myers, "ACAP -- Application
+               Configuration Access Protocol", RFC 2244, November 1997.
+
+
+
+
+
+
+
+
+Segmuller                   Standards Track                     [Page 6]
+
+RFC 3431           Sieve Extension: Relational Tests       December 2002
+
+
+10 Author's Address
+
+   Wolfgang Segmuller
+   IBM T.J. Watson Research Center
+   30 Saw Mill River Rd
+   Hawthorne, NY  10532
+
+   EMail: whs@watson.ibm.com
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+Segmuller                   Standards Track                     [Page 7]
+
+RFC 3431           Sieve Extension: Relational Tests       December 2002
+
+
+11 Full Copyright Statement
+
+   Copyright (C) The Internet Society (2002).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS 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.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
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+Segmuller                   Standards Track                     [Page 8]
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