IMAP Extension for Referencing the Last SEARCH Result
RFC 5182

Received changes through RFC Editor sync (changed abstract to 'Many IMAP clients use the result of a SEARCH command as the input to perform another operation, for example, fetching the found messages, deleting them, or copying them to another mailbox.

This can be achieved using standard IMAP operations described in RFC 3501; however, this would be suboptimal. The server will send the list of found messages to the client; after that, the client will have to parse the list, reformat it, and send it back to the server. The client can't pipeline the SEARCH command with the subsequent command, and, as a result, the server might not be able to perform some optimizations.

This document proposes an IMAP extension that allows a client to tell a server to use the result of a SEARCH (or Unique Identifier (UID) SEARCH) command as an input to any subsequent command. [STANDARDS-TRACK]')

[Ballot comment]
Christian Vogt's review:

This document specifies an IMAP extension that calls for servers to store search results in a way referable by clients in subsequent requests.

The document is ready for publication once the issues described below has been addressed.  The document clearly motivates the proposed IMAP extension, specifies it in an understandable manner, and accompanies this with a rich set of examples.

Two issues need to be addressed, however:

- Overall:  For how long should a server store a given search result?  The current document does not talk about state expiry.  State expiry is important to address, however, given the large amount of memory that is potentially needed to hold a search result.

I would specifically suggest to let the state expiry interval be determined by the server.  This enables the server to discard search results earlier when memory availability is low.  Reduction in state expiry intervals may also be used as a defense against DoS (and hence should mentioned in the security considerations).

- Section 2.1, 3rd paragraph:  What is the format in which lists are stored?  This paragraph may refer to a data type from the IMAP specification to be more specific.

[Ballot discuss]
The Gen-ART Review by Spencer Dawkins of draft -06.  Since there was
  no reply to the Gen-ART Review, it is difficult to tell if the changes
  made to generate draft -07 were to address the concerns raised in the
  Gen-ART Review or other comments.  I've asked Spencer to take a look,
  but I have not heard back from him yet.  The Gen-ART Review can be
  found at:

    http://www.alvestrand.no/ietf/gen/reviews/
    draft-melnikov-imap-search-res-06-dawkins.txt

[Ballot comment]
Does the implementation note in section 2.1 mean that implementors are required to
convert a message sequence to a UID sequence, and vice versa?  If this is mandatory
to implement, perhaps a statement in the normative text would be worth adding...

IANA Last Call comments:


Upon approval of this document, the IANA will make the following
assignments in the "IMAP Capabilities Registry" registry located at
http://www.iana.org/assignments/imap4-capabilities

Capability Name + Reference
-------- + ---------
SEARCH-RES + [RFC-melnikov-imap-search-res-06]

We understand the above to be the only IANA Action for this
document.

Write-up from author:

  (1.b)  Has the document had adequate review both from key WG members
          and from key non-WG members?  Does the Document Shepherd have
          any concerns about the depth or breadth of the reviews that
          have been performed?

This document was reviewed by several active and experienced IMAPEXT WG
members.
So there are no concerns about the depth of the reviews.

  (1.c)  Does the Document Shepherd have concerns that the document
          needs more review from a particular or broader perspective,
          e.g., security, operational complexity, someone familiar with
          AAA, internationalization or XML?

No concerns.

  (1.d)  Does the Document Shepherd have any specific concerns or
          issues with this document that the Responsible Area Director
          and/or the IESG should be aware of?  For example, perhaps he
          or she is uncomfortable with certain parts of the  document, or
          has concerns whether there really is a need for it.  In any
          event, if the WG has discussed those issues and has indicated
          that it still wishes to advance the document, detail those
          concerns here.  Has an IPR disclosure related to this  document
          been filed?  If so, please include a reference to the
          disclosure and summarize the WG discussion and conclusion on
          this issue.

No specific concerns. No IPR disclosure was filed for this document.

  (1.e)  How solid is the WG consensus behind this document?  Does it
          represent the strong concurrence of a few individuals, with
          others being silent, or does the WG as a whole understand and
          agree with it?

This document is an individual submission.

  (1.f)  Has anyone threatened an appeal or otherwise indicated  extreme
          discontent?  If so, please summarise the areas of conflict in
          separate email messages to the Responsible Area Director.  (It
          should be in a separate email because this questionnaire is
          entered into the ID Tracker.)
No.

  (1.g)  Has the Document Shepherd personally verified that the
          document satisfies all ID nits?  (See
          http://www.ietf.org/ID-Checklist.html and
          http://tools.ietf.org/tools/idnits/).  Boilerplate checks are
          not enough; this check needs to be thorough.  Has the  document
          met all formal review criteria it needs to, such as the MIB
          Doctor, media type and URI type reviews?

Yes. IDnits 2.02.2 returns one experimental warning, which is due to use
of IMAP response
code, and thus is not an error. There is also a warning about missing
page separators, which
can be fixed by an RFC editor.

  (1.h)  Has the document split its references into normative and
          informative?  Are there normative references to documents  that
          are not ready for advancement or are otherwise in an unclear
          state?  If such normative references exist, what is the
          strategy for their completion?  Are there normative  references
          that are downward references, as described in [RFC3967]?  If
          so, list these downward references to support the Area
          Director in the Last Call procedure for them [RFC3967].

Yes, references are properly split. There are no downward normative
references.
All normative references are to documents which are already RFCs.
One informative reference points to an IMAPEXT WG draft, which is in
IESG evaluation now.

  (1.i)  Has the Document Shepherd verified that the document IANA
          consideration section exists and is consistent with the body
          of the document?  If the document specifies protocol
          extensions, are reservations requested in appropriate IANA
          registries?  Are the IANA registries clearly identified?  If
          the document creates a new registry, does it define the
          proposed initial contents of the registry and an allocation
          procedure for future registrations?  Does it suggest a
          reasonable name for the new registry?  See [RFC2434].  If the
          document describes an Expert Review process has Shepherd
          conferred with the Responsible Area Director so that the IESG
          can appoint the needed Expert during the IESG Evaluation?

IANA considerations section exists and is clearly defined.

  (1.j)  Has the Document Shepherd verified that sections of the
          document that are written in a formal language, such as XML
          code, BNF rules, MIB definitions, etc., validate correctly in
          an automated checker?

ABNF from the document passes Bill Fenner's ABNF validation tool.

  (1.k)  The IESG approval announcement includes a Document
          Announcement Write-Up.  Please provide such a Document
          Announcement Write-Up?  Recent examples can be found in the
          "Action" announcements for approved documents.  The approval
          announcement contains the following sections:

          Technical Summary
            Relevant content can frequently be found in the abstract
            and/or introduction of the document.  If not, this may be
            an indication that there are deficiencies in the abstract
            or introduction.

  Many IMAP clients use the result of a SEARCH command as the input to
  perform another operation, for example fetching the found messages,
  deleting them, copying them to another mailbox or performing a
  subsearch on the found messages.

  This can be achieved using standard IMAP operations described in RFC
  3501, however this would be suboptimal: the server will send the list
  of found messages to the client, after that the client will have to
  parse the list, reformat it and send it back to the server.  As the
  result, the client can't pipeline the SEARCH command with the
  subsequent command.

  This document proposes an IMAP extension that allows a client to tell
  a server to use the result of a SEARCH (or UID SEARCH)
  command as an input to a subsequent command.

          Working Group Summary
            Was there anything in WG process that is worth noting?  For
            example, was there controversy about particular points or
            were there decisions where the consensus was particularly
            rough?

This document is an individual submission.

          Document Quality
            Are there existing implementations of the protocol?  Have a
            significant number of vendors indicated their plan to
            implement the specification?  Are there any reviewers that
            merit special mention as having done a thorough review,
            e.g., one that resulted in important changes or a
            conclusion that the document had no substantive  issues?  If
            there was a MIB Doctor, Media Type or other expert review,
            what was its course (briefly)?  In the case of a Media  Type
            review, on what date was the request posted?

There are already 2 server implementations of this document. At least
one more client and server vendor is interested in implementing the specification.

          Personnel
            Who is the Document Shepherd for this document?  Who is  the
            Responsible Area Director?

Alexey Melnikov  is the document shepherd for
this document. Chris Newman is the responsible Area Director.