HTTP                                                          J. Reschke
Internet-Draft                                                greenbytes
Intended status: Standards Track                             A. Malhotra
Expires: 13 May 2022
                                                              J.M. Snell
                                                         9 November 2021


                         The HTTP QUERY Method
                draft-ietf-httpbis-safe-method-w-body-02

Abstract

   This specification defines a new HTTP method, QUERY, as a safe,
   idempotent request method that can carry request content.

Editorial Note

   This note is to be removed before publishing as an RFC.

   Discussion of this draft takes place on the HTTP working group
   mailing list (ietf-http-wg@w3.org), which is archived at
   https://lists.w3.org/Archives/Public/ietf-http-wg/.

   Working Group information can be found at https://httpwg.org/; source
   code and issues list for this draft can be found at
   https://github.com/httpwg/http-extensions/labels/safe-method-w-body.

   The changes in this draft are summarized in Appendix A.2.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 13 May 2022.





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Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  QUERY . . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Caching . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  The "Accept-Query" Header Field . . . . . . . . . . . . . . .   5
   4.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Simple QUERY with a Direct Response . . . . . . . . . . .   5
     4.2.  Simple QUERY with indirect response (303 See Other) . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .   7
     A.1.  Since draft-ietf-httpbis-safe-method-w-body-00  . . . . .   8
     A.2.  Since draft-ietf-httpbis-safe-method-w-body-01  . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   This specification defines the HTTP QUERY request method as a means
   of making a safe, idempotent request that contains content.

   Most often, this is desirable when the data conveyed in a request is
   too voluminous to be encoded into the request's URI.  For example,
   while this is an common and interoperable query:

   GET /feed?q=foo&limit=10&sort=-published HTTP/1.1
   Host: example.org









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   if the query parameters extend to several kilobytes or more of data
   it may not be, because many implementations place limits on their
   size.  Often these limits are not known or discoverable ahead of
   time, because a request can pass through many uncoordinated systems.
   Additionally, expressing some data in the target URI is inefficient,
   because it needs to be encoded to be a valid URI.

   Encoding query parameters directly into the request URI also
   effectively casts every possible combination of query inputs as
   distinct resources.  Depending on the application, that may not be
   desirable.

   As an alternative to using GET, many implementations make use of the
   HTTP POST method to perform queries, as illustrated in the example
   below.  In this case, the input parameters to the search operation
   are passed along within the request payload as opposed to using the
   request URI.

   A typical use of HTTP POST for requesting a search

   POST /feed HTTP/1.1
   Host: example.org
   Content-Type: application/x-www-form-urlencoded

   q=foo&limit=10&sort=-published

   This variation, however, suffers from the same basic limitation as
   GET in that it is not readily apparent -- absent specific knowledge
   of the resource and server to which the request is being sent -- that
   a safe, idempotent query is being performed.

   The QUERY method provides a solution that spans the gap between the
   use of GET and POST.  As with POST, the input to the query operation
   is passed along within the payload of the request rather than as part
   of the request URI.  Unlike POST, however, the method is explicitly
   safe and idempotent, allowing functions like caching and automatic
   retries to operate.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.








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2.  QUERY

   The QUERY method is used to initiate a server-side query.  Unlike the
   HTTP GET method, which requests that a server return a representation
   of the resource identified by the target URI (as defined by
   Section 7.1 of [RFCHTTP]), the QUERY method is used to ask the server
   to perform a query operation (described by the request payload) over
   some set of data scoped to the effective request URI.  The payload
   returned in response to a QUERY cannot be assumed to be a
   representation of the resource identified by the effective request
   URI.

   The body payload of the request defines the query.  Implementations
   MAY use a request body of any content type with the QUERY method,
   provided that it has appropriate query semantics.

   QUERY requests are both safe and idempotent with regards to the
   resource identified by the request URI.  That is, QUERY requests do
   not alter the state of the targeted resource.  However, while
   processing a QUERY request, a server can be expected to allocate
   computing and memory resources or even create additional HTTP
   resources through which the response can be retrieved.

   A successful response to a QUERY request is expected to provide some
   indication as to the final disposition of the operation.  For
   instance, a successful query that yields no results can be
   represented by a 204 No Content response.  If the response includes
   content, it is expected to describe the results of the operation.  In
   some cases, the server may choose to respond indirectly to the QUERY
   request by returning a 3xx Redirection with a Location header field
   specifying an alternate Request URI from which the results can be
   retrieved using an HTTP GET request.  Various non-normative examples
   of successful QUERY responses are illustrated in Section 4.

   The semantics of the QUERY method change to a "conditional QUERY" if
   the request message includes an If-Modified-Since, If-Unmodified-
   Since, If-Match, If-None-Match, or If-Range header field ([RFCHTTP],
   Section 13).  A conditional QUERY requests that the query be
   performed only under the circumstances described by the conditional
   header field(s).  It is important to note, however, that such
   conditions are evaluated against the state of the target resource
   itself as opposed to the collected results of the search operation.

2.1.  Caching

   The response to a QUERY method is cacheable; a cache MAY use it to
   satisfy subsequent QUERY requests as per Section 4 of
   [HTTP-CACHING]).



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   The cache key for a query (see Section 2 of [HTTP-CACHING]) MUST
   incorporate the request content.  When doing so, caches SHOULD first
   normalize request content to remove semantically insignificant
   differences, thereby improving cache efficiency, by:

   *  Removing content encoding(s)

   *  Normalizing based upon knowledge of format conventions, as
      indicated by the any media type suffix in the request's Content-
      Type field (e.g., "+json")

   *  Normalizing based upon knowledge of the semantics of the content
      itself, as indicated by the request's Content-Type field.

   Note that any such normalization is performed solely for the purpose
   of generating a cache key; it does not change the request itself.

3.  The "Accept-Query" Header Field

   The "Accept-Query" response header field MAY be used by a server to
   directly signal support for the QUERY method while identifying the
   specific query format media type(s) that may be used.

   Accept-Query = 1#media-type

   The Accept-Query header field specifies a comma-separated listing of
   media types (with optional parameters) as defined by Section 8.3.1 of
   [RFCHTTP].

   The order of types listed by the Accept-Query header field is
   insignificant.

4.  Examples

   The non-normative examples in this section make use of a simple,
   hypothetical plain-text based query syntax based on SQL with results
   returned as comma-separated values.  This is done for illustration
   purposes only.  Implementations are free to use any format they wish
   on both the request and response.

4.1.  Simple QUERY with a Direct Response

   A simple query with a direct response:








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   QUERY /contacts HTTP/1.1
   Host: example.org
   Content-Type: example/query
   Accept: text/csv

   select surname, givenname, email limit 10

   Response:

   HTTP/1.1 200 OK
   Content-Type: text/csv

   surname, givenname, email
   Smith, John, john.smith@example.org
   Jones, Sally, sally.jones@example.com
   Dubois, Camille, camille.dubois@example.net

4.2.  Simple QUERY with indirect response (303 See Other)

   A simple query with an Indirect Response (303 See Other):

   QUERY /contacts HTTP/1.1
   Host: example.org
   Content-Type: example/query
   Accept: text/csv

   select surname, givenname, email limit 10

   Response:

   HTTP/1.1 303 See Other
   Location: http://example.org/contacts/query123

   Fetch Query Response:

   GET /contacts/query123 HTTP/1.1
   Host: example.org

   Response:

   HTTP/1.1 200 OK
   Content-Type: text/csv

   surname, givenname, email
   Smith, John, john.smith@example.org
   Jones, Sally, sally.jones@example.com
   Dubois, Camille, camille.dubois@example.net




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5.  Security Considerations

   The QUERY method is subject to the same general security
   considerations as all HTTP methods as described in [RFCHTTP].

6.  IANA Considerations

   IANA is requested to add QUERY method in the permanent registry at
   <http://www.iana.org/assignments/http-methods> (see Section 16.1.1 of
   [RFCHTTP]).

            +=============+======+============+===============+
            | Method Name | Safe | Idempotent | Specification |
            +=============+======+============+===============+
            | QUERY       | Yes  | Yes        | Section 2     |
            +-------------+------+------------+---------------+

                                  Table 1

7.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFCHTTP]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP Semantics", Work in Progress, Internet-Draft,
              draft-ietf-httpbis-semantics-19, 10 September 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
              semantics-19>.

   [HTTP-CACHING]
              Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP Semantics", Work in Progress, Internet-Draft,
              draft-ietf-httpbis-cache-19, 10 September 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
              cache-19>.

Appendix A.  Change Log

   This section is to be removed before publishing as an RFC.





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A.1.  Since draft-ietf-httpbis-safe-method-w-body-00

   *  Use "example/query" media type instead of undefined "text/query"
      (https://github.com/httpwg/http-extensions/issues/1450)

   *  In Section 3, adjust the grammar to just define the field value
      (https://github.com/httpwg/http-extensions/issues/1470)

   *  Update to latest HTTP core spec, and adjust terminology
      accordingly (https://github.com/httpwg/http-extensions/
      issues/1473)

   *  Reference RFC 8174 and markup bcp14 terms
      (https://github.com/httpwg/http-extensions/issues/1497)

   *  Update HTTP reference (https://github.com/httpwg/http-extensions/
      issues/1524)

   *  Relax restriction of generic XML media type in request body
      (https://github.com/httpwg/http-extensions/issues/1535)

A.2.  Since draft-ietf-httpbis-safe-method-w-body-01

   *  Add minimal description of cacheability
      (https://github.com/httpwg/http-extensions/issues/1552)

   *  Use "QUERY" as method name (https://github.com/httpwg/http-
      extensions/issues/1614)

   *  Update HTTP reference (https://github.com/httpwg/http-extensions/
      issues/1669)

Authors' Addresses

   Julian Reschke
   greenbytes GmbH
   Hafenweg 16
   48155 M√ľnster
   Germany

   Email: julian.reschke@greenbytes.de
   URI:   https://greenbytes.de/tech/webdav/


   Ashok Malhotra

   Email: malhotrasahib@gmail.com




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   James M Snell

   Email: jasnell@gmail.com
















































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