draft-ietf-httpbis-safe-method-w-body.xml

<?xml version="1.0"?>
<?rfc toc="yes"?>
<?rfc strict="yes"?>
<?rfc symrefs="yes" ?>
<?rfc sortrefs="yes"?>
<?rfc compact="yes"?>
<?rfc comments="yes"?>
<?rfc inline="yes"?>
<?rfc-ext xml2rfc-backend="202007"?>
<!DOCTYPE rfc [
  <!ENTITY MAY "<bcp14>MAY</bcp14>">
  <!ENTITY MUST "<bcp14>MUST</bcp14>">
  <!ENTITY MUST-NOT "<bcp14>MUST NOT</bcp14>">
  <!ENTITY OPTIONAL "<bcp14>OPTIONAL</bcp14>">
  <!ENTITY RECOMMENDED "<bcp14>RECOMMENDED</bcp14>">
  <!ENTITY REQUIRED "<bcp14>REQUIRED</bcp14>">
  <!ENTITY SHALL "<bcp14>SHALL</bcp14>">
  <!ENTITY SHALL-NOT "<bcp14>SHALL NOT</bcp14>">
  <!ENTITY SHOULD "<bcp14>SHOULD</bcp14>">
  <!ENTITY SHOULD-NOT "<bcp14>SHOULD NOT</bcp14>">
]>
<rfc category="std" ipr="trust200902" docName="draft-ietf-httpbis-safe-method-w-body-latest" submissionType="IETF" updates="5323" version="3" xmlns:xi="http://www.w3.org/2001/XInclude">
  <front>
    <title>
      HTTP SEARCH Method
    </title>

    <author initials="J." surname="Reschke" fullname="Julian Reschke">
      <organization abbrev="greenbytes">greenbytes GmbH</organization>
      <address>
        <postal>
          <street>Hafenweg 16</street>
          <city>Münster</city><code>48155</code>
          <country>Germany</country>
        </postal>
        <email>julian.reschke@greenbytes.de</email>
        <uri>https://greenbytes.de/tech/webdav/</uri>
      </address>
    </author>
    <author initials="A." surname="Malhotra" fullname="Ashok Malhotra">
      <address>
        <email>malhotrasahib@gmail.com</email>
      </address>
    </author>
     <author initials="J.M." surname="Snell" fullname="James M Snell">
      <address>
        <email>jasnell@gmail.com</email>
      </address>
    </author>

    <date/>

    <area>Applications and Real-Time</area>
    <workgroup>HTTP</workgroup>
    <keyword>http</keyword>
    <keyword>search</keyword>
    <keyword>method</keyword>

    <abstract>
      <t>
        This specification updates the definition and semantics of the
        HTTP SEARCH request method originally defined by
        RFC 5323.
      </t>
    </abstract>

    <note title="Editorial Note" removeInRFC="true">
      <t>
        Discussion of this draft takes place on the HTTP working group
        mailing list (ietf-http-wg@w3.org), which is archived at
        <eref target="https://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
      </t>
      <t>
        Working Group information can be found at <eref target="https://httpwg.org/"/>;
        source code and issues list for this draft can be found at
        <eref target="https://github.com/httpwg/http-extensions/labels/safe-method-w-body"/>.
      </t>
      <t>
        The changes in this draft are summarized in <xref target="changes.since.00"/>.
      </t>
    </note>

  </front>

  <middle>

  <section anchor="intro" title="Introduction">

    <t>
      This specification updates the HTTP SEARCH method originally
      defined in <xref target="RFC5323"/>.
    </t>

    <t>
      Many existing HTTP-based applications use the HTTP GET and POST
      methods in various ways to implement the functionality provided
      by SEARCH.
    </t>

    <t>
      Using a GET request with some combination of query parameters included
      within the request URI (as illustrated in the example below) is arguably
      the most common mechanism for implementing search in web applications.
      With this approach, implementations are required to parse the request
      URI into distinct path (everything before the '?') and query elements
      (everything after the '?'). The path identifies the resource processing
      the query (in this case 'http://example.org/feed') while the query
      identifies the specific parameters of the search operation.
    </t>

    <t>
      A typical use of HTTP GET for requesting a search
    </t>
<artwork type="http-message">
GET /feed?q=foo&amp;limit=10&amp;sort=-published HTTP/1.1
Host: example.org
</artwork>

    <t>
      While there are definite advantages to using GET requests in this manner,
      the disadvantages should not be overlooked. Specifically:
    </t>
    <ul>
      <li>
        Without specific knowledge of the resource and server to which the
        GET request is being sent, there is no way for the client to know
        that a search operation is being requested. Identical requests sent
        to two different servers can implement entirely different semantics.
      </li>
      <li>
        Encoding query parameters directly into the request URI effectively
        casts every possible combination of query inputs as distinct
        resources. For instance, because mechanisms such as HTTP caching
        handle request URIs as opaque character sequences, queries such
        as 'http://example.org/?q=foo' and 'http://example.org/?q=Foo'
        will be treated as entirely separate resources even if they
        yield identical results.
      </li>
      <li>
        While most modern browser and server implementations allow for
        long request URIs, there is no standardized minimum or maximum
        length for URIs in general. Many resource constrained devices
        enforce strict limits on the maximum number of characters that can
        be included in a URI. Such limits can prove impractical for
        large or complex query parameters.
      </li>
      <li>
        Query expressions included within a request URI must either be
        restricted to relatively simple key value pairs or encoded
        such that the query can be safely represented in the limited
        character-set allowed by URL standards. Such encoding can add
        significant complexity, introduce bugs, or otherwise reduce the
        overall visibility of the query being requested.
      </li>
    </ul>

    <t>
      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.
    </t>

    <t>
      A typical use of HTTP POST for requesting a search
    </t>
<artwork type="http-message">
POST /feed HTTP/1.1
Host: example.org
Content-Type: application/x-www-form-urlencoded

q=foo&amp;limit=10&amp;sort=-published
</artwork>

    <t>
      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 search
      operation is what is being requested. Web applications use the POST
      method for a wide variety of uses including the creation or modification
      of existing resources. Sending the request above to a different server,
      or even repeatedly sending the request to the same server could have
      dramatically different effects.
    </t>

    <t>
      The SEARCH 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 semantics of the SEARCH
      method are specifically defined.
    </t>

    <t>
      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 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they
      appear in all capitals, as shown here.
    </t>

  </section>

  <section title="SEARCH" anchor="search">

    <t>
      The SEARCH method is used to initiate a server-side search. Unlike
      the HTTP GET method, which requests that a server return a
      representation of the resource identified by the target URI
      (as defined by <xref target="RFCHTTP" section="7.1"/>), the SEARCH
      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 SEARCH
      cannot be assumed to be a representation of the resource identified by
      the effective request URI.
    </t>

    <t>
      The body payload of the request defines the query. Implementations &MAY; use
      a request body of any content type with the SEARCH method; however,
      for backwards compatibility with existing WebDAV implementations,
      SEARCH requests that use the text/xml or application/xml media types
      &MUST; be processed per the requirements established by
      <xref target="RFC5323" />.
      <cref anchor="xml">This can be relaxed to XML with a document element in the "DAV:" namespace, or even to the two element names mentioned in <xref target="RFC5323" section="2.2.2"/>.</cref>
    </t>

    <t>
      SEARCH requests are both safe and idempotent with regards to the
      resource identified by the request URI. That is, SEARCH requests do not
      alter the state of the targeted resource. However, while processing a
      search 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.
    </t>

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

    <t>
      The response to a SEARCH request is not cacheable. It ought to be noted,
      however, that because SEARCH requests are safe and idempotent, responses
      to a SEARCH &MUST-NOT; invalidate previously cached responses to other
      requests directed at the same effective request URI.
      <cref anchor="cache">By default, that is. We need to figure out under which conditions we can make the result cacheable.</cref>
    </t>

    <t>
      The semantics of the SEARCH method change to a "conditional SEARCH" if
      the request message includes an If-Modified-Since, If-Unmodified-
      Since, If-Match, If-None-Match, or If-Range header field
      (<xref target="RFCHTTP" sectionFormat="comma" section="13"/>).  A conditional SEARCH 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.
    </t>

  </section>

  <section title="The &quot;Accept-Search&quot; Header Field" anchor="field.accept-search">
    <t>
      The "Accept-Search" response header field &MAY; be used by a server to
      directly signal support for the SEARCH method while identifying
      the specific query format media types that may be used.
    </t>
<sourcecode type="abnf">
Accept-Search = 1#media-type
</sourcecode>
    <t>
      The Accept-Search header field specifies a comma-separated listing of media
      types (with optional parameters) as defined by
      <xref target="RFCHTTP" section="8.3.1"/>.
    </t>
    <t>
      The order of types listed by the Accept-Search header field is insignificant.
    </t>
  </section>

  <section title="Examples" anchor="examples">

    <t>
      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.
    </t>

    <section title="Simple SEARCH with a Direct Response">

      <t>A simple query with a direct response:</t>
<artwork type="http-message">
SEARCH /contacts HTTP/1.1
Host: example.org
Content-Type: text/query
Accept: text/csv

select surname, givenname, email limit 10
</artwork>

      <t>Response:</t>
<artwork type="http-message">
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
</artwork>

    </section>

    <section title="Simple SEARCH with indirect response (303 See Other)">

      <t>A simple query with an Indirect Response (303 See Other):</t>
<artwork type="http-message">
SEARCH /contacts HTTP/1.1
Host: example.org
Content-Type: text/query
Accept: text/csv

select surname, givenname, email limit 10
</artwork>

      <t>Response:</t>
<artwork type="http-message">
HTTP/1.1 303 See Other
Location: http://example.org/contacts/query123
</artwork>

      <t>Fetch Query Response:</t>
<artwork type="http-message">
GET /contacts/query123 HTTP/1.1
Host: example.org
</artwork>

      <t>Response:</t>
<artwork type="http-message">
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
</artwork>

    </section>

  </section>

  <section title="Security Considerations">
    <t>
      The SEARCH method is subject to the same general security
      considerations as all HTTP methods as described in
      <xref target="RFCHTTP"/>.
    </t>
  </section>

  <section title="IANA Considerations">

    <t>
      IANA is requested to update the registration of the SEARCH method in the
      permanent registry at &lt;http://www.iana.org/assignments/http-methods&gt;
      (see <xref target="RFCHTTP" section="16.1.1"/>).
    </t>

    <table>
      <thead>
        <tr>
          <th>Method Name</th>
          <th>Safe</th>
          <th>Idempotent</th>
          <th>Specification</th>
        </tr>
      </thead>
      <tbody>
        <tr>
          <td>SEARCH</td>
          <td>Yes</td>
          <td>Yes</td>
          <td><xref target="search"/></td>
        </tr>
      </tbody>
    </table>
  </section>

</middle>
<back>
  <references title="Normative References">
    <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>
    <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.5323.xml"/>
    <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>
    <reference anchor="RFCHTTP">
      <front>
        <title>HTTP Semantics</title>
        <author fullname="Roy T. Fielding" initials="R." surname="Fielding" role="editor"/>
        <author fullname="Mark Nottingham" initials="M." surname="Nottingham" role="editor"/>
        <author fullname="Julian Reschke" initials="J." surname="Reschke" role="editor"/>
        <date year="2021" month="March" day="30"/>
      </front>
      <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-semantics-15"/>
    </reference>
  </references>

<section title="Change Log" anchor="change.log" removeInRFC="true">
<t>
  <cref>(see <eref target="https://trac.tools.ietf.org/tools/xml2rfc/trac/ticket/622"/>)</cref>
</t>
<section title="Since draft-ietf-httpbis-safe-method-w-body-00" anchor="changes.since.00">
<ul>
  <li>In <xref target="field.accept-search"/>, adjust the grammar to just define the field value (<eref target="https://github.com/httpwg/http-core/issues/1470"/>)</li>
  <li>Update to latest HTTP core spec, and adjust terminology accordingly (<eref target="https://github.com/httpwg/http-core/issues/1473"/>)</li>
  <li>Reference RFC 8174 and markup bcp14 terms (<eref target="https://github.com/httpwg/http-core/issues/1497"/>)</li>
</ul>
</section>
</section>

</back>
</rfc>