One document matched: draft-ietf-appsawg-uri-get-off-my-lawn-05.xml

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]>

<rfc ipr="trust200902" docName="draft-ietf-appsawg-uri-get-off-my-lawn-05" category="bcp" updates="3986">

<?rfc toc="yes"?>
<?rfc tocindent="yes"?>
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<?rfc strict="yes"?>
<?rfc compact="yes"?>
<?rfc comments="yes"?>
<?rfc inline="yes"?>

  <front>
    <title abbrev="URI Design Ownership">URI Design and Ownership</title>

    <author initials="M." surname="Nottingham" fullname="Mark Nottingham">
      <organization></organization>
      <address>
        
        
        <email>mnot@mnot.net</email>
        <uri>http://www.mnot.net/</uri>
      </address>
    </author>

    <date year="2014"/>

    <area>General</area>
    <workgroup>appsawg</workgroup>
    <keyword>URI structure</keyword>

    <abstract>


<t>RFC3986 Section 1.1.1 defines URI syntax as “a federated and extensible naming system wherein each
scheme’s specification may further restrict the syntax and semantics of identifiers using that
scheme.” In other words, the structure of a URI is defined by its scheme. While it is common for
schemes to further delegate their substructure to the URI’s owner, publishing independent standards
that mandate particular forms of URI substructure is inappropriate, because that essentially usurps
ownership. This document further describes this problematic practice and provides some acceptable
alternatives for use in standards.</t>



    </abstract>


  </front>

  <middle>


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

<t>URIs <xref target="RFC3986"/> very often include structured application data. This might include artifacts
from filesystems (often occurring in the path component), and user information (often in the query
component). In some cases, there can even be application-specific data in the authority component
(e.g., some applications are spread across several hostnames to enable a form of partitioning or
dispatch).</t>

<t>Furthermore, constraints upon the structure of URIs can be imposed by an implementation; for
example, many Web servers use the filename extension of the last path segment to determine the
media type of the response. Likewise, pre-packaged applications often have highly structured URIs
that can only be changed in limited ways (often, just the hostname and port they are deployed upon).</t>

<t>Because the owner of the URI (as defined in <xref target="webarch"/> Section 2.2.2.1) is choosing to use the
server or the application, this can be seen as reasonable delegation of authority. When such
conventions are mandated by a party other than the owner, however, it can have several potentially
detrimental effects:</t>

<t><list style='symbols'>
  <t>Collisions - As more ad hoc conventions for URI structure become standardized, it becomes more
likely that there will be collisions between them (especially considering that servers,
applications and individual deployments will have their own conventions).</t>
  <t>Dilution - When the information added to a URI is ephemeral, this dilutes its utility by reducing
its stability (see <xref target="webarch"/> Section 3.5.1), and can cause several alternate forms of the URI
to exist (see <xref target="webarch"/> Section 2.3.1).</t>
  <t>Rigidity - Fixed URI syntax often interferes with desired deployment patterns. For example, if an
authority wishes to offer several applications on a single hostname, it becomes difficult to
impossible to do if their URIs do not allow the required flexibility.</t>
  <t>Operational Difficulty - Supporting some URI conventions can be difficult in some
implementations. For example, specifying that a particular query parameter be used with “HTTP”
URIs precludes the use of Web servers that serve the response from a filesystem. Likewise, an
application that fixes a base path for its operation (e.g., “/v1”) makes it impossible to deploy
other applications with the same prefix on the same host.</t>
  <t>Client Assumptions - When conventions are standardized, some clients will inevitably assume that
the standards are in use when those conventions are seen. This can lead to interoperability
problems; for example, if a specification documents that the “sig” URI query parameter indicates
that its payload is a cryptographic signature for the URI, it can lead to undesirable behavior.</t>
</list></t>

<t>Publishing a standard that constrains an existing URI structure in ways which aren’t explicitly
allowed by <xref target="RFC3986"/> (usually, by updating the URI scheme definition) is inappropriate, because
the structure of a URI needs to be firmly under the control of its owner, and the IETF (as well as
other organizations) should not usurp it.</t>

<t>This document explains some best current practices for establishing URI structures, conventions and
formats in standards. It also offers strategies for specifications to avoid violating these
guidelines in <xref target="alternatives"/>.</t>

<section anchor="who-this-document-is-for" title="Who This Document Is For">

<t>This document’s requirements target the authors of specifications that constrain the syntax or structure of URIs or parts of them. Two classes of such specifications are called out specifically:</t>

<t><list style='symbols'>
  <t>Protocol Extensions (“extensions”) - specifications that offer new capabilities that could apply
to any identifier, or to a large subset of possible identifiers; e.g., a new signature mechanism
for ‘http’ URIs, or metadata for any URI.</t>
  <t>Applications Using URIs (“applications”) - specifications that use URIs to meet specific needs;
e.g., a HTTP interface to particular information on a host.</t>
</list></t>

<t>Requirements that target the generic class “Specifications” apply to all specifications, including
both those enumerated above and others.</t>

<t>Note that this specification ought not be interpreted as preventing the allocation of control of
URIs by parties that legitimately own them, or have delegated that ownership; for example, a
specification might legitimately define the semantics of a URI on the IANA.ORG Web site as part of
the establishment of a registry.</t>

<t>There may be existing IETF specifications that already deviate from the guidance in this document.
In these cases, it is up to the relevant communities (i.e. those of the URI scheme as well as that
which produced the specification in question) to determine an appropriate outcome; e.g., updating
the scheme definition, or changing the specification.</t>

</section>
<section anchor="notational-conventions" title="Notational Conventions">

<t>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
<xref target="RFC2119"/>.</t>

</section>
</section>
<section anchor="best-current-practices-for-standardizing-structured-uris" title="Best Current Practices for Standardizing Structured URIs">

<t>This section updates <xref target="RFC3986"/> by setting limitations on how other specifications may define
structure and semantics within URIs. Best practices differ depending on the URI component, as
described below.</t>

<section anchor="uri-schemes" title="URI Schemes">

<t>Applications and extensions MAY require use of specific URI scheme(s); for example, it is perfectly
acceptable to require that an application support ‘http’ and ‘https’ URIs. However, applications
SHOULD NOT preclude the use of other URI schemes in the future, unless they are clearly only usable
with the nominated schemes.</t>

<t>A specification that defines substructure within a specific URI scheme MUST do so in the defining
document for that URI scheme. A specification that defines substructure for URI schemes overall
MUST do so by modifying <xref target="BCP115"/> (an exceptional circumstance).</t>

</section>
<section anchor="uri-authorities" title="URI Authorities">

<t>Scheme definitions define the presence, format and semantics of an authority component in URIs; all
other specifications MUST NOT constrain, or define the structure or the semantics for URI
authorities, unless they update the scheme registration itself.</t>

<t>For example, an extension or application ought not say that the “foo” prefix in
“foo_app.example.com” is meaningful or triggers special handling in URIs.</t>

<t>However, applications MAY nominate or constrain the port they use, when applicable. For example, 
BarApp could run over port nnnn (provided that it is properly registred).</t>

</section>
<section anchor="uri-paths" title="URI Paths">

<t>Scheme definitions define the presence, format, and semantics of a path component in URIs; all
other specifications MUST NOT constrain, or define the structure or the semantics for any path
component.</t>

<t>The only exception to this requirement is registered “well-known” URIs, as specified by <xref target="RFC5785"/>.
See that document for a description of the applicability of that mechanism.</t>

<t>For example, an application ought not specify a fixed URI path “/myapp”, since this usurps the
host’s control of that space.</t>

<t>Specifying a fixed path relative to another (e.g., {whatever}/myapp) is also bad practice (even if
“whatever” is discovered as suggested in <xref target="alternatives"/>); while doing so might prevent
collisions, it does not avoid the potential for operational difficulties (for example, an
implementation that prefers to use query processing instead, because of implementation constraints).</t>

</section>
<section anchor="uri-queries" title="URI Queries">

<t>The presence, format and semantics of the query component of URIs is dependent upon many factors,
and MAY be constrained by a scheme definition. Often, they are determined by the implementation of
a resource itself.</t>

<t>Applications MUST NOT directly specify the syntax of queries, as this can cause operational
difficulties for deployments that do not support a particular form of a query. For example, a site may wish to support an application using “static” files that do not support query parameters.</t>

<t>Extensions MUST NOT constrain the format or semantics of queries.</t>

<t>For example, an extension that indicates that all query parameters with the name “sig” indicate a
cryptographic signature would collide with potentially pre-existing query parameters on sites, and
lead clients to assume that any matching query parameter is a signature.</t>

<t>HTML <xref target="W3C.REC-html401-19991224"/> constrains the syntax of query strings used in form submission.
New form languages SHOULD NOT emulate it, but instead allow creation of a broader variety of URIs
(e.g., by allowing the form to create new path components, and so forth).</t>

<t>Note that “well-known” URIs (see <xref target="RFC5785"/>) MAY constrain their own query syntax, since these
name spaces are effectively delegated to the registering party.</t>

</section>
<section anchor="uri-fragment-identifiers" title="URI Fragment Identifiers">

<t>Media type definitions (as per <xref target="RFC6838"/>) SHOULD specify the fragment identifier syntax(es) to be
used with them; other specifications MUST NOT define structure within the fragment identifier,
unless they are explicitly defining one for reuse by media type definitions.</t>

<t>For example, an application that defines common fragment identifiers across media types not
controlled by it would engender interoperability problems with handlers for those media types
(because the new, non-standard syntax is not expected).</t>

</section>
</section>
<section anchor="alternatives" title="Alternatives to Specifying Structure in URIs">

<t>Given the issues described in <xref target="intro"/>, the most successful strategy for applications and
extensions that wish to use URIs is to use them in the fashion they were designed: as links that
are exchanged as part of the protocol, rather than statically specified syntax. Several existing
specifications can aid in this.</t>

<t><xref target="RFC5988"/> specifies relation types for Web links. By providing a framework for linking on the
Web, where every link has a relation type, context and target, it allows applications to define a
link’s semantics and connectivity.</t>

<t><xref target="RFC6570"/> provides a standard syntax for URI Templates that can be used to dynamically insert
application-specific variables into a URI to enable such applications while avoiding impinging upon
URI owners’ control of them.</t>

<t><xref target="RFC5785"/> allows specific paths to be ‘reserved’ for standard use on URI schemes that opt into
that mechanism (‘http’ and ‘https’ by default). Note, however, that this is not a general “escape
valve” for applications that need structured URIs; see that specification for more information.</t>

<t>Specifying more elaborate structures in an attempt to avoid collisions is not an acceptable
solution, and does not address the issues in <xref target="intro"/>. For example, prefixing query parameters
with “myapp_” does not help, because the prefix itself is subject to the risk of collision (since
it is not “reserved”).</t>

</section>
<section anchor="security-considerations" title="Security Considerations">

<t>This document does not introduce new protocol artifacts with security considerations. It prohibits
some practices that might lead to vulnerabilities; for example, if a security-sensitive mechanism
is introduced by assuming that a URI path component or query string has a particular meaning, false
positives might be encountered (due to sites that already use the chosen string). See also
<xref target="RFC6943"/>.</t>

</section>
<section anchor="iana-considerations" title="IANA Considerations">

<t>There are no direct IANA actions specified in this document.</t>

</section>


  </middle>

  <back>

    <references title='Normative References'>





<reference anchor='RFC2119'>

<front>
<title abbrev='RFC Key Words'>Key words for use in RFCs to Indicate Requirement Levels</title>
<author initials='S.' surname='Bradner' fullname='Scott Bradner'>
<organization>Harvard University</organization>
<address>
<postal>
<street>1350 Mass. Ave.</street>
<street>Cambridge</street>
<street>MA 02138</street></postal>
<phone>- +1 617 495 3864</phone>
<email>sob@harvard.edu</email></address></author>
<date year='1997' month='March' />
<area>General</area>
<keyword>keyword</keyword>
<abstract>
<t>
   In many standards track documents several words are used to signify
   the requirements in the specification.  These words are often
   capitalized.  This document defines these words as they should be
   interpreted in IETF documents.  Authors who follow these guidelines
   should incorporate this phrase near the beginning of their document:

<list>
<t>
      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
      RFC 2119.
</t></list></t>
<t>
   Note that the force of these words is modified by the requirement
   level of the document in which they are used.
</t></abstract></front>

<seriesInfo name='BCP' value='14' />
<seriesInfo name='RFC' value='2119' />
<format type='TXT' octets='4723' target='http://www.rfc-editor.org/rfc/rfc2119.txt' />
<format type='HTML' octets='17970' target='http://xml.resource.org/public/rfc/html/rfc2119.html' />
<format type='XML' octets='5777' target='http://xml.resource.org/public/rfc/xml/rfc2119.xml' />
</reference>



<reference anchor='RFC3986'>

<front>
<title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
<author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
<organization abbrev='W3C/MIT'>World Wide Web Consortium</organization>
<address>
<postal>
<street>Massachusetts Institute of Technology</street>
<street>77 Massachusetts Avenue</street>
<city>Cambridge</city>
<region>MA</region>
<code>02139</code>
<country>USA</country></postal>
<phone>+1-617-253-5702</phone>
<facsimile>+1-617-258-5999</facsimile>
<email>timbl@w3.org</email>
<uri>http://www.w3.org/People/Berners-Lee/</uri></address></author>
<author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
<organization abbrev='Day Software'>Day Software</organization>
<address>
<postal>
<street>5251 California Ave., Suite 110</street>
<city>Irvine</city>
<region>CA</region>
<code>92617</code>
<country>USA</country></postal>
<phone>+1-949-679-2960</phone>
<facsimile>+1-949-679-2972</facsimile>
<email>fielding@gbiv.com</email>
<uri>http://roy.gbiv.com/</uri></address></author>
<author initials='L.' surname='Masinter' fullname='Larry Masinter'>
<organization abbrev='Adobe Systems'>Adobe Systems Incorporated</organization>
<address>
<postal>
<street>345 Park Ave</street>
<city>San Jose</city>
<region>CA</region>
<code>95110</code>
<country>USA</country></postal>
<phone>+1-408-536-3024</phone>
<email>LMM@acm.org</email>
<uri>http://larry.masinter.net/</uri></address></author>
<date year='2005' month='January' />
<area>Applications</area>
<keyword>uniform resource identifier</keyword>
<keyword>URI</keyword>
<keyword>URL</keyword>
<keyword>URN</keyword>
<keyword>WWW</keyword>
<keyword>resource</keyword>
<abstract>
<t>
A Uniform Resource Identifier (URI) is a compact sequence of characters
that identifies an abstract or physical resource.  This specification
defines the generic URI syntax and a process for resolving URI references
that might be in relative form, along with guidelines and security
considerations for the use of URIs on the Internet.
The URI syntax defines a grammar that is a superset of all valid URIs,
allowing an implementation to parse the common components of a URI
reference without knowing the scheme-specific requirements of every
possible identifier.  This specification does not define a generative
grammar for URIs; that task is performed by the individual
specifications of each URI scheme.
</t></abstract></front>

<seriesInfo name='STD' value='66' />
<seriesInfo name='RFC' value='3986' />
<format type='TXT' octets='141811' target='http://www.rfc-editor.org/rfc/rfc3986.txt' />
<format type='HTML' octets='214067' target='http://xml.resource.org/public/rfc/html/rfc3986.html' />
<format type='XML' octets='163534' target='http://xml.resource.org/public/rfc/xml/rfc3986.xml' />
</reference>



<reference anchor='RFC6838'>

<front>
<title>Media Type Specifications and Registration Procedures</title>
<author initials='N.' surname='Freed' fullname='N. Freed'>
<organization /></author>
<author initials='J.' surname='Klensin' fullname='J. Klensin'>
<organization /></author>
<author initials='T.' surname='Hansen' fullname='T. Hansen'>
<organization /></author>
<date year='2013' month='January' />
<abstract>
<t>This document defines procedures for the specification and registration of media types for use in HTTP, MIME, and other Internet protocols.  This memo documents an Internet Best Current Practice.</t></abstract></front>

<seriesInfo name='BCP' value='13' />
<seriesInfo name='RFC' value='6838' />
<format type='TXT' octets='72942' target='http://www.rfc-editor.org/rfc/rfc6838.txt' />
</reference>


<reference anchor="webarch" target="http://www.w3.org/TR/2004/REC-webarch-20041215">
  <front>
    <title>Architecture of the World Wide Web, Volume One</title>
    <author initials="I." surname="Jacobs" fullname="Ian Jacobs">
      <organization></organization>
    </author>
    <author initials="N." surname="Walsh" fullname="Norman Walsh">
      <organization></organization>
    </author>
    <date year="2004" month="December" day="15"/>
  </front>
</reference>


    </references>

    <references title='Informative References'>

<reference anchor="BCP115" target="https://tools.ietf.org/html/bcp115">
  <front>
    <title>Guidelines and Registration Procedures for New URI Schemes</title>
    <author initials="T." surname="Hansen" fullname="Tony Hansen">
      <organization>AT&T Laboratories</organization>
    </author>
    <author initials="T." surname="Hardie" fullname="Ted Hardie">
      <organization>Qualcomm, Inc.</organization>
    </author>
    <author initials="L." surname="Masinter" fullname="Larry Masinter">
      <organization>Adobe Systems</organization>
    </author>
    <date year="2006" month="February"/>
  </front>
  <seriesInfo name="RFC" value="4395"/>
  <seriesInfo name="BCP" value="115"/>
</reference>




<reference anchor='RFC5785'>

<front>
<title>Defining Well-Known Uniform Resource Identifiers (URIs)</title>
<author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
<organization /></author>
<author initials='E.' surname='Hammer-Lahav' fullname='E. Hammer-Lahav'>
<organization /></author>
<date year='2010' month='April' />
<abstract>
<t>This memo defines a path prefix for "well-known locations", "/.well-known/", in selected Uniform Resource Identifier (URI) schemes. [STANDARDS-TRACK]</t></abstract></front>

<seriesInfo name='RFC' value='5785' />
<format type='TXT' octets='13779' target='http://www.rfc-editor.org/rfc/rfc5785.txt' />
</reference>



<reference anchor='RFC5988'>

<front>
<title>Web Linking</title>
<author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
<organization /></author>
<date year='2010' month='October' />
<abstract>
<t>This document specifies relation types for Web links, and defines a registry for them.  It also defines the use of such links in HTTP headers with the Link header field. [STANDARDS-TRACK]</t></abstract></front>

<seriesInfo name='RFC' value='5988' />
<format type='TXT' octets='46834' target='http://www.rfc-editor.org/rfc/rfc5988.txt' />
</reference>



<reference anchor='RFC6570'>

<front>
<title>URI Template</title>
<author initials='J.' surname='Gregorio' fullname='J. Gregorio'>
<organization /></author>
<author initials='R.' surname='Fielding' fullname='R. Fielding'>
<organization /></author>
<author initials='M.' surname='Hadley' fullname='M. Hadley'>
<organization /></author>
<author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
<organization /></author>
<author initials='D.' surname='Orchard' fullname='D. Orchard'>
<organization /></author>
<date year='2012' month='March' />
<abstract>
<t>A URI Template is a compact sequence of characters for describing a range of Uniform Resource Identifiers through variable expansion.  This specification defines the URI Template syntax and the process for expanding a URI Template into a URI reference, along with guidelines for the use of URI Templates on the Internet. [STANDARDS-TRACK]</t></abstract></front>

<seriesInfo name='RFC' value='6570' />
<format type='TXT' octets='79813' target='http://www.rfc-editor.org/rfc/rfc6570.txt' />
</reference>



<reference anchor='RFC6943'>

<front>
<title>Issues in Identifier Comparison for Security Purposes</title>
<author initials='D.' surname='Thaler' fullname='D. Thaler'>
<organization /></author>
<date year='2013' month='May' />
<abstract>
<t>Identifiers such as hostnames, URIs, IP addresses, and email addresses are often used in security contexts to identify security principals and resources.  In such contexts, an identifier presented via some protocol is often compared using some policy to make security decisions such as whether the security principal may access the resource, what level of authentication or encryption is required, etc.  If the parties involved in a security decision use different algorithms to compare identifiers, then failure scenarios ranging from denial of service to elevation of privilege can result.  This document provides a discussion of these issues that designers should consider when defining identifiers and protocols, and when constructing architectures that use multiple protocols.</t></abstract></front>

<seriesInfo name='RFC' value='6943' />
<format type='TXT' octets='62676' target='http://www.rfc-editor.org/rfc/rfc6943.txt' />
</reference>



<reference anchor='W3C.REC-html401-19991224'
           target='http://www.w3.org/TR/1999/REC-html401-19991224'>
<front>
<title>HTML 4.01 Specification</title>

<author initials='D.' surname='Raggett' fullname='Dave Raggett'>
    <organization />
</author>

<author initials='A.' surname='Hors' fullname='Arnaud Le Hors'>
    <organization />
</author>

<author initials='I.' surname='Jacobs' fullname='Ian Jacobs'>
    <organization />
</author>

<date month='December' day='24' year='1999' />
</front>

<seriesInfo name='World Wide Web Consortium Recommendation' value='REC-html401-19991224' />
<format type='HTML' target='http://www.w3.org/TR/1999/REC-html401-19991224' />
</reference>




    </references>


<section anchor="acknowledgments" title="Acknowledgments">

<t>Thanks to David Booth, Dave Crocker, Tim Bray, Anne van Kesteren, Martin Thomson, Erik Wilde,
Dave Thaler and Barry Leiba for their suggestions and feedback.</t>

</section>


  </back>
</rfc>