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Versions: 00 01 04 05 06 07 08 09 10 RFC 7351

Network Working Group                                           E. Wilde
Internet-Draft                                                       EMC
Intended status: Standards Track                        January 16, 2013
Expires: July 20, 2013


                 A Media Type for XML Patch Operations
                        draft-wilde-xml-patch-01

Abstract

   The XML Patch media type "application/xml-patch+xml" defines an XML
   document structure for expressing a sequence of patch operations that
   are applied to an XML document.  The XML Patch document format's
   foundations are defined in RFC 5261, this specification defines a
   document format and a media type registration, so that XML Patch
   documents can be labeled with a media type, for example in HTTP
   conversations.

Note to Readers

   This draft should be discussed on the apps-discuss mailing list [8].

   Online access to all versions and files is available at github [9].

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   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 July 20, 2013.

Copyright Notice

   Copyright (c) 2013 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



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   Provisions Relating to IETF Documents
   (http://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
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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  3
   3.  Patch Document Format  . . . . . . . . . . . . . . . . . . . .  4
   4.  Patch Examples . . . . . . . . . . . . . . . . . . . . . . . .  5
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  6
   6.  Change Log . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     6.1.  From -00 to -01  . . . . . . . . . . . . . . . . . . . . .  6
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     7.1.  Normative References . . . . . . . . . . . . . . . . . . .  6
     7.2.  Informative References . . . . . . . . . . . . . . . . . .  7
   Appendix A.  XSD from RFC 5261 . . . . . . . . . . . . . . . . . .  7
   Appendix B.  ABNF for RFC 5261 . . . . . . . . . . . . . . . . . .  9
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10


























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1.  Introduction

   The Extensible Markup Language (XML) [1] is a common format for the
   exchange and storage of structured data.  HTTP PATCH [6] extends HTTP
   [7] with a method to perform partial modifications to resources.
   HTTP PATCH requires that patch documents are being sent along with
   the request, and it is therefore useful if there are standardized
   patch document formats (identified by media types) for popular media
   types.

   The XML Patch media type "application/xml-patch+xml" is an XML
   document structure for expressing a sequence of operations to apply
   to a target XML document, suitable for use with the HTTP PATCH
   method.  Servers can freely choose which patch formats they want to
   accept, and "application/xml-patch+xml" could be a simple default
   format that can be used unless a server decides to use a different
   (maybe more sophisticated) patch format for XML.

   The format for patch documents is based on the XML Patch Framework
   defined in RFC 5261 [2].  While RFC 5261 does define a concrete
   syntax as well as the media type "application/patch-ops-error+xml"
   for error documents, it only defines XSD types for patch operations,
   and thus the concrete document format and the media type for patch
   operations are defined in an XSD defined in this specification.


2.  IANA Considerations

   The Internet media type [3] for an XML Patch Document is application/
   xml-patch+xml.

      Type name: application

      Subtype name: xml-patch+xml

      Required parameters: none

      Optional parameters: Same as charset parameter for the media type
      "application/xml" as specified in RFC 3023 [1].

      Encoding considerations: Same as encoding considerations of media
      type "application/xml" as specified in RFC 3023 [1].

      Security considerations: This media type has all of the security
      considerations described in RFC 3023 [1] and RFC 5261 [2], plus
      those listed in Section 5.





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      Interoperability considerations: N/A

      Published specification: RFC XXXX

      Applications that use this media type: Applications that
      manipulate XML documents.

      Additional information:

         Magic number(s): N/A

         File extension(s): XML documents should use ".xml" as the file
         extension.

         Macintosh file type code(s): TEXT

      Person & email address to contact for further information: Erik
      Wilde <erik.wilde@emc.com>

      Intended usage: COMMON

      Restrictions on usage: none

      Author: Erik Wilde <erik.wilde@emc.com>

      Change controller: IETF


3.  Patch Document Format

   The XML patch document format is based on a simple schema that uses a
   "patch" element as the document element, and allows a arbitrary
   sequence of "add", "remove", and "replace" elements as the children
   of the document element.  These children follow the semantics defined
   in RFC 5261, which means that each element is treated as an
   individual patch operation, and the result of each patch operation is
   a patched XML document that is the target XML document for the next
   patch operation.

   The following example patch document uses the example from RFC 5261,
   and simply uses a "patch" element and a new XML namespace.  It shows
   the general structure of an XML patch document, as well as an example
   for each operation.








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<p:patch xmlns="urn:ietf:params:xml:ns:xxx" xmlns:y="urn:ietf:params:xml:ns:yyy"
    xmlns:p="urn:ietf:rfc:XXXX" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="urn:ietf:rfc:XXXX patch-document-00.xsd">
    <p:add sel="doc/elem[@a='foo']">
        <!-- This is a new child -->
        <child id="ert4773">
            <y:node/>
        </child>
    </p:add>
    <p:replace sel="doc/note/text()">Patched doc</p:replace>
    <p:remove sel="*/elem[@a='bar']/y:child" ws="both"/>
    <p:add sel="*/elem[@a='bar']" type="@b">new attr</p:add>
</p:patch>

   As this example demonstrates, both the document element "patch" and
   the patch operation elements are in the same XML namespace.  This is
   the result of RFC 5261 only defining types for the patch operation
   elements, which then can be reused in schemas to define concrete
   patch elements.

   RFC 5261 defines an XML Schema (XSD) for the patch operation types,
   which is included for reference in Appendix A.  The normative version
   of this schema is the one given in RFC 5261.  The following schema
   for the XML Patch media type is based on the types defined in RFC
   5261, which are imported as "rfc5261.xsd" in the following schema.
   The schema defines a "patch" document element, and then allows an
   unlimited (and possible empty) sequence of the "add", "remove", and
   "replace" operation elements, which are directly based on the
   respective types from the schema defined in RFC 5261.
<xs:schema targetNamespace="urn:ietf:rfc:XXXX"
    xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
    <xs:import schemaLocation="rfc5261.xsd"/>
    <xs:element name="patch">
        <xs:complexType>
            <xs:choice minOccurs="0" maxOccurs="unbounded">
                <xs:element name="add" type="add"/>
                <xs:element name="remove" type="remove"/>
                <xs:element name="replace" type="replace"/>
            </xs:choice>
        </xs:complexType>
    </xs:element>
</xs:schema>


4.  Patch Examples

   Since the semantics of the XML patch operations are defined by RFC
   5261, please refer to the numerous examples in that specification for



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   concrete XML patch document examples.  Most importantly, the examples
   in RFC 5261 can be taken literally as examples for the XML Patch
   media type, as long as it is assumed that the XML namespace for the
   operation elements in these examples is the URI "urn:ietf:rfc:XXXX".


5.  Security Considerations

   ...


6.  Change Log

   Note to RFC Editor: Please remove this section before publication.

6.1.  From -00 to -01

   o  Removed Mark Nottingham from author list.

   o  Changed media type name to application/xml-patch+xml (added suffix
      per draft-ietf-appsawg-media-type-suffix-regs)

   o  Added ABNF grammar derived from XSD (Appendix B)


7.  References

7.1.  Normative References

   [1]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types",
        RFC 3023, January 2001.

   [2]  Urpalainen, J., "An Extensible Markup Language (XML) Patch
        Operations Framework Utilizing XML Path Language (XPath)
        Selectors", RFC 5261, September 2008.

   [3]  Freed, N. and J. Klensin, "Media Type Specifications and
        Registration Procedures", BCP 13, RFC 4288, December 2005.

   [4]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
        Extensions (MIME) Part One: Format of Internet Message Bodies",
        RFC 2045, November 1996.

   [5]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
        Extensions (MIME) Part Two: Media Types", RFC 2046,
        November 1996.





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7.2.  Informative References

   [6]  Dusseault, L. and J. Snell, "PATCH Method for HTTP", RFC 5789,
        March 2010.

   [7]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,
        Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol --
        HTTP/1.1", RFC 2616, June 1999.

URIs

   [8]  <https://www.ietf.org/mailman/listinfo/apps-discuss>

   [9]  <https://github.com/dret/I-D/tree/master/xml-patch>


Appendix A.  XSD from RFC 5261

   For reference, this section contains a copy of the XSD defining the
   add, replace, and remove types in RFC 5261 [2].  This section is
   informational only, and the definitive version of the schema is the
   one listed in RFC 5261.
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE schema [
    <!ENTITY ncname "\i\c*">
    <!ENTITY qname  "(&ncname;:)?&ncname;">
    <!ENTITY aname  "@&qname;">
    <!ENTITY pos    "\[\d+\]">
    <!ENTITY attr   "\[&aname;='(.)*'\]|\[&aname;=&quot;(.)*&quot;\]">
    <!ENTITY valueq "\[(&qname;|\.)=&quot;(.)*&quot;\]">
    <!ENTITY value  "\[(&qname;|\.)='(.)*'\]|&valueq;">
    <!ENTITY cond   "&attr;|&value;|&pos;">
    <!ENTITY step   "(&qname;|\*)(&cond;)*">
    <!ENTITY piq    "processing-instruction\((&quot;&ncname;&quot;)\)">
    <!ENTITY pi     "processing-instruction\(('&ncname;')?\)|&piq;">
    <!ENTITY id     "id\(('&ncname;')?\)|id\((&quot;&ncname;&quot;)?\)">
    <!ENTITY com    "comment\(\)">
    <!ENTITY text   "text\(\)">
    <!ENTITY nspa   "namespace::&ncname;">
    <!ENTITY cnodes "(&text;(&pos;)?)|(&com;(&pos;)?)|((&pi;)(&pos;)?)">
    <!ENTITY child  "&cnodes;|&step;">
    <!ENTITY last   "(&child;|&aname;|&nspa;)">
    ]>
<xsd:schema
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    elementFormDefault="qualified">

    <xsd:simpleType name="xpath">



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        <xsd:restriction base="xsd:string">
            <xsd:pattern
                value="(/)?((&id;)((/&step;)*(/&last;))?|(&step;/)*(&last;))"/>
        </xsd:restriction>
    </xsd:simpleType>

    <xsd:simpleType name="xpath-add">
        <xsd:restriction base="xsd:string">
            <xsd:pattern
                value="(/)?((&id;)((/&step;)*(/&child;))?|(&step;/)*(&child;))"/>
        </xsd:restriction>
    </xsd:simpleType>

    <xsd:simpleType name="pos">
        <xsd:restriction base="xsd:string">
            <xsd:enumeration value="before"/>
            <xsd:enumeration value="after"/>
            <xsd:enumeration value="prepend"/>
        </xsd:restriction>
    </xsd:simpleType>

    <xsd:simpleType name="type">
        <xsd:restriction base="xsd:string">
            <xsd:pattern value="&aname;|&nspa;"/>
        </xsd:restriction>
    </xsd:simpleType>

    <xsd:complexType name="add">
        <xsd:complexContent mixed="true">
            <xsd:restriction base="xsd:anyType">
                <xsd:sequence>
                    <xsd:any processContents="lax" namespace="##any"
                        minOccurs="0" maxOccurs="unbounded"/>
                </xsd:sequence>
                <xsd:attribute name="sel" type="xpath-add"
                    use="required"/>
                <xsd:attribute name="pos" type="pos"/>
                <xsd:attribute name="type" type="type"/>
            </xsd:restriction>
        </xsd:complexContent>
    </xsd:complexType>

    <xsd:complexType name="replace">
        <xsd:complexContent mixed="true">
            <xsd:restriction base="xsd:anyType">
                <xsd:sequence>
                    <xsd:any processContents="lax" namespace="##any"
                        minOccurs="0" maxOccurs="1"/>



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                </xsd:sequence>
                <xsd:attribute name="sel" type="xpath" use="required"/>
            </xsd:restriction>
        </xsd:complexContent>
    </xsd:complexType>

    <xsd:simpleType name="ws">
        <xsd:restriction base="xsd:string">
            <xsd:enumeration value="before"/>
            <xsd:enumeration value="after"/>
            <xsd:enumeration value="both"/>
        </xsd:restriction>
    </xsd:simpleType>

    <xsd:complexType name="remove">
        <xsd:attribute name="sel" type="xpath" use="required"/>
        <xsd:attribute name="ws" type="ws"/>
    </xsd:complexType>

</xsd:schema>


Appendix B.  ABNF for RFC 5261

   RFC 5261 [2] does not contain an ABNF grammar for the allowed subset
   of XPath expressions, but includes an XSD-based grammar in its type
   definition for operation types (which is shown in Appendix A).  In
   order to make implementation easier, this appendix contains an ABNF
   grammar that has been derived from the XSD expressions given in RFC
   5261.  In the following grammar, "xpath" is the definition for the
   allowed XPath expressions for remove and replace operations, and
   "xpath-add" is the definition for the allowed XPath expressions for
   add operations.  The names of all grammar productions are the ones
   used in the XSD-based grammar of RFC 5261.

















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ncname     =  1*%x00-ffffffff
qname      =  [ ncname ":" ] ncname
aname      =  "@" qname
pos        =  "[" 1*DIGIT "]"
attr       =  ( "[" aname "='" 1*%x00-ffffffff "']" ) / ( "[" aname "=" DQUOTE 1*%x00-ffffffff DQUOTE "]" )
valueq     =  "[" ( qname / "." ) "=" DQUOTE 1*%x00-ffffffff DQUOTE "]"
value      =  ( "[" ( qname / "." ) "='" 1*%x00-ffffffff "']" ) / valueq
cond       =  attr / value / pos
step       =  ( qname / "*" ) 0*( cond )
piq        =  "processing-instruction(" [ DQUOTE ncname DQUOTE ] ")"
pi         =  ( "processing-instruction(" [ "'" ncname "'" ] ")" ) / piq
id         =  ( "id(" [ "'" ncname "'" ] ")" ) / ( "id(" [ DQUOTE ncname DQUOTE ] ")" )
com        =  "comment()"
text       =  "text()"
nspa       =  "namespace::" ncname
cnodes     =  ( text / com / pi ) [ pos ]
child      =  cnodes / step
last       =  child / aname / nspa
xpath      =  [ "/" ] ( ( id [ 0*( "/" step ) "/" last ] ) / ( 0*( step "/" ) last ) )
xpath-add  =  [ "/" ] ( ( id [ 0*( "/" step ) "/" child ] ) / ( 0*( step "/" ) child ) )


Author's Address

   Erik Wilde
   EMC

   Email: erik.wilde@emc.com























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