A Media Type for XML Patch Operations
draft-wilde-xml-patch-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 7351.
|
|
|---|---|---|---|
| Author | Erik Wilde | ||
| Last updated | 2013-01-16 | ||
| RFC stream | (None) | ||
| Formats | |||
| IETF conflict review | conflict-review-wilde-xml-patch, conflict-review-wilde-xml-patch, conflict-review-wilde-xml-patch, conflict-review-wilde-xml-patch, conflict-review-wilde-xml-patch, conflict-review-wilde-xml-patch | ||
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| Consensus boilerplate | Unknown | ||
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| Send notices to | (None) |
draft-wilde-xml-patch-01
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
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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
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publication of this document. Please review these documents
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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 "\[&aname;='(.)*'\]|\[&aname;="(.)*"\]">
<!ENTITY valueq "\[(&qname;|\.)="(.)*"\]">
<!ENTITY value "\[(&qname;|\.)='(.)*'\]|&valueq;">
<!ENTITY cond "&attr;|&value;|&pos;">
<!ENTITY step "(&qname;|\*)(&cond;)*">
<!ENTITY piq "processing-instruction\(("&ncname;")\)">
<!ENTITY pi "processing-instruction\(('&ncname;')?\)|&piq;">
<!ENTITY id "id\(('&ncname;')?\)|id\(("&ncname;")?\)">
<!ENTITY com "comment\(\)">
<!ENTITY text "text\(\)">
<!ENTITY nspa "namespace::&ncname;">
<!ENTITY cnodes "(&text;(&pos;)?)|(&com;(&pos;)?)|((π)(&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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