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Versions: (draft-lilley-xml-mediatypes) 00 01 02 03 04 05 06 07 08 09 10 RFC 7303

Network Working Group                                     H. S. Thompson
Internet-Draft                                   University of Edinburgh
Obsoletes: 3023 (if approved)                                  C. Lilley
Updates: 6839 (if approved)                                          W3C
Intended status: Standards Track                       November 19, 2013
Expires: May 23, 2014


                            XML Media Types
                  draft-ietf-appsawg-xml-mediatypes-05

Abstract

   This specification standardizes three media types -- application/xml,
   application/xml-external-parsed-entity, and application/xml-dtd --
   for use in exchanging network entities that are related to the
   Extensible Markup Language (XML) while defining text/xml and text/
   xml-external-parsed-entity as aliases for the respective application/
   types.  This specification also standardizes the '+xml' suffix for
   naming media types outside of these five types when those media types
   represent XML MIME entities.

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 May 23, 2014.

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
   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



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . .   3
   3.  XML Media Types . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Application/xml Registration  . . . . . . . . . . . . . .   5
     3.2.  Text/xml Registration . . . . . . . . . . . . . . . . . .   7
     3.3.  Application/xml-external-parsed-entity Registration . . .   7
     3.4.  Text/xml-external-parsed-entity Registration  . . . . . .   8
     3.5.  Application/xml-dtd Registration  . . . . . . . . . . . .   8
     3.6.  Charset considerations  . . . . . . . . . . . . . . . . .   9
   4.  The Byte Order Mark (BOM) and Charset Conversions . . . . . .  11
   5.  Fragment Identifiers  . . . . . . . . . . . . . . . . . . . .  12
   6.  The Base URI  . . . . . . . . . . . . . . . . . . . . . . . .  13
   7.  XML Versions  . . . . . . . . . . . . . . . . . . . . . . . .  13
   8.  A Naming Convention for XML-Based Media Types . . . . . . . .  14
     8.1.  Referencing . . . . . . . . . . . . . . . . . . . . . . .  15
     8.2.  +xml Structured Syntax Suffix Registration  . . . . . . .  16
   9.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  17
     9.1.  UTF-8 Charset . . . . . . . . . . . . . . . . . . . . . .  17
     9.2.  UTF-16 Charset  . . . . . . . . . . . . . . . . . . . . .  18
     9.3.  Omitted Charset and 8-bit MIME entity . . . . . . . . . .  18
     9.4.  Omitted Charset and 16-bit MIME entity  . . . . . . . . .  18
     9.5.  Omitted Charset, no Internal Encoding Declaration and
           UTF-8 Entity  . . . . . . . . . . . . . . . . . . . . . .  19
     9.6.  UTF-16BE Charset  . . . . . . . . . . . . . . . . . . . .  19
     9.7.  Non-UTF Charset . . . . . . . . . . . . . . . . . . . . .  20
     9.8.  Omitted Charset with Internal Encoding Declaration  . . .  20
     9.9.  INCONSISTENT EXAMPLE: Conflicting Charset and Internal
           Encoding Declaration  . . . . . . . . . . . . . . . . . .  20
     9.10. INCONSISTENT EXAMPLE: Conflicting Charset and BOM . . . .  21
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  21
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  23
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  23
     12.2.  Informative References . . . . . . . . . . . . . . . . .  25
   Appendix A.  Why Use the '+xml' Suffix for XML-Based MIME Types?   26
   Appendix B.  Changes from RFC 3023  . . . . . . . . . . . . . . .  26
   Appendix C.  Acknowledgements . . . . . . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27





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1.  Introduction

   The World Wide Web Consortium has issued the Extensible Markup
   Language (XML) 1.0 [XML] and Extensible Markup Language (XML) 1.1
   [XML1.1] specifications.  To enable the exchange of XML network
   entities, this specification standardizes three media types --
   application/xml, application/xml-external-parsed-entity, and
   application/xml-dtd and two aliases -- text/xml and text/xml-
   external-parsed-entity, as well as a naming convention for
   identifying XML-based MIME media types (using '+xml').

   XML has been used as a foundation for other media types, including
   types in every branch of the IETF media types tree.  To facilitate
   the processing of such types, and in line with the recognition in
   [RFC6838] of structured syntax name suffixes, a suffix of '+xml' is
   described in Section 8.  This will allow generic XML-based tools --
   browsers, editors, search engines, and other processors -- to work
   with all XML-based media types.

   This specification replaces [RFC3023].  Major differences are in the
   areas of alignment of charset handling for text/xml and text/xml-
   external-parsed-entity with application/xml, the addition of XPointer
   and XML Base as fragment identifiers and base URIs, respectively,
   integration of the XPointer Registry and updating of many references.

2.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   specification are to be interpreted as described in [RFC2119].

   As defined in [RFC2781] (informative), the three character sets
   "utf-16", "utf-16le", and "utf-16be" are used to label UTF-16 text.
   In this specification, "the UTF-16 family" refers to those three
   character sets.  By contrast, the phrases "utf-16" or UTF-16 in this
   specification refer specifically to the single charset "utf-16".

   As sometimes happens between two communities, both MIME and XML have
   defined the term entity, with different meanings.  Section 2.4 of
   [RFC2045] says:

      "The term 'entity' refers specifically to the MIME-defined header
      fields and contents of either a message or one of the parts in the
      body of a multipart entity."

   Section 4 of [XML] says:





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      "An XML document may consist of one or many storage units.  These
      are called entities; they all have content and are all (except for
      the document entity and the external DTD subset) identified by
      entity name".

   In this specification, "XML MIME entity" is defined as the latter (an
   XML entity) encapsulated in the former (a MIME entity).

   Furthermore, XML provides for the naming and referencing of entities
   for purposes of inclusion and/or substitution.  In this specification
   "XML-entity declaration/reference/..." is used to avoid confusion
   when referring to such cases.

3.  XML Media Types

   Registration information for media types for use with XML MIME
   entities is described in the sections below.  Within the XML
   specification, such entities can be classified into four types.  In
   the XML terminology, they are called "document entities", "external
   DTD subsets", "external parsed entities", and "external parameter
   entities".  Appropriate usage for the types registered below is as
   follows:

   document entities  The media types application/xml or text/xml MAY be
      used.

   external DTD subsets  The media type application/xml-dtd SHOULD be
      used.  The media types application/xml and text/xml MUST NOT be
      used.

   external parsed entities  The media types application/xml-external-
      parsed-entity or text/xml-external-parsed-entity SHOULD be used.
      The media types application/xml and text/xml MUST NOT be used
      unless the parsed entities are also well-formed "document
      entities" and are referenced as such.

   external parameter entities  The media type application/xml-dtd
      SHOULD be used.  The media types application/xml and text/xml MUST
      NOT be used.

      Note that [RFC3023] (which this specification obsoletes)
      recommended the use of text/xml and text/xml-external-parsed-
      entity for document entities and external parsed entities,
      respectively, but described charset handling which differed from
      common implementation practice.  These media types are still
      commonly used, and this specification aligns the charset handling
      with industry practice.




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      Note that [RFC2376] (which is obsolete) allowed application/xml
      and text/xml to be used for any of the four types, although in
      practice it is likely to have been rare.

   Neither external DTD subsets nor external parameter entities parse as
   XML documents, and while some XML document entities may be used as
   external parsed entities and vice versa, there are many cases where
   the two are not interchangeable.  XML also has unparsed entities,
   internal parsed entities, and internal parameter entities, but they
   are not XML MIME entities.

   Compared to [RFC2376] or [RFC3023], this specification alters the
   charset handling of text/xml and text/xml-external-parsed-entity,
   treating them no differently from the respective application/ types,
   however application/xml and application/xml-external-parsed-entity
   are still RECOMMENDED, to avoid possible confusion based on the
   earlier distinction.  The former confusion around the question of
   default character sets for the text/xml... types has been resolved by
   [HTTPbis] changing [RFC2616] by removing the ISO-8859-1 default and
   not defining any default at all, as well as [RFC6657] updating
   [RFC2046] to remove the US-ASCII default.  See Section 3.6 for the
   now-unified approach to the charset parameter which results.

   XML provides a general framework for defining sequences of structured
   data.  It is often appropriate to define new media types that use XML
   but define a specific application of XML, due to domain-specific
   display, editing, security considerations or runtime information.
   Furthermore, such media types may allow only UTF-8 and/or UTF-16 and
   prohibit other character sets.  This specification does not prohibit
   such media types and in fact expects them to proliferate.  However,
   developers of such media types are RECOMMENDED to use this
   specification as a basis for their registration.  See Section 8 for
   more detailed recommendations on using the '+xml' suffix for
   registration of such media types.

   An XML document labeled as application/xml or text/xml, or with a
   '+xml' media type, might contain namespace declarations, stylesheet-
   linking processing instructions (PIs), schema information, or other
   declarations that might be used to suggest how the document is to be
   processed.  For example, a document might have the XHTML namespace
   and a reference to a CSS stylesheet.  Such a document might be
   handled by applications that would use this information to dispatch
   the document for appropriate processing.

3.1.  Application/xml Registration

   Type name:  application




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   Subtype name:  xml

   Required parameters:  none

   Optional parameters:  charset

      See Section 3.6.

   Encoding considerations:  Depending on the charset encoding used, XML
      MIME entities can consist of 7bit, 8bit or binary data [RFC6838].
      For 7-bit transports, 7bit data, for example data with charset
      encoding US-ASCII, does not require content-transfer-encoding, but
      8bit or binary data, for example data with charset encoding UTF-8
      or UTF-16, MUST be content-transfer-encoded in quoted-printable or
      base64.  For 8-bit clean transport (e.g.  8BITMIME ESMTP [RFC6152]
      or NNTP [RFC3977]), 7bit or 8bit data, for example data with
      charset encoding UTF-8 or US-ASCII, does not require content-
      transfer-encoding, but binary data, for example data with a
      charset encoding from the UTF-16 family, MUST be content-transfer-
      encoded in base64.  For binary clean transports (e.g.  BINARY
      ESMTP [RFC3030] or HTTP [HTTPbis]), no content-transfer-encoding
      is necessary (or even possible, in the case of HTTP) for 7bit,
      8bit or binary data.

   Security considerations:  See Section 11.

   Interoperability considerations:  XML has proven to be interoperable
      across both generic and task-specific applications and for import
      and export from multiple XML authoring and editing tools.
      Validating processors provide maximum interoperability.  Although
      non-validating processors may be more efficient, they are not
      required to handle all features of XML.  For further information,
      see sub-section 2.9 "Standalone Document Declaration" and section
      5 "Conformance" of [XML] .

   Published specification:  Extensible Markup Language (XML) 1.0 (Fifth
      Edition) [XML] or subsequent editions or versions thereof.

   Applications that use this media type:  XML is device-, platform-,
      and vendor-neutral and is supported by a wide range of generic XML
      tools (editors, parsers, Web agents, ...), generic and task-
      specific applications.

   Additional information:

      Magic number(s):  None.





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         Although no byte sequences can be counted on to always be
         present, XML MIME entities in ASCII-compatible character sets
         (including UTF-8) often begin with hexadecimal 3C 3F 78 6D 6C
         ("<?xml"), and those in UTF-16 often begin with hexadecimal FE
         FF 00 3C 00 3F 00 78 00 6D 00 6C or FF FE 3C 00 3F 00 78 00 6D
         00 6C 00 (the Byte Order Mark (BOM) followed by "<?xml").  For
         more information, see Appendix F of [XML].

      File extension(s):  .xml

      Macintosh File Type Code(s):  "TEXT"

      Base URI:  See Section 6

   Person and email address for further information:  See Authors'
      Addresses section

   Intended usage:  COMMON

   Author:  See Authors' Addresses section

   Change controller:  The XML specification is a work product of the
      World Wide Web Consortium's XML Core Working Group.  The W3C has
      change control over this specification.

3.2.  Text/xml Registration

   text/xml is an alias for application/xml, as defined in Section 3.1
   above.

3.3.  Application/xml-external-parsed-entity Registration

   Type name:  application

   Subtype name:  xml-external-parsed-entity

   Required parameters:  none

   Optional parameters:  charset

      See Section 3.6.

   Encoding considerations:  Same as application/xml as described in
      Section 3.1.

   Security considerations:  See Section 11.





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   Interoperability considerations:  XML external parsed entities are as
      interoperable as XML documents, though they have a less tightly
      constrained structure and therefore need to be referenced by XML
      documents for proper handling by XML processors.  Similarly, XML
      documents cannot be reliably used as external parsed entities
      because external parsed entities are prohibited from having
      standalone document declarations or DTDs.  Identifying XML
      external parsed entities with their own content type should
      enhance interoperability of both XML documents and XML external
      parsed entities.

   Published specification:  Same as application/xml as described in
      Section 3.1.

   Applications which use this media type:  Same as application/xml as
      described in Section 3.1.

   Additional information:

      Magic number(s):  Same as application/xml as described in
            Section 3.1.

      File extension(s):  .xml or .ent

      Macintosh File Type Code(s):  "TEXT"

      Base URI:  See Section 6

   Person and email address for further information:  See Authors'
      Addresses section.

   Intended usage:  COMMON

   Author:  See Authors' Addresses section.

   Change controller:  The XML specification is a work product of the
      World Wide Web Consortium's XML Core Working Group.  The W3C has
      change control over this specification.

3.4.  Text/xml-external-parsed-entity Registration

   text/xml-external-parsed-entity is an alias for application/xml-
   external-parsed-entity, as defined in Section 3.3 above.

3.5.  Application/xml-dtd Registration

   Type name:  application




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   Subtype name:  xml-dtd

   Required parameters:  none

   Optional parameters:  charset

      See Section 3.6.

   Encoding considerations:  Same as Section 3.1.

   Security considerations:  See Section 11.

   Interoperability considerations:  XML DTDs have proven to be
      interoperable by DTD authoring tools and XML validators, among
      others.

   Published specification:  Same as application/xml as described in
      Section 3.1.

   Applications which use this media type:  DTD authoring tools handle
      external DTD subsets as well as external parameter entities.  XML
      validators may also access external DTD subsets and external
      parameter entities.

   Additional information:

      Magic number(s):  Same as application/xml as described in
            Section 3.1.

      File extension(s):  .dtd or .mod

      Macintosh File Type Code(s):  "TEXT"

   Person and email address for further information:  See Authors'
      Addresses section.

   Intended usage:  COMMON

   Author:  See Authors' Addresses section.

   Change controller:  The XML specification is a work product of the
      World Wide Web Consortium's XML Core Working Group.  The W3C has
      change control over this specification.

3.6.  Charset considerations

   As many as three distinct sources of information about character
   encoding may be present for an XML MIME entity: a charset parameter,



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   a Byte Order Mark (BOM -- see Section 4 below) and an XML encoding
   declaration (see Section 4.3.3 of [XML]).  Ensuring consistency among
   these sources requires coordination between entity authors and MIME
   agents (that is, processes which package, transfer, deliver and/or
   receive MIME entities).  Some MIME agents will be what we will call
   "XML-aware", that is, capable of processing XML MIME entities and
   detecting the XML encoding declaration (or its absence).  Others will
   not be XML-aware, and thus cannot know anything about the XML
   encoding declaration.  Some MIME agents, such as proxies and
   transcoders, both consume and produce MIME entities.

   XML-aware MIME producers SHOULD supply a charset parameter and/or an
   appropriate BOM with non-UTF-8-encoded XML MIME entities which lack
   an encoding declaration, and SHOULD remove or correct an encoding
   declaration which is known to be incorrect (for example, as a result
   of transcoding).

   XML-unaware MIME producers MUST NOT supply a charset parameter with
   an XML MIME entity unless the entity's character encoding is reliably
   known.

   XML MIME producers are RECOMMENDED to provide means for XML MIME
   entity authors to control the supply of charset parameters for their
   entities, for example by enabling user-level configuration of
   filename-to-Content-Type-header mappings on a file-by-file or suffix
   basis.

   For XML MIME consumers, the question of priority arises in cases when
   the available character encoding information is not consistent.
   Again, we must distinguish betweeen XML-aware and XML-unaware
   processors.

   When a charset parameter is specified for an XML MIME entity, then
   regardless of whether or not the entity contains in-band encoding
   information, that is, either a BOM (Section 4) or an XML encoding
   declaration or both, or none, the normative component of the [XML]
   specification leaves the question open as to how to determine the
   encoding with which to attempt to process the entity.  In particular,
   in the case where there is in-band information and it conflicts with
   the charset parameter, the [XML] specification does not specify which
   should be taken to be authoritative.  In its (non-normative)
   Appendix F it defers to this specification:

      [T]he preferred method of handling conflict should be specified as
      part of the higher-level protocol used to deliver XML.  In
      particular, please refer to [IETF RFC 3023] or its successor...





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   Accordingly, to conform with deployed processors and content and to
   avoid conflicting with this or other normative specifications, this
   specification sets the priority as follows:

   All consumers SHOULD treat a BOM (Section 4) as authoritative if it
   is present in an XML MIME entity.  In the absence of a BOM
   (Section 4), all consumers SHOULD treat the charset parameter as
   authoritative if it is present.  For XML-aware consumers, note that
   Section 4.3.3 of the [XML] specification does _not_ make it an error
   for the charset parameter and the XML encoding declaration (or the
   UTF-8 default in the absence of encoding declaration and BOM) to be
   inconsistent, although such processors might choose to issue a
   warning in this case.

   When MIME producers conform to the requirements on them stated above,
   such inconsistencies will not arise---this statement of priorities
   only has practical impact in the case of non-conforming XML MIME
   entities.

   If an XML MIME entity is received where the charset parameter is
   omitted, no information is being provided about the charset by the
   MIME Content-Type header.  XML-aware processors MUST follow the
   requirements in section 4.3.3 of [XML] that directly address this
   case.  XML-unaware MIME processors SHOULD NOT assume a default
   charset in this case.

4.  The Byte Order Mark (BOM) and Charset Conversions

   Section 4.3.3 of [XML] specifies that XML MIME entities in the
   charset "utf-16" MUST begin with a byte order mark (BOM), which is a
   hexadecimal octet sequence 0xFE 0xFF (or 0xFF 0xFE, depending on
   endianness).  The XML Recommendation further states that the BOM is
   an encoding signature, and is not part of either the markup or the
   character data of the XML document.

   Due to the presence of the BOM, applications that convert XML from
   "utf-16" to an encoding other than "utf-8" MUST strip the BOM before
   conversion.  Similarly, when converting from another encoding into
   "utf-16", the BOM MUST be added after conversion is complete unless
   the original encoding was "utf-8" and a BOM was already present, in
   which case it will have been transcoded into a "utf-16" BOM already.

   Section 4.3.3 of [XML] also allows for XML MIME entities in the
   charset "utf-8" to begin with a byte order mark (BOM), which is a
   hexadecimal octet sequence 0xEF 0xBB 0xBF, also defined to be an
   encoding signature, and not part of either the markup or the
   character data of the XML document.




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   Applications that convert XML from "utf-8" to an encoding other than
   "utf-16" MUST strip the BOM, if present, before conversion.
   Applications which convert XML into "utf-8" SHOULD add a BOM after
   conversion is complete.

   In addition to the charset "utf-16", [RFC2781] introduces "utf-16le"
   (little endian) and "utf-16be" (big endian) as well.  The BOM is
   prohibited for these character sets.  When an XML MIME entity is
   encoded in "utf-16le" or "utf-16be", it MUST NOT begin with the BOM
   but SHOULD contain an in-band XML encoding declaration.  Conversion
   from "utf-16"or "utf-8" to "utf-16be" or "utf-16le" and conversion in
   the other direction MUST strip or add the appropriate BOM,
   respectively.

5.  Fragment Identifiers

   Uniform Resource Identifiers (URIs) can contain fragment identifiers
   (see Section 3.5 of [RFC3986]).  Specifying the syntax and semantics
   of fragment identifiers is devolved by [RFC3986] to the appropriate
   media type registration.

   The syntax and semantics of fragment identifiers for the XML media
   types defined in this specification are based on the
   [XPointerFramework] W3C Recommendation.  It allows simple names, and
   more complex constructions based on named schemes.  When the syntax
   of a fragment identifier part of any URI or IRI with a retrieved
   media type governed by this specification conforms to the syntax
   specified in [XPointerFramework], conforming applications MUST
   interpret such fragment identifiers as designating whatever is
   specified by the [XPointerFramework] together with any other
   specifications governing the XPointer schemes used in those
   identifiers which the applications support.  Conforming applications
   MUST support the 'element' scheme as defined in [XPointerElement],
   but need not support other schemes.

   If an XPointer error is reported in the attempt to process the part,
   this specification does not define an interpretation for the part.

   A registry of XPointer schemes [XPtrReg] is maintained at the W3C.
   Document authors SHOULD NOT use unregistered schemes.  Scheme authors
   SHOULD register their schemes ([XPtrRegPolicy] describes requirements
   and procedures for doing so).

   See Section 8.1 for additional requirements which apply when an XML-
   based media type follows the naming convention '+xml'.






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   If [XPointerFramework] and [XPointerElement] are inappropriate for
   some XML-based media type, it SHOULD NOT follow the naming convention
   '+xml'.

   When a URI has a fragment identifier, it is encoded by a limited
   subset of the repertoire of US-ASCII [ASCII] characters, as defined
   in [RFC3986].

6.  The Base URI

   Section 5.1 of [RFC3986] specifies that the semantics of a relative
   URI reference embedded in a MIME entity is dependent on the base URI.
   The base URI is established by (1) the base URI embedded in content,
   (2) the base URI from the encapsulating entity, (3) the base URI from
   the Retrieval URI, or (4) the default base URI, in order of
   precedence.  [RFC3986] further specifies that the mechanism for
   embedding the base URI is dependent on the media type.

   This specification accordingly provides the following media type
   dependent mechanism for embedding the base URI in a MIME entity of
   type application/xml, text/xml, application/xml-external-parsed-
   entity or text/xml-external-parsed-entity: An XML MIME entity MAY use
   the xml:base attribute, as described in detail in [XMLBase], to
   establish a base URI for that entity.

   Note that the base URI itself might be embedded in a different MIME
   entity, since the default value for the xml:base attribute can be
   specified in an external DTD subset or external parameter entity.
   Since conforming XML processors need not always read and process
   external entities, the effect of such an external default is
   uncertain and therefore its use is NOT RECOMMENDED.

7.  XML Versions

   application/xml, application/xml-external-parsed-entity, and
   application/xml-dtd, text/xml and text/xml-external-parsed-entity are
   to be used with [XML].  In all examples herein where version="1.0" is
   shown, it is understood that version="1.1" might also appear,
   providing the content does indeed conform to [XML1.1].

   The normative requirement of this specification upon XML documents
   and processors is to follow the requirements of [XML], section 4.3.3.
   Except for minor clarifications, that section is substantially
   identical from the first edition to the current (5th) edition of XML
   1.0, and for XML 1.1 1st or 2nd edition [XML1.1].  Therefore,
   references herein to [XML] may be interpreted as referencing any
   existing version or edition of XML, or any subsequent edition or
   version which makes no incompatible changes to that section.



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   Specifications and recommendations based on or referring to this RFC
   SHOULD indicate any limitations on the particular versions or
   editions of XML to be used.

8.  A Naming Convention for XML-Based Media Types

   This section supersedes the earlier registration of the '+xml' suffix
   [RFC6839].

   This specification recommends the use of a naming convention (a
   suffix of '+xml') for identifying XML-based media types, in line with
   the recognition in [RFC6838] of structured syntax name suffixes.
   This allows the use of generic XML processors and technologies on a
   wide variety of different XML document types at a minimum cost, using
   existing frameworks for media type registration.

   When a new media type is introduced for an XML-based format, the name
   of the media type SHOULD end with '+xml' unless generic XML
   processing is in some way inappropriate for documents of the new
   type.  This convention will allow applications that can process XML
   generically to detect that the MIME entity is supposed to be an XML
   document, verify this assumption by invoking some XML processor, and
   then process the XML document accordingly.  Applications may match
   for types that represent XML MIME entities by comparing the subtype
   to the pattern '*/*+xml'.  (However note that 4 of the 5 media types
   defined in this specification -- text/xml, application/xml, text/xml-
   external-parsed-entity, and application/xml-external-parsed-entity --
   also represent XML MIME entities while not conforming to the '*/
   *+xml' pattern.)

      NOTE: Section 5.3.2HTTPbis [HTTPbis] does not support Accept
      headers of the form "Accept: */*+xml" and so this header MUST NOT
      be used in this way.

   Media types following the naming convention '+xml' SHOULD introduce
   the charset parameter for consistency, since XML-generic processing
   applies the same program for any such media type.  However, there are
   some cases that the charset parameter need not be introduced.  For
   example:

      When an XML-based media type is restricted to UTF-8, it is not
      necessary to introduce the charset parameter.  "UTF-8 only" is a
      generic principle and UTF-8 is the default of XML.

      When an XML-based media type is restricted to UTF-8 and UTF-16, it
      might not be unreasonable to omit the charset parameter.  Neither
      UTF-8 nor UTF-16 require in-band XML encoding declarations.




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   XML generic processing is not always appropriate for XML-based media
   types.  For example, authors of some such media types may wish that
   the types remain entirely opaque except to applications that are
   specifically designed to deal with that media type.  By NOT following
   the naming convention '+xml', such media types can avoid XML-generic
   processing.  Since generic processing will be useful in many cases,
   however -- including in some situations that are difficult to predict
   ahead of time -- the '+xml' convention is to be preferred unless
   there is some particularly compelling reason not to.

   The registration process for specific '+xml' media types is described
   in [RFC6838].  The registrar for the IETF tree will encourage new
   XML-based media type registrations in the IETF tree to follow this
   guideline.  Registrars for other trees SHOULD follow this convention
   in order to ensure maximum interoperability of their XML-based
   documents.  Similarly, media subtypes that do not represent XML MIME
   entities MUST NOT be allowed to register with a '+xml' suffix.

   In addition to the changes described above, the change controller has
   been changed to be the World Wide Web Consortium (W3C).

8.1.  Referencing

   Registrations for new XML-based media types under top-level types
   SHOULD, in specifying the charset parameter and encoding
   considerations, define them as: "Same as [charset parameter /
   encoding considerations] of application/xml as specified in RFC
   XXXX."

   Enabling the charset parameter is RECOMMENDED, since this information
   can be used by XML processors to determine authoritatively the
   charset of the XML MIME entity in the absence of a BOM.  If there are
   some reasons not to follow this advice, they SHOULD be included as
   part of the registration.  As shown above, two such reasons are
   "UTF-8 only" or "UTF-8 or UTF-16 only".

   These registrations SHOULD specify that the XML-based media type
   being registered has all of the security considerations described in
   RFC XXXX plus any additional considerations specific to that media
   type.

   These registrations SHOULD also make reference to RFC XXXX in
   specifying magic numbers, base URIs, and use of the BOM.

   These registrations MAY reference the application/xml registration in
   RFC XXXX in specifying interoperability considerations, if these
   considerations are not overridden by issues specific to that media
   type.



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8.2.  +xml Structured Syntax Suffix Registration

   Name:  Extensible Markup Language (XML)

   +suffix:  +xml

   Reference:  This specification

   Encoding considerations:  Same as Section 3.1.

   Fragment identifier considerations:  Registrations which use this
      '+xml' convention MUST also make reference to RFC XXXX,
      specifically Section 5, in specifying fragment identifier syntax
      and semantics, and they MAY restrict the syntax to a specified
      subset of schemes, except that they MUST NOT disallow barenames or
      'element' scheme pointers.  They MAY further require support for
      other registered schemes.  They also MAY add additional syntax
      (which MUST NOT overlap with [XPointerFramework] syntax) together
      with associated semantics, and MAY add additional semantics for
      barename XPointers which, as provided for in Section 5, will only
      apply when this specification does not define an interpretation.



         In practice these constraints imply that for a fragment
         identifier addressed to an instance of a specific "xxx/yyy+xml"
         type, there are three cases:

            For fragment identifiers matching the syntax defined in
            [XPointerFramework], where the fragment identifier resolves
            per the rules specified there, then process as specified
            there;

            For fragment identifiers matching the syntax defined in
            [XPointerFramework], where the fragment identifier does
            _not_ resolve per the rules specified there, then process as
            specified in "xxx/yyy+xml";

            For fragment identifiers _not_ matching the syntax defined
            in [XPointerFramework], then process as specified in "xxx/
            yyy+xml".  A fragment identifier of the form
            "xywh=160,120,320,240", as defined in [MediaFrags], which
            might be used in a URI for an XML-encoded image, would fall
            in this category.

   Interoperability considerations:  Same as Section 3.1.  See above,
      and also Section 3.6, for guidelines on the use of the 'charset'
      parameter.



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   Security considerations:  See Section 11.

   Contact:  See Authors' Addresses section.

   Author:  See Authors' Addresses section.

   Change controller:  The XML specification is a work product of the
      World Wide Web Consortium's XML Core Working Group.  The W3C has
      change control over this specification.

9.  Examples

   The examples below give the charset portion, if any, of the value of
   the MIME Content-type header and the XML declaration or Text
   declaration (which includes the encoding declaration) inside the XML
   MIME entity.  For UTF-16 examples, the Byte Order Mark character
   appropriately UTF-16-encoded is denoted as "{BOM}", and the XML or
   Text declaration is assumed to come at the beginning of the XML MIME
   entity, immediately following the encoded BOM.  Note that other MIME
   headers may be present, and the XML MIME entity may contain other
   data in addition to the XML declaration; the examples focus on the
   Content-type header and the encoding declaration for clarity.

   All the examples below apply to all five media types declared above
   in Section 3, as well as to any media types declared using the '+xml'
   convention (with the exception of the examples involving the charset
   parameter for any such media types which do not enable its use).  See
   the XML MIME entities table (Section 3, Paragraph 2) for discussion
   of which types are appropriate for which varieties of XML MIME
   entities.

   This section is non-normative.  In particular, note that all
   [RFC2119] language herein reproduces or summarizes the consequences
   of normative statements already made above, and has no independent
   normative force, and accordingly does not appear in uppercase.

9.1.  UTF-8 Charset

   Content-type charset: charset="utf-8"

   <?xml version="1.0" encoding="utf-8"?>

   This is the recommended encoding for use with all the media types
   defined in this specification.  Since the charset parameter is
   provided and there is no BOM, both MIME and XML processors must treat
   the enclosed entity as UTF-8 encoded.





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   If sent using a 7-bit transport (e.g.  SMTP [RFC5321]), the XML MIME
   entity must use a content-transfer-encoding of either quoted-
   printable or base64.  For an 8-bit clean transport (e.g.  8BITMIME
   ESMTP or NNTP), or a binary clean transport (e.g.  BINARY ESMTP or
   HTTP), no content-transfer-encoding is necessary (or even possible,
   in the case of HTTP).

9.2.  UTF-16 Charset

   Content-type charset: charset="utf-16"

   {BOM}<?xml version="1.0" encoding="utf-16"?>

   or

   {BOM}<?xml version="1.0"?>

   For application/... cases, if sent using a 7-bit transport (e.g.
   SMTP) or an 8-bit clean transport (e.g.  8BITMIME ESMTP or NNTP), the
   XML MIME entity must be encoded in quoted-printable or base64; for a
   binary clean transport (e.g.  BINARY ESMTP or HTTP), no content-
   transfer-encoding is necessary (or even possible, in the case of
   HTTP).

   As described in [RFC2781], the UTF-16 family must not be used with
   media types under the top-level type "text" except over HTTP or HTTPS
   (see section A.2 of HTTP [HTTPbis] for details).  Hence this example
   is only possible in text/... cases when the XML MIME entity is
   transmitted via HTTP or HTTPS, which use a MIME-like mechanism and
   are binary-clean protocols, hence do not perform CR and LF
   transformations and allow NUL octets.  Since HTTP is binary clean, no
   content-transfer-encoding is necessary (or even possible).

9.3.  Omitted Charset and 8-bit MIME entity

   Content-type charset: [none]

   <?xml version="1.0" encoding="iso-8859-1"?>

   Since the charset parameter is not provided in the Content-Type
   header and there is no BOM, XML processors must treat the
   "iso-8859-1" encoding as authoritative.  XML-unaware MIME processors
   should make no assumptions about the charset of the XML MIME entity.

9.4.  Omitted Charset and 16-bit MIME entity

   Content-type charset: [none]




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   {BOM}<?xml version="1.0" encoding="utf-16"?>

   or

   {BOM}<?xml version="1.0"?>

   This example shows a 16-bit MIME entity with no charset parameter.
   However since there is a BOM all processors must treat the entity as
   UTF-16-encoded.

   Omitting the charset parameter is not recommended for application/...
   when used with transports other than HTTP or HTTPS.  text/... should
   not be used for 16-bit MIME with transports other than HTTP or HTTPS
   (see discussion above (Section 9.2, Paragraph 6)).

9.5.  Omitted Charset, no Internal Encoding Declaration and UTF-8 Entity

   Content-type charset: [none]

   <?xml version='1.0'?>

   In this example, the charset parameter has been omitted, there is no
   internal encoding declaration, and there is no BOM.  Since there is
   no BOM or charset parameter, the XML processor follows the
   requirements in section 4.3.3, and optionally applies the mechanism
   described in Appendix F (which is non-normative) of [XML] to
   determine the charset encoding of UTF-8.  Although the XML MIME
   entity does not contain an encoding declaration, the encoding
   actually _is_ UTF-8, so this is still a conforming XML MIME entity.

   An XML-unaware MIME processor should make no assumptions about the
   charset of the XML MIME entity.

   See Section 9.1 for transport-related issues for UTF-8 XML MIME
   entities.

9.6.  UTF-16BE Charset

   Content-type charset: charset="utf-16be"

   <?xml version='1.0' encoding='utf-16be'?>

   Observe that the BOM does not exist.  Since the charset parameter is
   provided and there is no BOM, MIME and XML processors must treat the
   enclosed entity as UTF-16BE encoded.

   See also the additional considerations in the UTF-16 example
   (Section 9.2) above.



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9.7.  Non-UTF Charset

   Content-type charset: charset="iso-2022-kr"

   <?xml version="1.0" encoding="iso-2022-kr"?>

   This example shows the use of a non-UTF charset (in this case Hangul,
   but this example is intended to cover all non-UTF-family character
   sets).  Since the charset parameter is provided and there is no BOM,
   all processors must treat the enclosed entity as encoded per RFC
   1557.

   Since ISO-2022-KR [RFC1557] has been defined to use only 7 bits of
   data, no content-transfer-encoding is necessary with any transport:
   for character sets needing 8 or more bits, considerations such as
   those discussed above (Section 9.1, Section 9.2) would apply.

9.8.  Omitted Charset with Internal Encoding Declaration

   Content-type charset: [none]

   <?xml version='1.0' encoding="iso-10646-ucs-4"?>

   In this example, the charset parameter has been omitted, and there is
   no BOM.  However, the XML MIME entity does have an encoding
   declaration inside the XML MIME entity that specifies the entity's
   charset.  Following the requirements in section 4.3.3, and optionally
   applying the mechanism described in Appendix F (non-normative) of
   [XML], the XML processor determines the charset encoding of the XML
   MIME entity (in this example, UCS-4).

   An XML-unaware MIME processor should make no assumptions about the
   charset of the XML MIME entity.

   For character sets needing 8 or more bits, considerations such as
   those discussed above (Section 9.1, Section 9.2) would apply

9.9.  INCONSISTENT EXAMPLE: Conflicting Charset and Internal Encoding
      Declaration

   Content-type charset: charset="iso-8859-1"

   <?xml version="1.0" encoding="utf-8"?>

   Although the charset parameter is provided in the Content-Type header
   and there is no BOM and the charset parameter differs from the XML
   encoding declaration, MIME and XML processors will interoperate.
   Since the charset parameter is authoritative in the absence of a BOM,



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   all processors will treat the enclosed entity as iso-8859-1 encoded.
   That is, the "UTF-8" encoding declaration will be ignored.

   Processors generating XML MIME entities must not label conflicting
   charset information between the MIME Content-Type and the XML
   declaration unless they have definitive information about the actual
   encoding, for example as a result of systematic transcoding.  In
   particular, the addition by servers of an explicit, site-wide charset
   default has frequently lead to interoperability problems for XML
   documents.

9.10.  INCONSISTENT EXAMPLE: Conflicting Charset and BOM

   Content-type charset: charset="iso-8859-1"

   {BOM}<?xml version="1.0"?>

   Although the charset parameter is provided in the Content-Type
   header, there is a BOM, so MIME and XML processors may not
   interoperate.  Since the BOM parameter is authoritative for XML
   processors, they will treat the enclosed entity as UTF-16-encoded.
   That is, the "iso-8859-1" charset parameter will be ignored.  XML-
   unaware MIME processors on the other hand may be unaware of the BOM
   and so treat the entity as encoded in iso-8859-1.

   Processors generating XML MIME entities must not label conflicting
   charset information between the MIME Content-Type and an entity-
   initial BOM.

10.  IANA Considerations

   As described in Section 8, this specification updates the [RFC6839]
   registration for XML-based MIME types (the "+xml" types).

11.  Security Considerations

   XML MIME entities contain information which may be parsed and further
   processed by the recipient.  These entities may contain, and
   recipients may permit, explicit system level commands to be executed
   while processing the data.  To the extent that a recipient
   application executes arbitrary command strings from within XML MIME
   entities, they may be at risk.

   In general, any information stored outside of the direct control of
   the user -- including CSS style sheets, XSL transformations, XML-
   entity declarations, and DTDs -- can be a source of insecurity, by
   either obvious or subtle means.  For example, a tiny "whiteout
   attack" modification made to a "master" style sheet could make words



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   in critical locations disappear in user documents, without directly
   modifying the user document or the stylesheet it references.  Thus,
   the security of any XML document is vitally dependent on all of the
   documents recursively referenced by that document.

   The XML-entity lists and DTDs for XHTML 1.0 [XHTML], for instance,
   are likely to be a commonly used set of information.  Many developers
   will use and trust them, few of whom will know much about the level
   of security on the W3C's servers, or on any similarly trusted
   repository.

   The simplest attack involves adding declarations that break
   validation.  Adding extraneous declarations to a list of character
   XML-entities can effectively "break the contract" used by documents.
   A tiny change that produces a fatal error in a DTD could halt XML
   processing on a large scale.  Extraneous declarations are fairly
   obvious, but more sophisticated tricks, like changing attributes from
   being optional to required, can be difficult to track down.  Perhaps
   the most dangerous option available to attackers, when external DTD
   subsets or external parameter entities or other externally-specified
   defaulting is involved, is redefining default values for attributes:
   e.g.  if developers have relied on defaulted attributes for security,
   a relatively small change might expose enormous quantities of
   information.

   Apart from the structural possibilities, another option, "XML-entity
   spoofing," can be used to insert text into documents, vandalizing and
   perhaps conveying an unintended message.  Because XML permits
   multiple XML-entity declarations, and the first declaration takes
   precedence, it is possible to insert malicious content where an XML-
   entity reference is used, such as by inserting the full text of
   Winnie the Pooh in place of every occurrence of &mdash;.

   Security considerations will vary by domain of use.  For example, XML
   medical records will have much more stringent privacy and security
   considerations than XML library metadata.  Similarly, use of XML as a
   parameter marshalling syntax necessitates a case by case security
   review.

   XML may also have some of the same security concerns as plain text.
   Like plain text, XML can contain escape sequences that, when
   displayed, have the potential to change the display processor
   environment in ways that adversely affect subsequent operations.
   Possible effects include, but are not limited to, locking the
   keyboard, changing display parameters so subsequent displayed text is
   unreadable, or even changing display parameters to deliberately
   obscure or distort subsequent displayed material so that its meaning
   is lost or altered.  Display processors SHOULD either filter such



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   material from displayed text or else make sure to reset all important
   settings after a given display operation is complete.

   Some terminal devices have keys whose output, when pressed, can be
   changed by sending the display processor a character sequence.  If
   this is possible the display of a text object containing such
   character sequences could reprogram keys to perform some illicit or
   dangerous action when the key is subsequently pressed by the user.
   In some cases not only can keys be programmed, they can be triggered
   remotely, making it possible for a text display operation to directly
   perform some unwanted action.  As such, the ability to program keys
   SHOULD be blocked either by filtering or by disabling the ability to
   program keys entirely.

   Note that it is also possible to construct XML documents that make
   use of what XML terms "[XML-]entity references" to construct repeated
   expansions of text.  Recursive expansions are prohibited by [XML] and
   XML processors are required to detect them.  However, even non-
   recursive expansions may cause problems with the finite computing
   resources of computers, if they are performed many times.  For
   example, consider the case where XML-entity A consists of 100 copies
   of XML-entity B, which in turn consists of 100 copies of XML-entity
   C, and so on.

12.  References

12.1.  Normative References

   [HTTPbis]  Fielding, R., "Hypertext Transfer Protocol (HTTP/1.1)
              [revised]", ietf-httpbis-p2-semantics (work in progress),
              September 2013.

   [RFC2045]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part One: Format of Internet Message
              Bodies", RFC 2045, November 1996.

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              November 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2781]  Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO
              10646", RFC 2781, February 2000.






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   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifiers (URI): Generic Syntax.", RFC 3986,
              January 2005.

   [RFC6657]  Melnikov, A. and J. Reschke, "Update to MIME regarding
              "charset" Parameter Handling in Textual Media Types", RFC
              6657, July 2012,
              <http://www.rfc-editor.org/rfc/rfc6657.txt>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13, RFC
              6838, January 2013.

   [RFC6839]  Hansen, T. and A. Melnikov, "Additional Media Type
              Structured Syntax Suffixes", RFC 6839, January 2013.

   [XML1.1]   Bray, T., Paoli, J., Sperberg-McQueen, C.M., Maler, E.,
              Yergeau, F., and J. Cowan, "Extensible Markup Language
              (XML) 1.1 (Second Edition)", W3C Recommendation REC-xml,
              September 2006,
              <http://www.w3.org/TR/2006/REC-xml11-20060816/>.

              Latest version available at

   [XMLBase]  Marsh, J. and R. Tobin, "XML Base (Second Edition)", W3C
              Recommendation REC-xmlbase-20090128, January 2009,
              <http://www.w3.org/TR/2009/REC-xmlbase-20090128/>.

              Latest version available at

   [XML]      Bray, T., Paoli, J., Sperberg-McQueen, C.M., Maler, E.,
              and F. Yergeau, "Extensible Markup Language (XML) 1.0
              (Fifth Edition)", W3C Recommendation REC-xml, November
              2008, <http://www.w3.org/TR/2008/REC-xml-20081126/>.

              Latest version available at

   [XPointerElement]
              Grosso, P., Maler, E., Marsh, J., and N. Walsh, "XPointer
              element() Scheme", W3C Recommendation REC-XPointer-
              Element, March 2003,
              <http://www.w3.org/TR/2003/REC-xptr-element-20030325/>.

              Latest version available at

   [XPointerFramework]
              Grosso, P., Maler, E., Marsh, J., and N. Walsh, "XPointer
              Framework", W3C Recommendation REC-XPointer-Framework,



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              March 2003,
              <http://www.w3.org/TR/2003/REC-xptr-framework-20030325/>.

              Latest version available at

   [XPtrRegPolicy]
              Hazael-Massieux, D., "XPointer Scheme Name Registry
              Policy", 2005,
              <http://www.w3.org/2005/04/xpointer-policy.html>.

   [XPtrReg]  Hazael-Massieux, D., "XPointer Registry", 2005,
              <http://www.w3.org/2005/04/xpointer-schemes/>.

12.2.  Informative References

   [ASCII]    American National Standards Institute, "Coded Character
              Set -- 7-bit American Standard Code for Information
              Interchange", ANSI X3.4, 1986.

   [MediaFrags]
              Troncy, R., Mannens, E., Pfeiffer, S., and D. Van Deursen,
              "Media Fragments URI 1.0 (basic)", W3C Recommendation
              media-frags, September 2012,
              <http://www.w3.org/TR/2012/REC-media-frags-20120925/>.

              Latest version available at

   [RFC1557]  Choi, U., Chon, K., and H. Park, "Korean Character
              Encoding for Internet Messages", RFC 1557, December 1993.

   [RFC2376]  Whitehead, E. and M. Murata, "XML Media Types", RFC 2376,
              July 1998.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Nielsen, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC3023]  Murata, M., St.Laurent, S., and D. Kohn, "XML Media
              Types", RFC 3023, January 2001.

   [RFC3030]  Vaudreuil, G., "SMTP Service Extensions for Transmission
              of Large and Binary MIME Messages", RFC 3030, 2000.

   [RFC3977]  Feather, B., "Network News Transfer Protocol", RFC 3977,
              October 2006.

   [RFC5321]  Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
              October 2008.



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   [RFC6152]  Klensin, J., Freed, N., Rose, M., and D. Crocker, "SMTP
              Service Extension for 8-bit MIME Transport", RFC 6152,
              March 2011.

   [TAGMIME]  Bray, T., Ed., "Internet Media Type registration,
              consistency of use", April 2004,
              <http://www.w3.org/2001/tag/2004/0430-mime>.

   [XHTML]    Pemberton, S. and et al, "XHTML 1.0: The Extensible
              HyperText Markup Language", W3C Recommendation xhtml1,
              December 1999,
              <http://www.w3.org/TR/2000/REC-xhtml1-20000126/>.

              Latest version available at

Appendix A.  Why Use the '+xml' Suffix for XML-Based MIME Types?

   [RFC3023] contains a detailed discussion of the (at the time) novel
   use of a suffix, a practice which has since become widespread.
   Interested parties are referred to [RFC3023], Appendix A.

   The registration process for new '+xml' media types is described in
   [RFC6838]

Appendix B.  Changes from RFC 3023

   There are numerous and significant differences between this
   specification and [RFC3023], which it obsoletes.  This appendix
   summarizes the major differences only.

   First, XPointer ([XPointerFramework] and [XPointerElement]) has been
   added as fragment identifier syntax for "application/xml", and the
   XPointer Registry ([XPtrReg]) mentioned.  Second, [XMLBase] has been
   added as a mechanism for specifying base URIs.  Third, the language
   regarding character sets was updated to correspond to the W3C TAG
   finding Internet Media Type registration, consistency of use
   [TAGMIME].  Fourth, many references are updated, and the existence of
   XML 1.1 and relevance of this specification to it acknowledged.
   Finally, a number of justifications and contextualizations which were
   appropriate when XML was new have been removed, including the whole
   of the original Appendix A.

Appendix C.  Acknowledgements

   MURATA Makoto (FAMILY Given) and Alexey Melnikov made early and
   important contributions to the effort to revise [RFC3023].





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Internet-Draft              XML Media Types                November 2013


   This specification reflects the input of numerous participants to the
   ietf-xml-mime@imc.org, xml-mime@ietf.org and apps-discuss@ietf.org
   mailing lists, though any errors are the responsibility of the
   authors.  Special thanks to:

   Mark Baker, James Clark, Dan Connolly, Martin Duerst, Ned Freed,
   Yaron Goland, Bjoern Hoehrmann, Rick Jelliffe, Murray S.  Kucherawy,
   Larry Masinter, David Megginson, S.  Moonesamy, Keith Moore, Chris
   Newman, Gavin Nicol, Julian Reschke, Marshall Rose, Jim Whitehead,
   Erik Wilde and participants of the XML activity and the TAG at the
   W3C.

   Jim Whitehead and Simon St.Laurent were editors of [RFC2376] and
   [RFC3023], respectively.

Authors' Addresses

   Henry S. Thompson
   University of Edinburgh

   Email: ht@inf.ed.ac.uk
   URI:   http://www.ltg.ed.ac.uk/~ht/


   Chris Lilley
   World Wide Web Consortium
   2004, Route des Lucioles - B.P. 93 06902
   Sophia Antipolis Cedex
   France

   Email: chris@w3.org
   URI:   http://www.w3.org/People/chris/


















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