draft-ietf-appsawg-xml-mediatypes-06.txt   draft-ietf-appsawg-xml-mediatypes-07.txt 
Network Working Group H. S. Thompson Network Working Group H. S. Thompson
Internet-Draft University of Edinburgh Internet-Draft University of Edinburgh
Obsoletes: 3023 (if approved) C. Lilley Obsoletes: 3023 (if approved) C. Lilley
Updates: 6839 (if approved) W3C Updates: 6839 (if approved) W3C
Intended status: Standards Track December 05, 2013 Intended status: Standards Track February 06, 2014
Expires: June 08, 2014 Expires: August 10, 2014
XML Media Types XML Media Types
draft-ietf-appsawg-xml-mediatypes-06 draft-ietf-appsawg-xml-mediatypes-07
Abstract Abstract
This specification standardizes three media types -- application/xml, This specification standardizes three media types -- application/xml,
application/xml-external-parsed-entity, and application/xml-dtd -- application/xml-external-parsed-entity, and application/xml-dtd --
for use in exchanging network entities that are related to the for use in exchanging network entities that are related to the
Extensible Markup Language (XML) while defining text/xml and text/ Extensible Markup Language (XML) while defining text/xml and text/
xml-external-parsed-entity as aliases for the respective application/ xml-external-parsed-entity as aliases for the respective application/
types. This specification also standardizes the '+xml' suffix for types. This specification also standardizes the '+xml' suffix for
naming media types outside of these five types when those media types naming media types outside of these five types when those media types
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 08, 2014. This Internet-Draft will expire on August 10, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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The registrations below all address issues around character encoding The registrations below all address issues around character encoding
in the same way, by referencing this section. in the same way, by referencing this section.
As many as three distinct sources of information about character As many as three distinct sources of information about character
encoding may be present for an XML MIME entity: a charset parameter, encoding may be present for an XML MIME entity: a charset parameter,
a Byte Order Mark (BOM -- see Section 3.3 below) and an XML encoding a Byte Order Mark (BOM -- see Section 3.3 below) and an XML encoding
declaration (see Section 4.3.3 of [XML]). Ensuring consistency among declaration (see Section 4.3.3 of [XML]). Ensuring consistency among
these sources requires coordination between entity authors and MIME these sources requires coordination between entity authors and MIME
agents (that is, processes which package, transfer, deliver and/or agents (that is, processes which package, transfer, deliver and/or
receive MIME entities). Some MIME agents will be what we will call receive MIME entities).
"XML-aware", that is, capable of processing XML MIME entities and
detecting the XML encoding declaration (or its absence). Others will The use of UTF-8, without a BOM, is RECOMMENDED for all XML MIME
not be XML-aware, and thus cannot know anything about the XML entities.
encoding declaration. Some MIME agents, such as proxies and
transcoders, both consume and produce MIME entities. Some MIME agents will be what we will call "XML-aware", that is,
capable of processing XML MIME entities as XML and detecting the XML
encoding declaration (or its absence). Others, while comforming to
this and other media type registrations, 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.
3.1. XML MIME producers 3.1. XML MIME producers
XML-aware MIME producers SHOULD supply a charset parameter and/or an XML-aware MIME producers SHOULD supply a charset parameter and/or an
appropriate BOM with non-UTF-8-encoded XML MIME entities which lack appropriate BOM with non-UTF-8-encoded XML MIME entities which lack
an encoding declaration, and SHOULD remove or correct an encoding an encoding declaration, and SHOULD remove or correct an encoding
declaration which is known to be incorrect (for example, as a result declaration which is known to be incorrect (for example, as a result
of transcoding). of transcoding).
XML-aware MIME producers MUST supply an XML text declaration at the XML-aware MIME producers MUST supply an XML text declaration at the
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it is present in an XML MIME entity. In the absence of a BOM it is present in an XML MIME entity. In the absence of a BOM
(Section 3.3), all consumers SHOULD treat the charset parameter as (Section 3.3), all consumers SHOULD treat the charset parameter as
authoritative if it is present. For XML-aware consumers, note authoritative if it is present. For XML-aware consumers, note
that Section 4.3.3 of [XML] does _not_ make it an error for the that Section 4.3.3 of [XML] does _not_ make it an error for the
charset parameter and the XML encoding declaration (or the UTF-8 charset parameter and the XML encoding declaration (or the UTF-8
default in the absence of encoding declaration and BOM) to be default in the absence of encoding declaration and BOM) to be
inconsistent, although such consumers might choose to issue a inconsistent, although such consumers might choose to issue a
warning in this case. warning in this case.
When MIME producers conform to the requirements stated above When MIME producers conform to the requirements stated above
(Section 3.1), such inconsistencies will not arise---this statement (Section 3.1, Section 3) such inconsistencies will not arise---this
of priorities only has practical impact in the case of non-conforming statement of priorities only has practical impact in the case of non-
XML MIME entities. conforming XML MIME entities.
If an XML MIME entity is received where the charset parameter is If an XML MIME entity is received where the charset parameter is
omitted, no information is being provided about the character omitted, no information is being provided about the character
encoding by the MIME Content-Type header. XML-aware consumers MUST encoding by the MIME Content-Type header. XML-aware consumers MUST
follow the requirements in section 4.3.3 of [XML] that directly follow the requirements in section 4.3.3 of [XML] that directly
address this case. XML-unaware MIME consumers SHOULD NOT assume a address this case. XML-unaware MIME consumers SHOULD NOT assume a
default encoding in this case. default encoding in this case.
3.3. The Byte Order Mark (BOM) and Encoding Conversions 3.3. The Byte Order Mark (BOM) and Encoding Conversions
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An XML document labeled as application/xml or text/xml, or with a An XML document labeled as application/xml or text/xml, or with a
'+xml' media type, might contain namespace declarations, stylesheet- '+xml' media type, might contain namespace declarations, stylesheet-
linking processing instructions (PIs), schema information, or other linking processing instructions (PIs), schema information, or other
declarations that might be used to suggest how the document is to be declarations that might be used to suggest how the document is to be
processed. For example, a document might have the XHTML namespace processed. For example, a document might have the XHTML namespace
and a reference to a CSS stylesheet. Such a document might be and a reference to a CSS stylesheet. Such a document might be
handled by applications that would use this information to dispatch handled by applications that would use this information to dispatch
the document for appropriate processing. Appendix B lists the core the document for appropriate processing. Appendix B lists the core
XML specifications which, taken together with [XML] itself, show how XML specifications which, taken together with [XML] itself, show how
to determine an XML document's semantics at both the language level to determine an XML document's language-level semantics and suggest
and the application level. how information about its application-level semantics may be
locatable.
4.2. Application/xml Registration 4.2. Application/xml Registration
Type name: application Type name: application
Subtype name: xml Subtype name: xml
Required parameters: none Required parameters: none
Optional parameters: charset Optional parameters: charset
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