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draft-holsten-about-uri-scheme.txt
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draft-holsten-about-uri-scheme.txt
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Network Working Group J. Holsten
Internet-Draft
Intended status: Informational L. Hunt
Expires: July 5, 2009 Opera Software, ASA.
January 2009
The 'about' URI scheme
draft-holsten-about-uri-scheme-00
Status of This Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on July 5, 2009.
Copyright Notice
Copyright (c) 2009 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 in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
Abstract
This document specifies the URI (Uniform Resource Identifier) scheme
"about". About URIs are designed to be an internal, application-
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level identifier. Unlike many other URI schemes, the resolution of,
and resources represented by, about URIs are left entirely to each
individual application.
1. Editorial Note (To be removed by RFC Editor)
Discussion of this draft should take place on the URI Review mailing
list (uri-review@ietf.org).
2. Introduction
An about URI is designed to be used internally by applications for
almost any desired purpose. Such URIs have commonly been used by web
browsers for providing access to built-in functionality, such as
application information, preferences, settings, or "easter eggs".
While any number of existing schemes could be used to identify such
resources, about URIs have become the de facto standard. Browsers
already use the about scheme. The about:blank (Section 4.1) URI is
ubiquitous, and some browsers also provide other resources with the
about scheme, including those in Section 4.2.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. URI Syntax
The general syntax of a about URI, in ABNF [RFC5234] is:
abouturi = "about:" segment [ "?" query ] [ "#" fragment ]
where "segment", "query", and "fragment" are imported from [RFC3986].
In the interests of tractability to humans, about URIs SHOULD NOT be
minted with percent-encoded parts. However, the about URI syntax
does allow percent-encoded characters in the "pchar" elements defined
in [RFC3986].
No relative URI syntax is defined.
4. Resolving About URIs
In general, applications are free to resolve any about URI to any
resource, either internal or external, or redirect to an alternative
URI, with about:blank being the only exception.
As about URIs are designed to be internal to each application, there
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is no expectation of any URI, except about:blank, returning the same
resource among different applications. However, it is worth noting
that some conventions have arisen for providing particular
functionality via common about URIs.
Because about URIs identify application specific information,
applications SHOULD NOT need to retrieve remote information for such
a resource.
The about:blank URI is the only about URI reserved by this
specification.
4.1. about:blank
Applications resolving this URI MUST return an empty resource, with
the media type "text/html" and the character encoding "UTF-8".
4.2. Examples
The following examples illustrate some known URIs supported by
existing applications. They are not guaranteed to be resolvable by
every application.
about:config Commonly provides access to application preferences and
settings
about:cache Commonly provides access to information about resources
stored in the browsers cache.
about:plugins Commonly provides access to information about
installed plugins
about:mozilla An easter egg supported by Mozilla showing a passage
from the fictional Book of Mozilla
Applications are also permitted to redirect such URIs. For example,
Opera redirects all about: URIs, with the exception of about:blank,
to the equivalent URI using their internal opera: scheme. e.g. about:
config redirects to opera:config.
This is not an exhaustive list. Many more are supported by numerous
applications. For more examples, consult Wikipedia's entry on the
"about: URI Scheme" [wikiabout].
5. Security Considerations
About URIs SHOULD NOT cause the application to modify any data.
Applications SHOULD NOT use about URIs to access or erase files or
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other sensitive information.
About URIs MAY identify resources which show sensitive information.
Applications SHOULD ensure appropriate restrictions are in place to
protect such information from access or modification by untrusted
sources.
The HTML representation of the URI about:blank MUST use the origin
and the effective script origin as defined by HTML5 Section 5.4
Origin [W3C.WD-html5]. The origin of the about:blank Document is set
when the Document is created. If the new browsing context has a
creator browsing context, then the origin of the about:blank Document
is the origin of the creator Document. Otherwise, the origin of the
about:blank Document is a globally unique identifier assigned when
the new browsing context is created.
6. IANA Considerations
This specification requests the IANA permanently register the about
URI scheme as specified in this document and summarized in the
following template, per [RFC4395]:
URI scheme name: about
Status: Provisional
URI scheme syntax: See Section 3
URI scheme semantics: See Section 2
Encoding considerations: Percent-encoding is allowed in 'segment'
components (see Section 3)
Intended usage: See Section 2
Applications and/or protocols that use this URI scheme name: Any
applications that use URIs as identifiers for private resources,
such as web browsers.
Interoperability considerations: Applications are only required to
support about:blank, and may choose to interpret other about URIs
differently.
Security considerations: See Section 5
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Relevant publications: None
Contact: Joseph Holsten (joseph@josephholsten.com)
Author/Change controller: Joseph Holsten
7. Acknowledgements
This document was made possible thanks to the input of Henri Sivonen,
Ian Hickson and Larry Masinter.
8. References
8.1. Normative References
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter,
"Uniform Resource Identifier (URI): Generic Syntax",
STD 66, RFC 3986, January 2005.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
January 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[W3C.WD-html5] Hickson, I. and D. Hyatt, "HTML 5", World Wide Web
Consortium TR html5, February 2009,
<http://www.w3.org/TR/html5>.
8.2. Informative References
[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines
and Registration Procedures for New URI Schemes",
BCP 35, RFC 4395, February 2006.
[wikiabout] Wikipedia, The Free Encyclopedia, "About: URI
scheme", March 2009.
Authors' Addresses
Joseph Anthony Pasquale Holsten
EMail: joseph@josephholsten.com
URI: http://josephholsten.com
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Lachlan Hunt
Opera Software, ASA.
EMail: lachlan.hunt@lachy.id.au
URI: http://lachy.id.au/
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