Network Working Group J. Holsten
Internet-Draft N/A
Intended status: Informational L. Hunt
Expires: July 31, 2009 Opera Software, ASA.
January 27, 2009
The 'about' URI scheme
draft-holsten-about-uri-scheme-00
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Abstract
This document specifies the URI (Uniform Resource Identifier) scheme
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"about". About URIs are designed to be an internal, application-
level identifier. Unlike many other URI schemes, the resolution of,
and resources represented by, about URIs are left entirely to each
individual application.
1. 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 proving access to built-in functionality, such as
application preferences and settings, information about the
application, or "easter eggs".
About URIs are more memorable than an equivalent urn or tag URI.
Using an http URI would not only be less memorable, but also longer
and semantically confusing. 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 3.1) URI is ubiquitous, and some browsers also
provide other resources with the about scheme, including those in
Section 3.2.
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].
2. URI Syntax
The general syntax of a about URI, in ABNF [RFC5234] is:
abouturi = "about:" segment
where "segment" is imported from [RFC3986]. About URIs are always
escaped, as per [RFC3986].
No relative URI syntax is defined.
3. 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
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.
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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.
3.1. about:blank
This URI identifies an empty resource. If the application may use a
document of MIME type 'text/html' and character encoding 'UTF-8',
about:blank SHOULD be represented with an empty document. Other
representations are not defined.
3.2. 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
about:internets An easter egg supported by Google Chrome depicting
the internet as a series of tubes.
4. Acknowledgements
This document was made possible thanks to the input of Henri Sivonen,
Ian Hickson and Larry Masinter.
5. Security Considerations
There is no guarantee that an application will understand any about
URI provided to it. An about URI may not resolve to the expected
resource. If the reference is unlikely to resolve correctly, the
reference should be accompanied by an explanation or alternatives.
Some applications are known to display arbitrary HTML following the
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scheme. Applications should be cautious when accessing an about URI.
An application should not execute or display information in an about
URI. About URIs should not cause the application to modify any data.
Applications should not use about URIs to access, or erase files or
other sensitive information.
About URIs may identify resources which show sensitive information.
This data SHOULD NOT be exposed in about URIs.>
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 2
URI scheme semantics: See Section 1
Encoding considerations: Percent-encoding is allowed in 'segment'
components (see Section 2)
Intended usage: See Section 1
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. Other about URIs should only be expected to work
correctly within the same application.
Security considerations: See Section 5
Relevant publications: None
Contact: Joseph Holsten (joseph@josephholsten.com)
Author/Change controller: Joseph Holsten
7. References
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7.1. 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.
7.2. Informative References
[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
Registration Procedures for New URI Schemes", BCP 115,
RFC 4395, February 2006.
Authors' Addresses
Joseph Anthony Pasquale Holsten
N/A
EMail: joseph@josephholsten.com
URI: http://josephholsten.com
Lachlan Hunt
Opera Software, ASA.
EMail: lachlan.hunt@lachy.id.au
URI: http://lachy.id.au/
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