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 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 31, 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. 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 Holsten & Hunt Expires July 31, 2009 [Page 1] Internet-Draft The 'about' URI scheme January 2009 "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. Holsten & Hunt Expires July 31, 2009 [Page 2] Internet-Draft The 'about' URI scheme January 2009 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 Holsten & Hunt Expires July 31, 2009 [Page 3] Internet-Draft The 'about' URI scheme January 2009 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 Holsten & Hunt Expires July 31, 2009 [Page 4] Internet-Draft The 'about' URI scheme January 2009 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/ Holsten & Hunt Expires July 31, 2009 [Page 5]