Network Working Group J. Holsten Internet-Draft Intended status: Informational L. Hunt Expires: February 13, 2010 Opera Software, ASA. August 12, 2009 The 'about' URI scheme draft-holsten-about-uri-scheme-02 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 February 13, 2010. 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- Holsten & Hunt Expires February 13, 2010 [Page 1] Internet-Draft The 'about' URI scheme August 2009 level identifier. Unlike many other URI schemes, the resolution of, and resources represented by, about URIs are left largely to each individual application. Only the "about:blank" URI must be the same. 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 5.1) URI is ubiquitous, and some browsers also provide other resources with the about scheme, including those in Section 5.2. 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 an about URI is defined below using ABNF [RFC5234]: abouturi = "about:" segment [ "?" query ] where "segment" and "query" are defined in [RFC3986]. 4. Encoding Considerations Because many characters are not permitted with this syntax, the "segment" and "query" elements may contain characters from the Unicode Character Set [UCS] as suggested by URI [RFC3986], by first encoding those characters as octets to the UTF-8 character encoding [RFC3629]; then only those octets that do not correspond to characters in the unreserved set should be percent-encoded. By using UTF-8 encoding, there are no known compatibility issues with mapping Internationlized Resource Identifiers to about URIs according to [RFC3987]. Since about URIs do not use domain names, "ireg-name" conversion is unnecessary. Holsten & Hunt Expires February 13, 2010 [Page 2] Internet-Draft The 'about' URI scheme August 2009 5. 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. Because about URIs identify application specific information, applications SHOULD NOT retrieve remote information for such a resource. The about:blank URI is the only about URI reserved by this specification. 5.1. about:blank Applications resolving this URI MUST return an empty resource, with the media type "text/html" and the character encoding "UTF-8". 5.2. 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 Holsten & Hunt Expires February 13, 2010 [Page 3] Internet-Draft The 'about' URI scheme August 2009 applications. For more examples, consult Wikipedia's entry on the "about: URI Scheme" [wikiabout]. 6. Normalization About URIs use the standard URI normalization rules [RFC3986], specifically Simple String Comparison, Case Normalization, and Percent-Encoding Normalization. For example, "about:blank", "about:blan%6B" and "about:blan%6b" are equivalent, though the percent-encoded forms are discouraged. Due to the structure of about URIs, some normalizations do not apply, specifically Syntax-Based Normalization, Scheme-Based Normalization, and Protocol-Based Normalization. For example, "about:blank" is not equivalent to "about:BLANK", "about:blank?" or "about:blank:", each may represent a different resource. Similarly, "about:blank%3F" is not equivalent to "about:blank?". 7. Relative About URIs As about URIs do not use a hierarchical path, relative about URIs are not permitted 8. Security Considerations Implementations of the scheme SHOULD NOT modify data when processing about resource identifiers. Applications SHOULD NOT use about URIs to access or erase files or 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. 9. IANA Considerations This specification requests the IANA provisionally register the about URI scheme as specified in this document and summarized in the following template, per [RFC4395]: Holsten & Hunt Expires February 13, 2010 [Page 4] Internet-Draft The 'about' URI scheme August 2009 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" and "query" components. Internationalization is handled by IRI processing. See Section 4. 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 8 Relevant publications: None Contact: Joseph Holsten (joseph@josephholsten.com) Author/Change controller: Joseph Holsten 10. Acknowledgements This document was made possible thanks to the input of Henri Sivonen, Ian Hickson and Larry Masinter. 11. References 11.1. 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 Holsten & Hunt Expires February 13, 2010 [Page 5] Internet-Draft The 'about' URI scheme August 2009 Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, January 2005. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003. [UCS] International Organization for Standardization, "Information Technology - Universal Multiple-Octet Coded Character Set (UCS)", ISO/IEC Standard 10646, December 2003. [W3C.WD-html5] Hickson, I. and D. Hyatt, "HTML 5", World Wide Web Consortium TR html5, February 2009, . 11.2. 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 Lachlan Hunt Opera Software, ASA. EMail: lachlan.hunt@lachy.id.au URI: http://lachy.id.au/ Holsten & Hunt Expires February 13, 2010 [Page 6]