content negotiation

HTTP defines proactive content negotiation to allow servers to select the appropriate response for a given request, based upon the user agent's characteristics, as expressed in request headers. In practice, user agents are often unwilling to send those request headers, because it is not clear whether they will be used, and sending them impacts both performance and privacy.

This document defines an Accept-CH response header that servers can use to advertise their use of request headers for proactive content negotiation, along with a set of guidelines for the creation of such headers, colloquially known as "Client Hints."

The HTTP-based Memento framework bridges the present and past Web. It facilitates obtaining representations of prior states of a given resource by introducing datetime negotiation and TimeMaps. Datetime negotiation is a variation on content negotiation that leverages the given resource's URI and a user agent's preferred datetime. TimeMaps are lists that enumerate URIs of resources that encapsulate prior states of the given resource. The framework also facilitates recognizing a resource that encapsulates a frozen prior state of another resource.

This document defines and registers with IANA the new "fax" media feature tag for use with the Session Initiation Protocol (SIP). Currently, fax calls are indistinguishable from voice calls at call initiation. Consequently, fax calls can be routed to SIP user agents that are not fax capable. A "fax" media feature tag implemented in conjunction with caller preferences allows for more accurate fax call routing.

The caller preferences specification for the Session Initiation Protocol (SIP) allows a caller to express preferences that the call be routed to a User Agent (UA) with particular capabilities. Similarly, a specification exists to allow a UA to indicate its capabilities in a registration. Amongst those capabilities are the type of media streams the agent supports, described as top-level MIME types. The 'application' MIME type is used to describe a broad range of stream types, and it provides insufficient granularity as a capability. This specification allows a UA to indicate which application subtypes the agent supports. [STANDARDS-TRACK]

This document registers with the IANA a new media feature tag associated with the 'message' media type. This media feature tag indicates that a particular device supports 'message' as a streaming media type. Media feature tags can be used to route calls to devices that support certain features. This memo provides information for the Internet community.

This memo describes a content negotiation mechanism for facsimile, voice and other messaging services that use Internet email. [STANDARDS-TRACK]

This document contains the registration for two media feature tags: "charset" and "language". [STANDARDS-TRACK]

This memo defines a Multipurpose Internet Mail Extensions (MIME) ' Content-features:' header that can be used to annotate a MIME message part using this expression format, and indicates some ways it might be used. [STANDARDS-TRACK]

This memo defines a media feature tag whose value is a Multipurpose Internet Mail Extensions (MIME) content type. [STANDARDS-TRACK]

This document describes an abbreviated format for a composite media feature set, based upon a hash of the feature expression describing that composite. [STANDARDS-TRACK]

In RFC 2533, "A Syntax for Describing Media Feature Sets", an expression format is presented for describing media feature capabilities using simple media feature tags. This memo contains two corrections to that specification: one fixes an error in the formal syntax specification, and the other fixes an error in the rules for reducing feature comparison predicates. [STANDARDS-TRACK]

This memo sets out terminology, an abstract framework and goals for protocol-independent content negotiation, and identifies some technical issues which may need to be addressed. This memo provides information for the Internet community.

This document defines a registration procedure which uses the Internet Assigned Numbers Authority (IANA) as a central registry for the media feature vocabulary. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.

This memo describes a format for generating Message Disposition Notifications and Delivery Status Notifications which contain such information. [STANDARDS-TRACK]

This document introduces and describes a syntax that can be used to define feature sets which are formed from combinations and relations involving individual media features. [STANDARDS-TRACK]

This specification defines some common media features for describing image resolution, size, color, and image representation methods that are common to web browsing, printing, and facsimile applications. [STANDARDS-TRACK]

HTTP allows web site authors to put multiple versions of the same information under a single URL. Transparent content negotiation is an extensible negotiation mechanism, layered on top of HTTP, for automatically selecting the best version when the URL is accessed. This enables the smooth deployment of new web data formats and markup tags. This memo defines an Experimental Protocol for the Internet community. It does not specify an Internet standard of any kind. Discussion and suggestions for improvement are requested.