In a response to a HEAD request, the representation header fields describe the representation data that would have been enclosed in the payload body if the same request had been a GET.
in the Content-Type (Section 220.127.116.11) and Accept (Section 5.3.2) header fields in order to provide open and extensible data typing and type negotiation.
MIME's canonical form requires that media subtypes of the "text" type use CRLF as the text line break.
HTTP allows the transfer of text media with plain CR or LF alone representing a line break, when such line breaks are consistent for an entire representation.
The presence or absence of a parameter might be significant to the processing of a media-type, depending on its definition within the media type registry.Considering that a resource could be anything, and that the uniform interface provided by HTTP is similar to a window through which one can observe and act upon such a thing only through the communication of messages to some independent actor on the other side, an abstraction is needed to represent ("take the place of") the current or desired state of that thing in our communications.That abstraction is called a representation " is information that is intended to reflect a past, current, or desired state of a given resource, in a format that can be readily communicated via the protocol, and that consists of a set of representation metadata and a potentially unbounded stream of representation data.A client constructs request messages to communicate specific intentions, examines received responses to see if the intentions were carried out, and determines how to interpret the results.This document defines HTTP/1.1 request and response semantics in terms of the architecture defined in HTTP semantics include the intentions defined by each request method (Section 4), extensions to those semantics that might be described in request header fields (Section 5), the meaning of status codes to indicate a machine-readable response (Section 6), and the meaning of other control data and resource metadata that might be given in response header fields (Section 7).Appendix D shows the collected grammar with all list operators expanded to standard ABNF notation.".HTTP does not limit the nature of a resource; it merely defines an interface that might be used to interact with resources.The Hypertext Transfer Protocol (HTTP) is a stateless application-level protocol for distributed, collaborative, hypertext information systems.This document defines the semantics of HTTP/1.1 messages, as expressed by request methods, request header fields, response status codes, and response header fields, along with the payload of messages (metadata and body content) and mechanisms for content negotiation.Each resource is identified by a Uniform Resource Identifier (URI), as described in Section 2.7 of One design goal of HTTP is to separate resource identification from request semantics, which is made possible by vesting the request semantics in the request method (Section 4) and a few request-modifying header fields (Section 5).If there is a conflict between the method semantics and any semantic implied by the URI itself, as described in Section 4.2.1, the method semantics take precedence.