Changeset 1770 for draft-ietf-httpbis/latest/p6-cache.html
- Timestamp:
- 14/07/12 12:41:41 (10 years ago)
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draft-ietf-httpbis/latest/p6-cache.html
r1769 r1770 787 787 in this document are to be interpreted as described in <a href="#RFC2119" id="rfc.xref.RFC2119.1"><cite title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</cite></a>. 788 788 </p> 789 <p id="rfc.section.1.3.p.2">This document defines conformance criteria for several roles in HTTP communication, including Senders, Recipients, Clients, 790 Servers, User-Agents, Origin Servers, Intermediaries, Proxies and Gateways. See <a href="p1-messaging.html#architecture" title="Architecture">Section 2</a> of <a href="#Part1" id="rfc.xref.Part1.1"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for definitions of these terms. 791 </p> 792 <p id="rfc.section.1.3.p.3">An implementation is considered conformant if it complies with all of the requirements associated with its role(s). Note that 793 SHOULD-level requirements are relevant here, unless one of the documented exceptions is applicable. 794 </p> 795 <p id="rfc.section.1.3.p.4">This document also uses ABNF to define valid protocol elements (<a href="#notation" title="Syntax Notation">Section 1.4</a>). In addition to the prose requirements placed upon them, Senders <em class="bcp14">MUST NOT</em> generate protocol elements that are invalid. 796 </p> 797 <p id="rfc.section.1.3.p.5">Unless noted otherwise, Recipients <em class="bcp14">MUST</em> be able to parse all protocol elements matching the ABNF rules defined for them and <em class="bcp14">MAY</em> take steps to recover a usable protocol element from an invalid construct. However, HTTP does not define specific error handling 798 mechanisms, except in cases where it has direct impact on security. This is because different uses of the protocol require 799 different error handling strategies; for example, a Web browser might wish to transparently recover from a response where 800 the <a href="p2-semantics.html#header.location" class="smpl">Location</a> header field doesn't parse according to the ABNF, whereby in a systems control protocol using HTTP, this type of error recovery 801 could lead to dangerous consequences. 789 <p id="rfc.section.1.3.p.2">This specification targets conformance criteria according to the role of a participant in HTTP communication. Hence, HTTP 790 requirements are placed on senders, recipients, clients, servers, user agents, intermediaries, origin servers, proxies, gateways, 791 or caches, depending on what behavior is being constrained by the requirement. See <a href="p1-messaging.html#architecture" title="Architecture">Section 2</a> of <a href="#Part1" id="rfc.xref.Part1.1"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for definitions of these terms. 792 </p> 793 <p id="rfc.section.1.3.p.3">The verb "generate" is used instead of "send" where a requirement differentiates between creating a protocol element and merely 794 forwarding a received element downstream. 795 </p> 796 <p id="rfc.section.1.3.p.4">An implementation is considered conformant if it complies with all of the requirements associated with the roles it partakes 797 in HTTP. Note that SHOULD-level requirements are relevant here, unless one of the documented exceptions is applicable. 798 </p> 799 <p id="rfc.section.1.3.p.5">This document also uses ABNF to define valid protocol elements (<a href="#notation" title="Syntax Notation">Section 1.4</a>). In addition to the prose requirements placed upon them, senders <em class="bcp14">MUST NOT</em> generate protocol elements that do not match the grammar defined by the ABNF rules for those protocol elements that are applicable 800 to the sender's role. If a received protocol element is processed, the recipient <em class="bcp14">MUST</em> be able to parse any value that would match the ABNF rules for that protocol element, excluding only those rules not applicable 801 to the recipient's role. 802 </p> 803 <p id="rfc.section.1.3.p.6">Unless noted otherwise, a recipient <em class="bcp14">MAY</em> attempt to recover a usable protocol element from an invalid construct. HTTP does not define specific error handling mechanisms 804 except when they have a direct impact on security, since different applications of the protocol require different error handling 805 strategies. For example, a Web browser might wish to transparently recover from a response where the <a href="p2-semantics.html#header.location" class="smpl">Location</a> header field doesn't parse according to the ABNF, whereas a systems control client might consider any form of error recovery 806 to be dangerous. 802 807 </p> 803 808 <h2 id="rfc.section.1.4"><a href="#rfc.section.1.4">1.4</a> <a id="notation" href="#notation">Syntax Notation</a></h2>
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