发信人: kenmlee()
整理人: kenmlee(2000-01-03 11:02:00), 站内信件
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1 Introduction
#1 介绍/#
1.1 Purpose
#1.1 目的/#
The Hypertext Transfer Protocol (HTTP) is an application-level
protocol for distributed, collaborative, hypermedia information
systems. HTTP has been in use by the World-Wide Web global
information initiative since 1990. The first version of HTTP,
referred to as HTTP/0.9, was a simple protocol for raw data transfe
r
across the Internet. HTTP/1.0, as defined by RFC 1945 [6], improved
the protocol by allowing messages to be in the format of MIME-like
messages, containing metainformation about the data transferred and
modifiers on the request/response semantics. However, HTTP/1.0 does
not sufficiently take into consideration the effects of hierarchica
l
proxies, caching, the need for persistent connections, and virtual
hosts. In addition, the proliferation of incompletely-implemented
applications calling themselves "HTTP/1.0" has necessitated a
protocol version change in order for two communicating applications
to determine each other's true capabilities.
#应用级协议HTTP是用于发布、协作、超媒体信息的系统，最初于
1990年被用于WWW全球信息系统。HTTP/0.9是第一版HTTP协议,
只是一个简单的通过Internet传输原(raw)数据的协议。HTTP/1.0由
RFC1945[6]定义，增强了协议功能，允许MIME-like消息格式的消息，
包含关于传输数据本身的信息的原数据并且修改了请求和响应的语法。
然而，在分级代理、缓存、永久连接和虚拟主机的问题上HTTP/1.0并未
给与足够的考虑。并且，一些不完全实现但称其自己为“HTTP/1.0”的
应用程序在互相通讯时为确定双方的真正能力而使协议版本的改变成为
必要。/#
This specification defines the protocol referred to as "HTTP/1.1".
This protocol includes more stringent requirements than HTTP/1.0 in
order to ensure reliable implementation of its features.
#这份文档定义了“HTTP/1.1”协议，为保证其特性的可靠实现
该协议包括比HTTP/1.0更严格的要求。/#
Practical information systems require more functionality than simpl
e
retrieval, including search, front-end update, and annotation. HTTP
allows an open-ended set of methods that indicate the purpose of a
request. It builds on the discipline of reference provided by the
Uniform Resource Identifier (URI) [3][20], as a location (URL) [4]
or
name (URN) , for indicating the resource to which a method is to be
applied. Messages are passed in a format similar to that used by
Internet mail as defined by the Multipurpose Internet Mail Extensio
ns
(MIME).
#实际的信息系统要求比仅仅是简单的查询更多的功能，包括查询、
前端更新和评注（annotation）。HTTP允许通过自由应答
（open-ended）的一个方法集来指出请求的目的，它建立在URI
（Uniform Resource Identifier）的参考原则基础上，作为URL
（Location）或URN（Name）来指出方法适用的资源对象。消息
格式与Internet Mail（由MIME定义）相似。/#
HTTP is also used as a generic protocol for communication between
user agents and proxies/gateways to other Internet systems, includi
ng
those supported by the SMTP [16], NNTP [13], FTP [18], Gopher [2],
and WAIS [10] protocols. In this way, HTTP allows basic hypermedia
access to resources available from diverse applications.
#HTTP也被用于通用协议中的用户代理和代理服务器/网关（proxies/gateway
s）
间的通讯，这些Internet系统包括对SMTP，NNTP，FTP，Gopher和WAIS等
协议的支持，通过这种方式HTTP允许对不同应用资源进行基本的组合访问。
/#
1.2 Requirements
#1.2 要求/#
This specification uses the same words as RFC 1123 [8] for defining
the significance of each particular requirement. These words are:
#本文适用与RFC1123相同的单词定义每个特定要求的意义，
他们是：/#
MUST
This word or the adjective "required" means that the item is an
absolute requirement of the specification.
#MUST
这个词或其形容词“required”指出本文档中的某项特征是
要求绝对要实现的。/#
SHOULD
This word or the adjective "recommended" means that there may
exist valid reasons in particular circumstances to ignore this
item, but the full implications should be understood and the cas
e
carefully weighed before choosing a different course.
#SHOULD
这个词或其形容词“recommended”指出本文档中的某项特征
在特定的环境下有合法的原因可以忽略其实现，但应用程序必
须充分理解它的隐含意义，在选择不同的方式是因该仔细权衡。/#
MAY
This word or the adjective "optional" means that this item is
truly optional. One vendor may choose to include the item becaus
e
a particular marketplace requires it or because it enhances the
product, for example; another vendor may omit the same item.
#MAY
这个词或其形容词“recommended”指出本文档中的某项特征
是真正可选的，例如某个开发商可能因特定的市场要求或为增
强它的产品的功能选择实现这项功能，而另一个开发商可能忽
略它。/#
An implementation is not compliant if it fails to satisfy one or mo
re
of the MUST requirements for the protocols it implements. An
implementation that satisfies all the MUST and all the SHOULD
requirements for its protocols is said to be "unconditionally
compliant"; one that satisfies all the MUST requirements but not al
l
the SHOULD requirements for its protocols is said to be
"conditionally compliant."
#当一个实现不能满足一个或多个协议实现的MUST要求时，它是
不完全的。一个实现满足了所有的MUST要求和SHOULD要求
时可以被称为无条件适用的（unconditionally compliant），当它
满足所有的MUST要求但不能满足所有的SHOULD要求时被称为
条件适用的（conditionally compliant）。/#
1.3 Terminology
#1.3 术语/#
This specification uses a number of terms to refer to the roles
played by participants in, and objects of, the HTTP communication.
#本文档使用一些术语，这些术语指出HTTP通信中的各种角色和
对象。/#
connection
A transport layer virtual circuit established between two progra
ms
for the purpose of communication.
#连接connection
两个程序为通信目的而建立的传输层虚电路连接。/#
message
The basic unit of HTTP communication, consisting of a structured
sequence of octets matching the syntax defined in section 4 and
transmitted via the connection.
#消息message
基本的HTTP通信单位，由结构化的二进制序列组成，符合第4节
的语法定义，并通过连接传输。/#
request
An HTTP request message, as defined in section 5.
#请求request
HTTP请求消息，第5节定义。/#
response
An HTTP response message, as defined in section 6.
#响应response
HTTP响应消息，第6节定义。/#
resource
A network data object or service that can be identified by a URI
,
as defined in section 3.2. Resources may be available in multipl
e
representations (e.g. multiple languages, data formats, size,
resolutions) or vary in other ways.
#资源resource
由URI标示网络数据对象或服务，第3.2节定义。资源可以被
多种方式所表现（如，多种语言，数据格式，大小，解析度等）
或在其它方面不同。/#
entity
The information transferred as the payload of a request or
response. An entity consists of metainformation in the form of
entity-header fields and content in the form of an entity-body,
as
described in section 7.
#实体entity
作为请求或响应的净荷传输的信息。一个实体由包含元信息的
实体头和实体体组成，见第7节描述。/#
representation
An entity included with a response that is subject to content
negotiation, as described in section 12. There may exist multipl
e
representations associated with a particular response status.
#表现representation
实体包括与内容协商相一致的响应，见第12节的描述。特定
的响应状态可能会与多个表现相关。/#
content negotiation
The mechanism for selecting the appropriate representation when
servicing a request, as described in section 12. The
representation of entities in any response can be negotiated
(including error responses).
#内容协商content negotiation
当为某个请求服务时选择合适的表现的机制，见第12节的描述。
任何响应中的实体表现都可以协商（包括错误响应）。/#
variant
A resource may have one, or more than one, representation(s)
associated with it at any given instant. Each of these
representations is termed a `variant.' Use of the term `variant'
does not necessarily imply that the resource is subject to conte
nt
negotiation.
#变量variant
资源可能有一个或多个与给定实例相关的表现，每个表现都
称为“变量”，使用“变量”一词并不意味着资源必须与内
容协商相一致。/#
client
A program that establishes connections for the purpose of sendin
g
requests.
#客户client
为发送请求的目的而建立连接的程序。/#
user agent
The client which initiates a request. These are often browsers,
editors, spiders (web-traversing robots), or other end user tool
s.
#用户代理user agent
初始化请求的客户，一般来说是指浏览器，编辑器，spiders
（web搜索机器人robots）或其它用户端工具。/#
server
An application program that accepts connections in order to
service requests by sending back responses. Any given program ma
y
be capable of being both a client and a server; our use of these
terms refers only to the role being performed by the program for
a
particular connection, rather than to the program's capabilities
in general. Likewise, any server may act as an origin server,
proxy, gateway, or tunnel, switching behavior based on the natur
e
of each request.
#服务器server
通过发送回响应来为请求提供服务的接受连接的应用程序。任何
程序都有能力即作为客户又作为服务器，我们只是使用这些术语
表示程序在特定的连接中所扮演的角色，而不是一般所言的程序
的功能。类似的，任何服务器可以作为一个原始服务器，代理，
网关或隧道，根据每个请求的特性改变其行为。/#
origin server
The server on which a given resource resides or is to be created
.
#原始服务器origin server
给定资源驻留或被创建的服务器。/#
proxy
An intermediary program which acts as both a server and a client
for the purpose of making requests on behalf of other clients.
Requests are serviced internally or by passing them on, with
possible translation, to other servers. A proxy must implement
both the client and server requirements of this specification.
#代理proxy
为其它客户的请求服务，即作服务器又作客户的中间程序。
请求被代理先处理或通过代理，可能经过一定的转换，转发
到服务器上。代理必须同时实现本文档的客户和服务器实现
要求。/#
gateway
A server which acts as an intermediary for some other server.
Unlike a proxy, a gateway receives requests as if it were the
origin server for the requested resource; the requesting client
may not be aware that it is communicating with a gateway.
#网关gateway
扮演其它服务器中间程序角色的服务器。与代理不同，网关
接受请求就好像它是请求资源的原始服务器一样，请求客户
并不知道他是在和网关通信。/#
tunnel
An intermediary program which is acting as a blind relay between
two connections. Once active, a tunnel is not considered a party
to the HTTP communication, though the tunnel may have been
initiated by an HTTP request. The tunnel ceases to exist when bo
th
ends of the relayed connections are closed.
#隧道tunnel
在两个连接间扮演盲中继的中间程序。虽然隧道可能是被HTTP
请求发起的，但在激活后，隧道并不是HTTP通信的一部分。/#
cache
A program's local store of response messages and the subsystem
that controls its message storage, retrieval, and deletion. A
cache stores cachable responses in order to reduce the response
time and network bandwidth consumption on future, equivalent
requests. Any client or server may include a cache, though a cac
he
cannot be used by a server that is acting as a tunnel.
#缓存cache
程序对响应信息的局部存储和控制信息储存，获取，删除等
操作的子系统。缓存保存可缓存的响应信息以便减少对相同
的请求的响应时间和将来的网络带宽消耗，任何客户和服务
器都可以包含缓存，然而当服务器作为隧道使用时不能使用
缓存。/#
cachable
A response is cachable if a cache is allowed to store a copy of
the response message for use in answering subsequent requests. T
he
rules for determining the cachability of HTTP responses are
defined in section 13. Even if a resource is cachable, there may
be additional constraints on whether a cache can use the cached
copy for a particular request.
#可缓存cachable
如果缓存机制允许保存响应信息的拷贝以便用于其后的请求，
则此响应是可缓存的。第13节定义了HTTP响应的可缓存能力
的决定规则。即使资源是可缓存的，是否缓存机制可以使用
特定请求的缓存拷贝也有其它限制条件。/#
first-hand
A response is first-hand if it comes directly and without
unnecessary delay from the origin server, perhaps via one or mor
e
proxies. A response is also first-hand if its validity has just
been checked directly with the origin server.
#第一手(直接)first-hand
从原始服务器产生的中间没有经过一个或多个代理不必要的
延迟的响应称为第一手(直接)的,如果响应的有效性得到原始
服务器的直接检查也可以认为是第一手的./#
explicit expiration time
The time at which the origin server intends that an entity shoul
d
no longer be returned by a cache without further validation.
#显式超时时间explicit expiration time
原始服务器指定如果没有更进一步的验证,实体不应再由缓存返回./#
heuristic expiration time
An expiration time assigned by a cache when no explicit expirati
on
time is available.
#混合超时时间heuristic expiration time
没有显式超时时间时缓存所赋予的超时时间./#
age
The age of a response is the time since it was sent by, or
successfully validated with, the origin server.
#年龄age
响应的年龄是指它被原始服务器发送或成功验证以来的时间./#
freshness lifetime
The length of time between the generation of a response and its
expiration time.
#有效生命期freshness lifttime
响应从生成到超时所经过的时间长度./#
fresh
A response is fresh if its age has not yet exceeded its freshnes
s
lifetime.
#有效fresh
如果一个响应的年龄没有超过它的有效生命期则它是有效的./#
stale
A response is stale if its age has passed its freshness lifetime
.
#失效stale
如果一个响应的年龄超过了它的有效生命期则它是失效的./#
semantically transparent
A cache behaves in a "semantically transparent" manner, with
respect to a particular response, when its use affects neither t
he
requesting client nor the origin server, except to improve
performance. When a cache is semantically transparent, the clien
t
receives exactly the same response (except for hop-by-hop header
s)
that it would have received had its request been handled directl
y
by the origin server.
#语法透明
对特定的响应,语法透明缓存表现出这样的行为,除提高性能外,
即不影响请求客户又不影响原始服务器.当缓存是语法透明的时,
客户接收到的响应和它直接向原始服务器请求所返回的响应时一
样的(除了每跳的头部)./#
validator
A protocol element (e.g., an entity tag or a Last-Modified time)
that is used to find out whether a cache entry is an equivalent
copy of an entity.
#验证子
一个协议元素(例如,一个实体标签或一个最后修改时间)用于找出
一个缓存条目是否与一个实体的拷贝相等./#
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