[1] [[HTTP]] の[[要求]]や[[応答]]はそもそも1組ずつそれぞれ独立したものですが、
複数の[[要求]]と[[応答]]の組の間にわたって[RUBYB[[[状態]]]@en[state]]を持たせたいことがあります。
その[[要求]]と[[応答]]の集合によって構成される[RUBYB[文脈]@en[context]]を[DFN[[RUBYB[セッション]@en[session]]]]といいます。

* 仕様書

- [2] [DEL[[[RFC 2109]]]] ([[廃止]]済み)
-- [CSECTION@en[3. STATE AND SESSIONS]]
- [3] [[RFC 2965]]
-- [CSECTION@en[2. STATE AND SESSIONS]]

* 仕様書から

[4] 
>
This document describes a way to create stateful sessions with HTTP
requests and responses.  Currently, HTTP servers respond to each
client request without relating that request to previous or
subsequent requests; [DEL[the technique]] [INS[the state management mechanism]]
allows clients and servers that wish to exchange state information to place HTTP
requests and responses within a larger context, which we term a
"session".  This context might be used to create, for example, a
"shopping cart", in which user selections can be aggregated before
purchase, or a magazine browsing system, in which a user's previous
reading affects which offerings are presented.

[DEL(rfc2965)[
>   There are, of course, many different potential contexts and thus many
different potential types of session.  The designers' paradigm for
sessions created by the exchange of cookies has these key attributes:
=  Each session has a beginning and an end.
=  Each session is relatively short-lived.
=  Either the user agent or the origin server may terminate a session.
=  The session is implicit in the exchange of state information.
]DEL]

[INS(rfc2965)[
>   Neither clients nor servers are required to support cookies.  A
server MAY refuse to provide content to a client that does not return
the cookies it sends.
]DEL]

** License

[5] [[RFCのライセンス]]