内容折衝応答

仕様書から

RFC 2295 (HTTP 透過内容折衝) 10 Content negotiation responses

If a request on a transparently negotiated resource yields a response with a 2xx status code or any 3xx status code except 304, this response MUST always be either a list response, a choice response, or an adhoc response. These responses MUST always include a TCN header which specifies their type. Transparently negotiated responses with other status codes MAY also include a TCN header.

透過内容折衝資源の要求が 2xx 状態符号又は 304 を除く 3xx 状態符号の応答を得る場合、この応答は常に目録応答か選択応答か臨時応答のいずれかでなければなりません。これらの応答は常にその型を指定した TCN 頭を含まなければなりません。他の状態符号の透過折衝資源も TCN 頭を含んでも構いません。

The conditions under which the different content negotiation responses may be sent are defined in section 12.1 for origin servers and in section 13 for proxies.

After having constructed a list, choice, or adhoc response, a server MAY process any If-No-Match or If-Range headers in the request message and shorten the response to a 304 (Not Modified) or 206 (Partial Content) response, following the rules in the HTTP/1.1 specification [1]. In this case, the entity tag of the shortened response will identify it indirectly as a list, choice, or adhoc response.

目録応答, 選択応答または臨時応答を構築した後に、サーバーは要求メッセージの If-No-Match 頭又は If-Range 頭を HTTP/1.1 仕様書に従って処理してこの応答を 304 (未修正) 応答又は 306 (部分内容) 応答に短しめても構いません。この場合、短しめた応答の実体札は間接的に目録応答, 選択応答または臨時応答を識別することとなります。