[19] [DFN[[[SDCH]]]] は、外部辞書を使った [[HTTP]] の[[圧縮]]方式です。
[[Google]] の[[鯖]]と [[Chrome]] が実装しています。

* 仕様書

[REFS[
- [14] [CITE[Shared Dictionary Compression over HTTP - Google ドキュメント]] ([TIME[2014-11-19 23:46:56 +09:00]] 版) <https://docs.google.com/a/chromium.org/document/d/1REMkwjXY5yFOkJwtJPjCMwZ4Shx3D9vfdAytV_KQCUo/edit?pli=1>
]REFS]

* プロトコル

[15] [[内容符号化]]の名前 [DFN[[CODE(HTTP)@en[[[sdch]]]]]] を規定しています [SRC[>>14]]。

;; [16] [[転送符号化]]の方が意味的には正しそうですが、現在の利用状況を鑑み[[内容符号化]]に敢えてしているようです [SRC[>>12]]。

[17] 次の[[ヘッダー]]を規定しています。
[FIG(short list)[
- [CODE(HTTP)@en[[[Get-Dictionary:]]]]
- [CODE(HTTP)@en[[[Avail-Dictionary:]]]]
- [CODE(HTTP)@en[[[X-SDCH-Encode:]]]]
]FIG]

[18] [[MIME型]] [DFN[[CODE(MIME)@en[[[application/x-sdch-dictionary]]]]]]
を定義しています [SRC[>>14]]。

* 歴史

[1]
[CITE@en[A proposal for Shared Dictionary Compression over HTTP]] ([[Wei-Hsin Lee]] 著, [CODE[2008-09-09 05:59:47 +09:00]] 版) <http://lists.w3.org/Archives/Public/ietf-http-wg/2008JulSep/0441.html>
([[名無しさん]])


[2]
[CITE[SDCH | Google グループ]] ([TIME[2008-09-09 17:16:53 +09:00]] 版) <http://groups.google.com/group/SDCH>

[3] [CITE[mod-sdch - Project Hosting on Google Code]]
( ([TIME[2011-02-05 20:46:09 +09:00]] 版))
<http://code.google.com/p/mod-sdch/>

[4] [[Chrome]] は [CODE(HTTP)@en[[[Accept-Encoding:]]]] に [CODE(HTTP)@en[[[sdch]]]]
を入れてきますね・・・。 [TIME[2011-02-05T11:47:11.00Z]]

[5] [CITE[SDCH | Google グループ]]
( ([TIME[2011-02-05 20:45:56 +09:00]] 版))
<http://groups.google.com/group/SDCH?pli=1>

[6] [CITE@en[Shared Dictionary Compression Over HTTP - Wikipedia, the free encyclopedia]]
( ([TIME[2011-01-06 15:06:11 +09:00]] 版))
<http://en.wikipedia.org/wiki/Shared_Dictionary_Compression_Over_HTTP>

[7] [CITE@ja[Shared Dictionary Compression Over HTTP (SDCH)について - おぎろぐはてブロ]]
( ([[Ippei Ogiwara]] 著, [TIME[2014-11-19 23:14:05 +09:00]] 版))
<http://blog.hmm.jp/entry/sdch-shared-dictionary-compression-over-http>

[8] ( ([TIME[2011-01-12 13:46:42 +09:00]] 版))
<http://www.blogs.zeenor.com/wp-content/uploads/2011/01/Shared_Dictionary_Compression_over_HTTP.pdf>

[9] [CITE[A Proposal for Shared Dictionary Compression over HTTP]]
( ([TIME[2013-04-18 13:56:33 +09:00]] 版))
<http://lists.w3.org/Archives/Public/ietf-http-wg/2008JulSep/att-0441/Shared_Dictionary_Compression_over_HTTP.pdf>

[10] [CITE[Google で Proxomitron が機能しないのを回避するフィルタ - @think49の日記]]
( ([TIME[2014-10-18 08:22:43 +09:00]] 版))
<http://d.hatena.ne.jp/think49/20110514/1305348076>

[11] [CITE@en[641069 – Implement SDCH]]
( ([TIME[2014-11-19 23:32:42 +09:00]] 版))
<https://bugzilla.mozilla.org/show_bug.cgi?id=641069>

[12] [CITE@en[Re: A proposal for Shared Dictionary Compression over HTTP]]
( ([[Jon Butler]] 著, [TIME[2008-09-11 01:31:59 +09:00]] 版))
<http://lists.w3.org/Archives/Public/ietf-http-wg/2008JulSep/0452.html>

[13] [CITE[Notification of minor change to the SDCH spec. - Google グループ]] ([TIME[2014-11-19 23:46:42 +09:00]] 版) <https://groups.google.com/forum/#!topic/SDCH/pb40l0vqwJI>

[20] [CITE[SDCH framework - Google グループ]]
( ([TIME[2014-11-19 23:59:05 +09:00]] 版))
<https://groups.google.com/d/msg/SDCH/G4eFEEGwzko/O738Oqau5YMJ>

[21] [CITE[Issue 423813002: Sdch view for net-internals - Code Review]]
( ([TIME[2014-11-19 23:59:27 +09:00]] 版))
<https://codereview.chromium.org/423813002/>

[22] [CITE@en[baranov1ch/node-sdch]]
( ([TIME[2014-11-19 23:59:40 +09:00]] 版))
<https://github.com/baranov1ch/node-sdch>

[23] [CITE[SDCH over HTTPS - Google グループ]]
( ([TIME[2014-11-20 00:00:56 +09:00]] 版))
<https://groups.google.com/forum/#!topic/SDCH/8EEBFYMIB78>

[24] [CITE@en[draft-lee-sdch-spec-00 - A Proposal for Shared Dictionary Compression over HTTP]]
([TIME[2017-01-22 19:50:52 +09:00]])
<https://tools.ietf.org/html/draft-lee-sdch-spec-00>

[25] [CITE@en[641069 - (SDCH) Implement support for SDCH (Shared Dictionary Compression for HTTP)]]
([TIME[2018-02-04 11:30:57 +09:00]])
<https://bugzilla.mozilla.org/show_bug.cgi?id=641069>

[26] [CITE[Intent to Unship: SDCH - Google グループ]]
([TIME[2018-02-04 11:35:07 +09:00]])
<https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/nQl0ORHy7sw>