* 歴史

[1] [CITE[IRC logs: freenode / #whatwg / 20100121]]
([TIME[2010-01-23 15:13:04 +09:00]] 版)
<http://krijnhoetmer.nl/irc-logs/whatwg/20100121#l-168>

[2] [CITE[IRC logs: freenode / #whatwg / 20110609]]
( ([TIME[2011-06-16 23:01:17 +09:00]] 版))
<http://krijnhoetmer.nl/irc-logs/whatwg/20110609>

[3] [CITE@en[Web Applications 1.0 r6668        Redefine itemtype='__&&'&&__ to allow multiple types if they share the same vocabulary. This was by far the most frequently made request at the recent schema.org event]]
( ([TIME[2011-10-12 09:13:00 +09:00]] 版))
<http://html5.org/tools/web-apps-tracker?from=6667&to=6668>

[4] [CITE@en[Web Applications 1.0 r6793  itemtype can't be empty]]
( ([TIME[2011-11-01 12:13:00 +09:00]] 版))
<http://html5.org/tools/web-apps-tracker?from=6792&to=6793>

[5] [CITE@en[Web Applications 1.0 r6807      Remove the requirement that UAs check that item types are syntactically correct after splitting the itemtype='__&&'&&__ attribute.]]
( ([TIME[2011-11-02 01:27:00 +09:00]] 版))
<http://html5.org/tools/web-apps-tracker?from=6806&to=6807>

[6] [CITE@en[Web Applications 1.0 r4066 Update microdata based on results of usability study]]
( ([TIME[2009-10-03 06:44:00 +09:00]] 版))
<http://html5.org/tools/web-apps-tracker?from=4065&to=4066>

[7] [CITE@en[Fix #208: remove the Microdata API · whatwg/html@2aaecb8]] ([TIME[2015-10-07 20:13:43 +09:00]] 版) <https://github.com/whatwg/html/commit/2aaecb89900b875b9ee8357fa8bccf48477358bb>

[8] 
[[Google Search Console]]
の(自動)チェッカーは
[CODE[itemtype]]
に [[Schema.org]]
でない未知の値が指定されているとエラーを出してきます。警告ではなくエラーです。
何もしてなくても検出するといちいちメールで通知してきます。

[9] 
[[Schema.org]] でなくても [[HTML]] 的にはまったく正当なのに、
[[Google]] が知らないからといってエラーにするのは迷惑すぎませんか。
[TIME[2023-01-15T02:13:02.0Z]]