WebFinger

[1] WebFingerProtocol - webfinger - the WebFinger protocol - Personal Web Discovery, making email addresses readable again - Google Project Hosting ( (2011-08-27 11:59:22 +09:00 版)) <http://code.google.com/p/webfinger/wiki/WebFingerProtocol>

[2] RFC 7033 - WebFinger (2014-10-26 16:32:10 +09:00 版) <https://tools.ietf.org/html/rfc7033>

[3] WebFinger ( (2014-01-15 08:57:12 +09:00 版)) <http://webfinger.net/>

[4] シリコンバレー101 (331) Gmailアドレスが変わる! Google社内で「WebFinger」にゴーサイン | マイナビニュース ( (Mynavi Corporation 著, 2014-12-04 12:56:35 +09:00 版)) <http://news.mynavi.jp/column/svalley/331/>

[5] WebFinger - IndieWebCamp ( (2014-11-25 15:05:53 +09:00 版)) <http://indiewebcamp.com/WebFinger>

[6] remoteStorage ‒ An open protocol for per-user storage on the Web (2016-07-18 04:17:28 +09:00) <https://remotestorage.io/>

In order for apps to know where to ask permission and later actually sync user data, users give them a user address, basically like with E-Mail or Jabber/XMPP. With that address, apps retrieve storage information for the username on that domain/host.