[youtube http://www.youtube.com/watch?v=LabCylbapuM&rel=1&border=1]

Google is building social data out of existing behavior on the web — linking to a blog from your blog, for example — to create a single sign-on experience for any web site. The initiative, called the Social Graph API, will make it easier for people to quickly create social relationships anywhere they want. So when you sign up for, say, a startup’s new web service, the startup can ask you if you want to include these “friends” to be friends on your new site.

This is Google’s latest effort to be social like a social network. Across many fronts, it is trying automate the process of creating an online network of friends. The company already automatically adds IM connections between you and the people you email, on Gchat within Gmail. Then it uses this information for other services, like showing your shared items in Google Reader to all of these people. The company is also experimenting in social search, as we recently covered, where it is experimenting with ideas such as giving you tailored search results based on your relationships in Gmail.

The so-called Social Graph API uses the same algorithms as the Google search engine, crawling publicly available web pages to identify links between you and others. It aggregates web links that contain code for a tag standard called XHTML Friends Network (XFN), that explains who is sending the link and if the person being linked to is a friend, or a standard called Friend-of-a-Friend (FOAF) which explains who friends of friends are related.

The two standards provide public data about you and who you know. Users will be able to control this service, so you can manually remove people who you don’t want to include. Read more about it on Google engineer Brad Fitzpatrick’s post here.

One can also imagine new opportunities for developers to build applications using the Open Social application standard, where an application could both contain information about your relationships from the Social Graph API and appear anywhere on the web.

See Techmeme for more coverage of the announcement.

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