The public web is made up of linked pages that represent both documents and people.
Google Search helps make this information more accessible and useful. If you take away the documents, you’re left with the connections between people.
Information about the public connections between people is really useful — as a user, you might want to see who else you’re connected to, and as a developer of social applications, you can provide better features for your users if you know who their public friends are.
For long there hasn’t been a good way to access this information, however now The Social Graph API makes information about the public connections between people on the Web, expressed by XFN and FOAF markup and other publicly declared connections, easily available and useful for developers.
How does the Social Graph API find these connections ?
The Social Graph API looks for two types of publicly declared connections:
1. It looks for all public URLs that belong to you and are interconnected. This could be your blog (a1), your LiveJournal page (a2), and your Twitter account (a3).
2. It looks for publicly declared connections between people. For example, a1 may link to b’s blog while a1 and c link to each other.