On Friday of last week,  brad Fitzpatrick posted an entry on the Google code blog entitled URLs are People, Too where he wrote

So you've just built a totally sweet new social app and you can't wait for people to start using it, but there's a problem: when people join they don't have any friends on your site. They're lonely, and the experience isn't good because they can't use the app with people they know. You could ask them to search for and add all their friends, but you know that every other app is asking them to do the same thing and they're getting sick of it. Or they tried address book import, but that didn't totally work, because they don't even have all their friends' email addresses (especially if they only know them from another social networking site!). What's a developer to do?

One option is the new Social Graph API, which makes information about the public connections between people on the Web easily available and useful
...
Here's how it works: we crawl the Web to find publicly declared relationships between people's accounts, just like Google crawls the Web for links between pages. But instead of returning links to HTML documents, the API returns JSON data structures representing the social relationships we discovered from all the XFN and FOAF. When a user signs up for your app, you can use the API to remind them who they've said they're friends with on other sites and ask them if they want to be friends on your new site.

I talked to Dewitt Clinton, Kevin Marks and Brad Fitzpatrick about this API at the O'Reilly Social Graph FOO Camp and I think it is very interesting. Before talking about the API, I did want to comment on the fact that this is the second time I've seen a Google employee ship something that implies that any developer can just write custom code to do data analysis on top of their search index (i.e. Google's copy of the World Wide Web) and then share that information with the world. The first time was Ian Hickson's work with Web authoring statistics. That is cool.

Now back to the Google Social Graph API. An illuminating aspect of my conversations at the Social Graph FOO Camp is that the scenario described by Brad where social applications would like to bootstrap the user's experience by showing them their friends who use the service is more important than the "invite my friends to join this new social networking site" for established social apps. This is interesting primarily because both goals are currently achieved by the current anti-pattern of requesting a user's username and password to their email service provider and screen scraping their address book. The social graph API attempts to eliminate the need for this ugly practice by providing a public API which will crawl a user's publicly articulated relationships and then providing an API that social apps can use to find the user's identities on other services as well as their relationships with other users on those services.

The API uses URIs as the primary identifier for users instead of email addresses. Of course, since there is often an intuitive way to convert a username to a URI (e.g. 'carnage4life on Twitter' => http://www.twitter.com/carnage4life), users simply need to provide a username instead of a URI.

So how would this work in the real world? So let's say I signed up for Facebook for the first time today. At this point my experience on the site would be pretty lame because I've made no friends so my news feed would be empty and I'm not connected to anyone I know on the site yet. Now instead of Facebook collecting the username and password for my email address provider to screen scrape my addres book (boo hiss) it shows a list of social networking sites and asks for just my username on those sites. On obtaining my username on Twitter, it maps that to a URI and passes that to the Social Graph API. This returns a list of people I'm following on Twitter with various identifiers for them, which Facebook in turn looks up in their user database then prompts me to add them as my friends on the site if any of them are Facebook users.

This is a good idea that gets around the proliferation of applications that collect usernames and passwords from users to try to access their social graph on other sites. However there are lots of practical problems with relying on this as an alternative to screen scraping and other approaches intended to discover a user's social graph including

• many social networking sites don't expose their friend lists as FOAF or XFN
• many friend lists on social networking sites are actually hidden from the public Web (e.g. most friend lists on Facebook) which is by design
• many friend lists in social apps aren't even on the Web (e.g. buddy lists from IM clients, address books in desktop clients)

That said this is a good contribution to this space. Ideally, the major social networking sites and address book providers would also expose APIs that social applications can use to obtain a user's social graph without resorting to screen scraping. We are definitely working on that at Windows Live with the Windows Live Contacts API. I'd love to see other social software vendors step up and provide similar APIs in the coming months. That way everybody wins; our users, our applications and the entire ecosystem.

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