Fulfilling a second major part of its promise to make the internal workings of its website more open, Yahoo is opening the interface for its address book for outside use.
The move could mean that Yahoo, struggling under business pressures but still a stronghold of web activity, could become more tightly tied to other web services. For example, a programmer starting up a social-networking site could use the interface to send invitations to a member's list of contacts stored at Yahoo.
"Our address book has, for a long time, been one of the top things developers wanted access to," said Chris Yeh, head of the Yahoo Developer Network. That's because, over the years, Yahoo users have filled it with billions of individual records.
Yahoo users have stored more than 500 million address books and the service is used by more than 150 million unique users each month, Yeh said. "A lot of our address books [are] constantly being updated. It's one of the biggest sources of contact information on the web," he said.
Opening the address book API (application programming interface) is the second major step taken so far in executing the Yahoo Open Strategy that chief technology officer Ari Balogh announced in April. The first step, in May, was opening the SearchMonkey project so that outside coders could make more creative use of Yahoo search results.
"The address book is the second proof point. This year, we'll show proof point after proof point," Yeh said.
Yahoo Open Strategy is an attempt to increasingly link the company with other internet activities rather than remain a sealed-off, if sprawling, internet domain. Through its Open Strategy, the company envisions outside programmers building web applications on Yahoo's site, Yahoo services being incorporated into outside applications and social-connection information within Yahoo being used more widely.
Whether Yahoo will succeed in capturing developer attention and becoming a more dynamic part of new developments remains to be seen. A lot of action — some complementary but much of it competitive — is also taking place at rivals such as Facebook, Google and any number of small Web 2.0 start-ups.
From the outside looking in
The address book move means outside websites will be able to read and write address book information — if a user grants permission through a Yahoo authorisation process.
A site with a gift registry could piggyback on the address book so that a person could tell contacts about a wish list of presents, for example, Yeh said. Or a site shipping packages to others could auto-complete the address fields on a web form.
Explicitly opening the service is more secure than one alternative that exists today, in which a third-party site asks a user for Yahoo login credentials so it can access the site and scrape the contact information.
"There's no control over what happens after a user gives that [username and password]. The third party could use it to log in to mail or any other part of Yahoo," Yeh said. "It's not a real secure method."
Yahoo isn't opening up the interface for address book creation, however, which means it won't, at least for now, be usable as a generic back end for a website's address book needs.
Social graph theft?
One interesting possibility raised by the opening of the interface is whether an outside company might use it to steal, in effect, a user's social graph — the collection of connections each user must often laboriously reproduce as he or she joins a new site. Social graphs are a key asset of websites with a social element, in part because it's hard to reproduce them elsewhere. So once a user constructs one, there's a strong incentive to remain loyal to a site.
Yahoo isn't concerned about that, in part because opening the interface will mean other sites will be able not only to extract contact information from Yahoo but also to synchronise changes on their sites back with Yahoo, Yeh said.
"I don't think we're worried about losing control over our social graph. All the things we're doing now are trying to break down some of the traditional walls Yahoo has had to the outside world," he said. "Yes, absolutely, some of our data will get pulled out and be used for benefit of other systems. [But], when people use our system address book APIs, there's just as much a chance somebody will load something back into our network."
One company making use of the Yahoo address book interface is Plaxo, which hosts 40 million users' address books already.
Yahoo itself maintains multiple social graphs — for example, the address book, the Yahoo Messenger buddy lists, and the Flickr lists of contacts, friends and family.
"Not all this data is combined yet," Yeh said, although one key part of Yahoo Open Strategy is to unify these contact lists and the related user profile pages. "The goal of the next half year is to make sure we bring that together."
The Yahoo address book is the "place we like people to store all their contact information", Yeh said, but it's not a terribly rich social graph. For example, it doesn't currently have a good way to distinguish which contacts would be appropriate to invite to a new social service or to receive gift-registry notifications.
"One of the things that we have to do is give users an opportunity to activate their social graph a little bit — essentially, to make sure they can classify the people they're most interested in communicating with on a regular basis so we know how to create a social environment around them," Yeh said.
"Going forward, we'll have to have a better solution for people so we can classify inside our address book who we're closest to and who are at further distance from us," he added. "That's a function of the social work we're doing."
