If you’re like most of us, you probably have contact and address book data spread all over the web — friends on Facebook, contacts in Gmail, followers on Twitter, and names in your local address book application.

Wouldn’t it be nice if all that data were available in one place where you could see it all, control which sites have access to it and manage your on and offline friends?

The truly unified address book is still a ways off, but there is hope it will be especially useful once it arrives thanks to some emerging standards.

The Worldwide Web Consortium (W3C), the governing body that creates and oversees web standards, has published a working draft of what’s known as the Contacts API. The goal behind the Contacts API is to provide a way to unify your address book, pulling from both local and online sources, and to allow you to better control how third-party websites access your data.

The latest draft incorporates feedback based on the earlier draft, first published back in January of 2010. It builds upon the work being done on vCard and Portable Contacts, among other contact systems already being used on the web. The final version is penciled in for mid-2011.

The Contacts API is part of a broader initiative at the W3C called the Ubiquitous Web Applications activity. The purpose of the group is to develop underlying infrastructures web services can take advantage of to make web apps more powerful and more useful. The Geolocation API, which lets a web app learn your location, and the Devices API, which lets a web app access a camera or microphone in your hardware, are also part of the same initiative. It also fits into the ideals outlined by the W3C’s vision of a semantic web.

So what will the Contacts API standardize? Currently, if a site wants to access your contacts list it generally does so by grabbing, say, your whole Gmail contacts list. Even with standards like OAuth, which gives you control over which sites can access your contacts list, you still don’t have much in the way of fine-grained permissions.

Say you want Facebook to only grab contacts that you’ve put in the address group “friends” in your Gmail address book. With the current controls, you’re out of luck. But if and when the Contacts API is ratified and adopted, that’s exactly the sort of thing it would allow you to do.

The Contacts API would also give the browser a method of unifying all your various contacts lists — for example your contacts from Gmail, Facebook and your local address book all merged to single list.

It sounds grand, no doubt, but the Contacts API is a long way from reality. Mozilla has experimented with the API (along with other tools) to create the Labs project Contacts, but like the APIs it uses, Contacts is still very much a work in progress.

See Also:

• Mozilla Contacts Helps Firefox Discover Your Social Web
• Mozilla Labs Seeks to Tame Your Address Book With ‘Contacts’
• New Google Contacts API Taps Your Gmail Address Book
• Access Your Gmail Contacts From Any Site