Google is expected to announce Thursday that it will release an API that allows developers to create a single application that works across several social networks.

So far the Mountain View, Calif. search giant will "open up" its own Orkut. Ning, Plaxo, Friendster, viadeo, Hi5, LinkedIn and Oracle have also agreed to open their networks to the API.

Called OpenSocial, the platform is actually three separate APIs which handle profile information, friend/social graph data, and activity data. All a social network needs to do to participate is start accepting the API calls, and the information can be used by another application.

However, the information can't exactly access data from one social network to another, so this isn't quite yet the start of interoperability between social networks. However, it will make it much easier for developers to create applications for several social networks at once.

While Google is lacking the big names including MySpace and Facebook, it does have most of the major secondary networks under its belt. Additionally, it has attracted Facebook developers like Flixster and Slide to start developing under OpenSocial.

The search company expects that the common API will help to spur development of applications for social networks, and move them beyond the traditional add-ons which typically hold personal entertainment value and nothing more.

"The timing of OpenSocial couldn't be better," Michael Arrington wrote for TechCrunch Tuesday. "Developers have been complaining non stop about the costs of learning yet another markup launguage for every new social network platform, and taking developer time in creating and maintaining the code."