The OpenSocial platform is an effort to establish and maintain a "community-governed specification for building social applications across the Web," according to Yahoo's news release this morning.

That would solve a problem for Web developers, according to the release:

"Before OpenSocial, if a developer built a 'favorite photos' application to work on one social network, it would have to be built all over again to work on another site. OpenSocial tackles this problem at its technology roots, providing common 'plumbing' that lets social applications run on many different websites without requiring duplicate work from either developers or the websites."

The specifications developed through OpenSocial will be made available under a Creative Commons copyright license and intellectual property related to the effort will be managed by this new OpenSocial Foundation.

Caroline McCarthy at CNET has comment from Facebook -- the hugely popular social network that has become a major platform for application developers. The company has not committed to OpenSocial does not intend to join the foundation.

Last fall, Microsoft bought a 1.6 percent stake in Facebook for $240 million.

(Update, 12:54 p.m.: I asked Microsoft for a comment whether the company is planning to participate in the OpenSocial effort or the OpenSocial Foundation. The response? Not right now. Here's the official line, attributed to John Richards, director of Windows Live Platform: "We constantly evaluate our involvement in industry groups and look for opportunities where it's appropriate to join the dialogue, but have nothing to announce at this time.")

Today, Microsoft is taking steps to make a key piece of the social networking puzzle -- contacts lists -- interoperable across several networks. In a blog post this morning, John Richards, director of Windows Live Platform, announced:

"[W]e will be working with Facebook, Bebo, Hi5, Tagged and LinkedIn to exchange functionally similar Contacts APIs, allowing us to create a safe, secure two-way street for users to move their relationships between our respective services. Along with these collaborations, Microsoft is introducing a new website at www.invite2messenger.net that people can visit to invite their friends from our partner social networks to join their Windows Live Messenger contact list."

The move is aimed at improving data portability among online services owned by different companies -- a sore issue for online privacy advocates. A key question is who owns the data you enter into social networks, online e-mail and instant messenger services?

"We firmly believe that we are simply stewards of customers' data and that customers should be able to choose how they control and share their data," Richards wrote.

Kip Kniskern, a blogger at LiveSide.net, which closely tracks Microsoft's efforts in this area, explains what this development means in this post:

"Currently, in order to populate a social network with information about your friends from say your Messenger buddies list or your Windows Live Hotmail account, you would need to provide your user info (e-mail address) AND your password to the social network, which would then store in some fashion for some length of time that information as it logged into your mail or messenger account and imported your address book. Not an inherently safe operation, but that's the way it has been done."

Users have also taken matters into their own hands, running "screen-scraping" scripts that pull their contacts from one place to another. But these methods, Richards wrote, put "customers at risk for phishing attacks, identity fraud, and spam." The Windows Live Contacts API is a safer alternative, he wrote.

Kniskern gave Microsoft props for this move.

"While there might be some advantage to partnerships such as these being in effect promotions of the Windows Live services on other sites, the security gained by doing the right thing here is to be commended," he wrote.