In an aggressive move, MySpace will open its users’ public activity stream data to external developers, so that third-party applications and Web sites are able to display these status updates and action notifications.

The activity stream data will become available to external developers via a new set of APIs (application programming interfaces) that MySpace plans to release on Wednesday.

“We have one of the larger real-time streams available on the Web,” said Mike Jones, MySpace’s chief operating officer. “We’re giving full public access to that real-time stream to any developer who wants to ingest it.”

The about 110 million MySpace users worldwide generate about 46 million status updates and action notifications every day, such as when they post a message, add someone to their friend list, upload photos or videos, build a playlist or add a song to their profile.

With this move MySpace is tapping into the popular trend established by social network and microblogging service Twitter, where people and organizations post short text messages, most of them public, on every conceivable topic, whether commenting on news, updating friends on their whereabouts or promoting goods and services.

Twitter from early on has made its stream data available to external developers, so that a thriving and vibrant ecosystem of third-party applications exists for Twitter users.

MySpace was once the world’s most popular social-networking site but lost its crown to Facebook, as the latter lured users with a cleaner interface, more granular privacy settings and a platform with tens of thousands of third-party applications.

MySpace parent company News Corp. has shaken up its management this year in the hopes of jump-starting the site. News Corp. brought in former Aol CEO Jon Miller in April to be chairman and CEO of its Digital Media Group and its chief digital officer, overseeing the company’s Internet businesses, including MySpace. Miller then tapped former Facebook executive Owen Van Natta to replace MySpace CEO Chris DeWolfe.

Since then, News Corp. has cut MySpace’s staff in the U.S. and abroad, while trying to refocus the site on its traditional strengths of music and entertainment, while tapping into hot trends like microblogging.

In October, Miller said at the Web 2.0 Summit in San Francisco that he was “obsessed” with real-time notification technology like the one Twitter has popularized, and that he wanted to see MySpace incorporate it. At that event, Miller also said MySpace’s application was “too closed” to external developers, and that he hoped to see that changed.