Yahoo is swinging the doors of its Web platforms wide open to let outside developers create applications across its network of sites, as well as radically stitching together its online services under the social profile concept.

The idea is to let the hundreds of millions of people who use its Web mail, instant messaging, calendar, photo management and other online services replicate the social experience that social networks like MySpace and Facebook have made so popular.

This means that Yahoo users will have a profile under which their Yahoo services will fall, and which users will be able to customize by adding applications. This profile will also simplify the map of connections between Yahoo users so that they can find each other and interact more easily and efficiently.

If Yahoo is able to bring this vision to reality, it could pose a major threat to the appeal of MySpace, Facebook and other social networks, and give Yahoo the boost it has been seeking for years among Web users.

"It is rewiring Yahoo from the inside out, across all of our properties, to fundamentally open up those Web services and provide a consistent development model, a consistent deployment and consumer experience as well," said Ari Balogh, Yahoo's chief technology officer, during a keynote at the Web 2.0 Expo in San Francisco on Thursday.

While Yahoo has had open APIs (application programming interfaces) for a variety of its services for years, Balogh said this initiative will take those efforts to much greater lengths, and it will include streamlining the development process so that it's uniform for developers across Yahoo platforms, he said. "It includes opening it up in a way we have never done before. It's about making the entire Yahoo experience more social," he said.

The process is already ongoing, as Yahoo on Thursday announced the opening up in beta of its Search Monkey development environment, which lets external developers customize Yahoo search results to make them, in theory, more relevant and richer with information. Yahoo had announced its intention to do this in February.

Yahoo expects to hit more significant milestones in its opening-up process throughout the year, he said.