Facebook has revamped its application development platform to make it possible for the social-networking site and other Web sites to mesh what they know about their end-users and automatically personalise the experience people have online.

For example, a visitor to a participating news site or a music-sharing site could be served up content upon arrival based on previously stated preferences on Facebook or participating sites. The visitor could also see a list of Facebook friends who are already registered on the other site, and even what comments they have posted there.

"People can have instantly social and personalized experiences everywhere they go," said Mark Zuckerberg, Facebook's CEO, during a keynote speech Wednesday at the company's F8 conference for developers.

Making this possible is Facebook's Open Graph API (application programming interface), designed to allow Facebook and participating sites to blend their respective user "social graphs" to customize their site experience for each individual visitor.

Facebook is also releasing the Open Graph Protocol, a system to mark up objects in a uniform way so that they can be understood the same way by Facebook and third-party sites.

Facebook is also making available a series of iFrame plug-ins that developers can drop into their Web pages to re-create Facebook functionality, such as the "Like" button the company announced this week. This button lets end-users tell Facebook and external Web sites that they're interested in specific news articles, songs and other content.

Other functionality that can be replicated via plug-ins includes Facebook's activity stream and log-in operation as well as a new recommendation engine to generate personalized recommendations for site visitors.

While Facebook has been moving toward this vision for some time, the company has now significantly simplified the tools and processes for developers to build applications and Facebook integration into their sites, said Bret Taylor, head of Facebook Platform products. "The Facebook platform can be both powerful and simple," he said.

Gartner analyst Ray Valdes sees Facebook trying to translate its leadership position among social-networking sites into becoming the center of the evolving social Web at large.

"The goal is to put a coat of Facebook paint on every Web page on the public Internet, and connect these pages to the Facebook platform," Valdes said via e-mail.

"If this ambitious initiative is successful in gaining adoption, they could become the next Google," he said.

A big question mark is whether end-users will embrace the concept of an extended "social graph," where their profiles and actions on Facebook and other Web sites are consolidated and used to personalize their user experience.

"The uptake depends on the level of trust that users have in Facebook, and also the value that participating sites can deliver to users," Valdes said.

Facebook isn't the first company to pursue this "Web single sign-on" concept, and none has been successful. "Facebook is the first that has a real chance at gaining a foothold and holding on over time," he said.

For Jeremiah Owyang, an Altimeter Group analyst, the data aggregated through Facebook's Open Graph initiative represents the "foundation" for what he calls social CRM (customer relationship management), he said in a blog post.

Facebook's continued steps to tear down its walled garden put it in a better position to compete against Google, but could also alienate users who feel the site no longer offers the privacy protection it once did, according to Owyang.

"Facebook's roaring growth is a threat to Google and other web portals, and as more developers deploy these hooks, they spread their colonies all over the internet. Yet Facebook's core conundrum is they've made the promise to their users to keep the experience private and closed," Owyang wrote.

Among the partners joining Facebook in Wednesday's announcement is Microsoft, with which it built a joint site called Docs for Facebook users to collaborate on online documents. This, at first glance, looks like it could compete against the similarly named Google Docs suite of hosted office productivity applications. Other partners include customer review site Yelp and music site Pandora.

Facebook's goal is to move from a Web that's connected via hyperlinks to one "where the default is social" and has users with real identities at its center, Zuckerberg said.

Neither Zuckerberg nor Taylor spoke much about the implications, if any, of the announcements on users' privacy, always a big question for Facebook, where people store and share a lot of very personal information and content.