On Friday at Yahoo's San Francisco satellite office, known as the Brickhouse, a group of Yahoo executives and product managers presented a preview of Y!OS, Yahoo's Open Strategy.

Last week, Yahoo released its "universal profile," the first consumer-facing element of its plan to rewire the company to leverage social interaction data across its properties and beyond. It's "a centralized control panel that lets you manage your identity, activities, interests, and connections across Yahoo -- and eventually the entire Web," as Jim Stoneham, Yahoo's VP of communities, put it in a blog post.

Next week, Ash Patel, head of Yahoo's audience product division, explained, Yahoo expects to introduce the Yahoo Application Platform, a framework for building Web applications for Yahoo and elsewhere; the Yahoo Social Platform, a set of application programming interfaces for utilizing social graph data and user activity streams; and Yahoo Query Language, for querying and manipulating data from Yahoo and other sources.

And in the coming months, the ripples of Y!OS will reach Yahoo's home page and Yahoo Mail, enabling functions and applications that utilize social profile data.

Yahoo's Open Strategy "is about changing Yahoo from a walled garden to the best of the Web," said Patel.

Jay Rossiter, head of Yahoo's Open Strategy, described it as a way to "bring a social dimension to what Yahoo does and open up Yahoo properties and the data they have, to allow developers to bring applications out to users, for a more engaging experience."

Yahoo says it has more than 500 million users worldwide.

Key to Yahoo's vision is OAuth, an open protocol for publishing and utilizing protected data. Yahoo has spent a significant amount of effort building OAuth into its infrastructure to provide users with a way to control how Yahoo Profile data gets shared. The idea is to put the user in charge of data sharing and to make data sharing choices obvious.

Neal Sample, chief architect of platforms at Yahoo, explained that when people let Yahoo or third-party applications make use of their data, they will be presented with a detailed summary of how their data will be used. By making data use explicit and requiring user agreement, Sample expects that developers will be discouraged from asking for more data than they need.

Yahoo clearly aims to avoid the privacy issues that surfaced after Facebook introduced Beacon, a social ad targeting system in late 2007. Nevertheless, its reason for being is advertising revenue. The theory is that by making Yahoo more of a social experience and more open to third-party developers, Yahoo users and their online friends will spend more time on Yahoo's network and be more engaged. That, in turn, would bring greater advertising revenue.

And given the third-quarter financial results that Yahoo reported earlier this week, Y!OS can't come too soon.