Mark Zuckerberg has long signaled that the future of Facebook will be off Facebook.com. His social network will take a big step toward that future at a developers conference in April.

That's when, according to a WSJ report, Facebook plans to launch a tool set for Web developers who want to make their off-Facebook Web sites look and work more like on-Facebook "pages."

On its site for Facebook developers, Facebook calls this toolset the "Open Graph API," and describes it this way:

The Open Graph API will allow any page on the Web to have all the features of a Facebook Page – users will be able to become a Fan of the page, it will show up on that user’s profile and in search results, and that page will be able to publish stories to the stream of its fans.

Facebook also provides the following "details":

The Open Graph API will allow any page on the Web to have all the features of a Facebook Page. Once implemented, developers can include a number of Facebook Widgets, like the Fan Box, or leverage any API, which enable the transformation of any Web page so it functions similar to a Facebook Page.

For example, AwesomeTees might decide that strategically they would like to locate their brand identity at www.awesometees.com. AwesomeTees will install the Fan Box widget, which will allow any Facebook user to "Become a Fan" of AwesomeTees, thereby establishing an official connection to AwesomeTees. The user will then have AwesomeTees listed in their list of connections on their profile as Pages are represented today. Additionally, any content that AwesomeTees publishes on AwesomeTees.com will show up in the stream on Facebook like it normally would. And, any time the user searches on Facebook, AwesomeTees will show up in the typeaheads and prominently in search results.

At the Wall Street Journal, Jessica Vascellero writes that Facebook's goal here is to "make it even easier for users to share information from the Web on Facebook and to have that information associated with their Facebook identity."

This move to expand Facebook beyond the domain of Facebook.com has been under way since Fall 2007, when Mark came to New York, announced that advertising changes every 100 years, and launched Facebook Beacon. Facebook Beacon transmitted Facebook user activity from third-party sites back to Facebook. The product quickly flopped, mostly because it wasn't opt-in.

Facebook re-branded the technology behind Beacon as an opt-in service called Facebook Connect in fall 2008 and launched it as a tool that allows Facebook users to sign into third-party sites using their Facebook IDs. Facebook Connect has been a huge hit.

In the year since Facebook Connect launched, more and more major brands have begun driving traffic not to their own domains, but to their branded Facebook Pages. These pages are attractive brands because once Facebook users become fans of a page, that page is free to update that friend regularly. It has been the return of email marketing. The Open Graph API, which will take Facebook fan pages out of Facebook without sacrificing these marketing tools is the next logical step.

The other two big reasons Facebook wants to expand beyond Facebook.com and onto third-party sites is that 1) there is hope within Facebook's executive ranks that the company can someday launch an ad network 2) Facebook would love to find itself in a position to offer e-commerce sites Facebook Connect-like "Pay With Facebook" one-click option. Some Facebook executives believe this business could eventually be larger than Facebook ads.

Now, don't miss our explosive exposé on the founding of Facebook: