Borrowing a playbook from Sun's Java, Google is announcing a way for programmers to build social applications for multiple Web sites at once.

Google's version of this "write once run anywhere" concept is called OpenSocial, a set of common application programming interfaces (APIs) that will enable developers to create applications for social networks, blogs and any Web sites that accept the OpenSocial code. Currently, developers have to write new programs for each site, even if the functionality will be the same on each site.

This initiative "marks the first time that multiple social networks have been made accessible under a common API," according to a Google statement.

Facebook recently opened up its platform to developers and the site was immediately flooded with all sorts of useful and not-so-useful apps. Google, Yahoo and others have been heavily espousing the beauty of open platforms and making moves to that end.

Google's social network, Orkut, is among the sites that will accept apps written using OpenSocial APIs, as is LinkedIn, hi5, iLike, Slide, Ning, Friendster and Plaxo.

Facebook, which recently chose Microsoft over Google for an exclusive ad and investment deal, is not one of the OpenSocial-enabled sites.

A Google representative would not say whether Google had talked to Facebook and MySpace about joining the initiative or comment on why they were not involved.

The OpenSocial resources for developers and Web sites will be available at code.google.com/apis/opensocial.