Developed by Google Inc., OpenSocial is a set of common APIs for building social applications across multiple Web sites, including social networking sites (SNS). OpenSocial applications use Google’s gadget architecture but with extensions that provide access to social data within its container environment. Similar to Google Gadgets, OpenSocial apps are hosted XML documents with HTML and/or JavaScript within their bodies. The OpenSocial API can be accessed on the client-side using the JavaScript API, and on the server-side by using RESTful data APIs. Some Web sites currently using OpenSocial include Friendster, hi5, LinkedIn, MySpace, orkut, Salesforce.com, and others.
See “Social Networking Sites” in the Quick Reference section of Webopedia.