Web 2.0 refers to a second generation of web-based communities and services that encourage collaboration and sharing among users. Key aspects of Web 2.0 include social networking sites, wikis, blogs, and folksonomies. Library 2.0 applies these interactive and collaborative web technologies to library services and collections, making them more user-centered and dynamic. Examples include replacing email reference with chat reference, and augmenting controlled classification schemes with user tagging. The goals of Library 2.0 include building communities and allowing innovative changes to library services.