The user interface (UI) consists of the MediaWiki functionality by which the user obtains data from the wiki and makes changes to the wiki. The UI is generally considered separate from the API, a means by which data is obtained from or entered into the wiki in a machine-readable (viz. XML) form for use by, or by means of, applications that have their own user interfaces. The user interface can be configured, revised or extended by a variety of means, such as CSS files (including stylesheets), interface messages, and user interface extensions.