1. A system for providing a flexible and extensible metadata-driven user interface that combines deductive and task-based interfaces, the user interface having an inbox, the system comprising: a first data storage for storing a state of tasks of a user; a second data storage for storing metadata, the metadata identifying user interface elements and indicating properties relating to the user interface elements, the metadata enabling flexibility and extensibility of the user interface through additions and modifications of the metadata; and an inbox applet component that, when requested, provides a user interface having the inbox that enables the user to manipulate a task, the user interface generated from the second data storage, the inbox comprising items of the first data storage.