Composition of a user interface through data binding

The technology relates to integrating applications into a single user interface. One or more computing devices may display a user interface including associated data corresponding to a first application and generate a request for supplemental data. A second application which can satisfy the request for supplemental data may be identified by the one or more computing devices, and the one or more computing devices may generate and display a notification indicating that the second application can provide the requested supplemental data. A selection of the notification may be received by the one or more computing devices and a second user interface corresponding to the second application may be integrated into the user interface, wherein the second user interface displays the requested supplemental data.