1. In a computer system having a graphical user interface and a data storage subsystem in which data items are organized and queried by way of metadata properties, a computer-implemented method of assigning values to properties, comprising: displaying a property tree, the property tree having a plurality of nodes exposing properties of a set of data items, said property tree including a carousel control for displaying a plurality of subnodes parented by one of the plurality of nodes; and in response to user input indicative of an assignment of at least one property exposed by the property tree, modifying the value associated with the at least one property in the data storage subsystem.