A computing device displays a data visualization user interface that includes a schema region. Each data field displayed in the schema region is visually associated with a respective data object of a plurality of data objects in an object model. The device receives user input to specify a mathematical expression that includes a first data field from a first object and a second data field from a second object. The first object and the second object are distinct objects in the object model. The device generates a calculated data field based on the mathematical expression. The device assigns the calculated data field as a member of a third object in the object model according to relations in the object model connecting the first object to the second object. The device displays the calculated data field, in the schema region, visually associated with the third object.