Data mapping techniques are disclosed. A representation of a first destination data field to which data is to be mapped is provided via a displayed user interface. One or more other destination data fields are not displayed at the same time as the first destination data field is displayed. A user input comprising a selection of a source data input field to be used to determine a data value for the first destination field is received. The displayed user interface is updated to include a representation of the selected source data input field and a control, wherein user interface code with which the displayed user interface is associated is responsive to provide via the displayed user interface a set of structurally valid options to further define how the data value for the first destination field is to be determined.