A data field represents a single data item and is the only data element provided by the toolkit that has a value. Each one has a value instance variable for storing the value of the data item. Because the toolkit accesses data held in a data field using the field's name, the name for the data field name should be unique. The data field attributes "value" and "description" can be overridden by another reference data.

The com.ibm.btt.base.DataField class is the implementation provided by the toolkit. The toolkit uses the <field> tag to externalize data fields.