The XSDSchemaFile defines the column types for the tables and sets up the Master-detail relationship. The XMLFileName contains the data for both. The XMLData will appear in the DBWebGrids both at design time and runtmie. In this case, AutoUpdateCache is set to true, so changes will be saved to the XMLFileName as they are made. For this reason, there is no need for an ApplyButton, and UNDO will never work, as the changes will not be cached.