Relation properties include the following:

Property	Description
GetRowsEvent	This property is False by default. If set to True, the relation becomes custom. That means that it is not based on joins, equalities between table fields, but child rows are obtained by code in the GetChildRows event. It is used when you need a more complicated algorithm than simple equality of table fields. For example, see the CustomRelations sample in the Samples directory, where a custom relation is used to represent a many-to-many relation that cannot be based on a single simple relation between tables.
DeleteCascadeRule	This property specifies what happens to child rows when their parent row is deleted. None (default) means that child rows are left unchanged. As a result of deleting the parent row, they become orphan rows, without parent. The Cascade value means that child rows are deleted. Set this property to Cascade when child rows belong to their parent, should not exist without it. There are also two less frequently used values: SetNull meaning that child rows remain with related field(s) set to Null, and SetDefault meaning that child rows remain with related field(s) set to its default value.
UpdateCascadeRule	This property determines what happens to child fields when parent field values are changed. If it is set to Cascade (default), the child fields are changed correspondingly. If it is set to None, the child fields are left unchanged. If it is set to SetNull, the child fields are set to Null. If it is set to SetDefault, the child fields are set to their default values.