Composite relationships are always one-to-many.įorward and backward path labels describe the relationship when navigating from one object to another. Once a pole is deleted, a delete message is propagated to its related transformers, which are deleted from the transformers' feature class. For example, power poles support transformers, and transformers are mounted on poles. Simple relationships can have one-to-one, one-to-many, or many-to-many cardinality.Ī composite relationship is one in which the lifetime of one object controls the lifetime of its related objects. However, a railroad crossing can exist without a signal lamp, and signal lamps exist on the railroad network where there are no railroad crossings. For example, in a railroad network, you might have railroad crossings that have one or more related signal lamps. Simple or peer-to-peer relationships involve two or more objects in the database that exist independently of each other. One-to-one and one-to-many relationship classes can also have attributes in this case, a table is created to store the relationships. An attribute of that relationship could be percentage ownership.
For example, in a parcel database, you might have a relationship class between parcels and owners in which owners "own" parcels and parcels are "owned by" owners. This table can also have other fields to store attributes of the relationship itself that are not attributed to either the origin or destination class. Once created, a relationship class cannot be modified you can only add, delete, or refine its rules.įor many-to-many relationship classes, a new table is created in the database to store the foreign keys used to link the origin and destination classes. Relationships can exist between spatial objects (features in feature classes), nonspatial objects (rows in a table), or spatial and nonspatial objects.