CA 2E Quick Tour › Defining Data Models › Relationship Extension

Relationship Extension

One file can be associated with another by means of the Refers to relation. A file can also reference another file more than once or to itself. To distinguish among multiple references to the same file,CA 2E provides an extended form of the Refers to relation that lets you specify differences among the relations using For text.

In our example a horse’s parents are also horses. To record the horse’s parents, two HORSE Refers to HORSE relations—one for each parent—must be established as shown in the following illustration:

Because the HORSE file refers to itself more than once, you will need to use the extended form of the Refers to relation to distinguish between the two relations. For further details on how this is accomplished, see the Tutorial.