Understanding Your Data Model › Using Relations › Relation Usage Groups

Relation Usage Groups

Depending on how they operate within a data model, CA 2E relations are grouped under three different usage groups:

• Definition relations, which declare files to exist
• Key relations, which define the keys that identify a file by reference either to the keys of another CA 2E file or to a field
• Attribute relations, which declare the non-key fields that are present in a file by reference either to another file or to a field

The use of specific CA 2E relations allows for the physical arrangement, selection, and retrieval of information based on the arrangement of key fields in the database. The relations you choose determine which fields are to appear on which file, whether a field is a key field or foreign key field, and whether certain fields can be shared between files.

You must use the appropriate CA 2E relation types to describe a file-to-file or file-to-field relation respectively.