Associations and Association Links (CDM)

In the Merise modeling methodology an association is used to connect several entities that each represents clearly defined objects, but are linked by an event, which may not be so clearly represented by another entity.

Each instance of an association corresponds to an instance of each entity linked to the association.

When you generate a PDM from a CDM, associations are generated as tables or references.

In the following example, three entities VIDEOK7, CLIENT, and STORE contain video cassette, client, and store information. They are linked by an association which represents a video cassette rental (K7RENTAL). The K7RENTAL association also contains the attributes DATE and STAFF_ID, which give the date of the rental, and the identity of the staff member who rented out the video cassette.



When you generate a PDM, K7RENTED is generated as a table with five columns, STORE_ID,K7_ID, CLIENT_ID, DATE, and STAFF_ID.



You can use associations exclusively in your CDM, or use both associations and relationships.

Association Links

An association is connected to an entity by an association link, which symbolizes the role and the cardinality between an association and an entity.