Relationships (CDM/LDM)

A relationship is a link between entities. For example, in a model that manages human resources, the "Member" relationship links the entities Employee and Team and expresses that each employee works in a team, and each team has employees.

An occurrence of a relationship corresponds to one instance of each of the two entities involved in the relationship. For example, the employee Martin working in the Marketing team is one occurrence of the relationship Member.

When you generate a PDM from a CDM or LDM, relationships are generated as references.

• Creating a Relationship
  You can create a relationship from the Toolbox, Browser, or Model menu.
• Relationship Properties
  To view or edit a relationship's properties, double-click its diagram symbol or Browser or list entry. The property sheet tabs and fields listed here are those available by default, before any customization of the interface by you or an administrator.
• Enabling Many-to-many Relationships in an LDM
  In an LDM, many-to-many relationships are, by default, not permitted and are represented with an intermediary entity. If you allow many-to-many relationships, you can select the many-to-many value in the cardinalities tab.
• Creating a Reflexive Relationship
  A reflexive relationship is a relationship between an entity and itself.
• Defining a Code Option for Relationships
  You can control naming restraints for relationships so that each relationship must have a unique code.
• Changing a Relationship into an Associative Entity
  You can transform a relationship between two entities into an associative entity linked by two relationships, and then attach entity attributes to the associative entity that you could not attach to the relationship.
• Relationship Examples
  This section shows the graphic representation of various relationship properties.
• Identifier Migration Along Relationships
  Migrations are made instantaneously in an LDM or during generation if you generate a PDM from a CDM.