A relationship leg is a link between a relationship and an entity or a subtype entity, whose characteristics are: the role, the cardinality and the average cardinality.
To create a relationship leg, select the Link tool from the CDM palette.
To modify the characteristics of a relationship leg, you must either:
Click a link on the CDM.
Click an item in the "Attached legs" section of the Create/Modify a relationship dialog box.
Displayed data
Link
Name of the two objects connected by the leg.
Data entry
Role
Clear description of the link's function.
Length: 50 characters maximum.
Optional entry.
Average cardinality
Average cardinality of the link.
If this field is informed, its value must range between the limits of the selected cardinality.
Optional entry.
Radio buttons
Cardinality
The cardinality is the main attribute of the link.
Values available:
"0,1"
"1,1"
"0,N"
"1,N"
Check boxes
Functional dependency-type leg (fd)
In the case of N-ary relationships, this check box specifies whether the connected entity is in functional dependency with the other entities taking part into the relationship.
The logical entity issued from the relationship during the logical model generation, has, as a key, the concatenation of the keys of the entities which take part into the relationship and are not in functional dependency towards other entities.
Checked |
The entity is in functional dependency with the other entities taking part into the relationship. Its key will be duplicated only as a property, in the logical entity issued from the relationship. |
Not checked |
The entity is not in functional dependency with the other entities taking part into the relationship. Its key will be duplicated in the logical entity issued from the relationship, and will be part of the entity key. |
Buttons
Enter/Create/Modify (validation)
The Enter button (in display mode) closes the dialog box.
The Create button (in creation mode) or Modify button (in modification mode) validates the dialog box.
The various fields of the dialog box are verified. If all are valid, the definition of the relationship leg is updated in the database before the box is closed; otherwise, an error message is displayed.
Cancel
This button closes the dialog box without validating the choices made.
Keyboard shortcut: Esc.