Adding primary keys

A primary key is the attribute or minimal combination of attributes which
uniquely identifies each occurrence of an entity.
Primary keys can be created in two ways: by using the toolbar or by directly entering
the information in the model’s properties window.
Example: employee number, company code, department number.
- Select the key tool
in the Open ModelSphere toolbar.
- Choose the attribute that you want to designate as a key. The attribute will
be underlined to denote that it is a primary key attribute. (If you pick the
wrong attribute, use the Key tool to remove the underline)
Remember that primary keys can be composed of multiple attributes. Simply
select the additional attributes that will be part of the key.
- Add the primary keys to your diagram as shown in the following conceptual data model.
In Open ModelSphere, primary keys are underlined to distinguish them from
other attributes. In the example above, all four entities have a primary key composed
of a single attribute. For example, in the Project entity, Team project’s number is used
to identify each project, and Employee number uniquely identifies each employee in
the Employees entity.