Data Modeling: acknowledging the basic concepts
The basic concepts
Table : a relational table.
Column : an attribute of the table.
Association : a graphical representation of a relationship
between at most two tables.
Role : each side of the association. Qualifies each
table's implication in this relationship.
Role multiplicity : the number of occurrences of the
related table.
Role navigability : indicates if this table is a child
or a parent table.
Role constraint type : referential integrity implementation
mechanism.
Key: primary
, unique
or foreign
.
Key dependency: for primary and unique keys.
Referenced constraint: source of the foreign key
constraint. May be a primary or unique key.
Building a data model
A relational data model consists of tables with non-decomposable
columns and binary associations. A data model is used as a communication
vehicle to build and describe databases.
It is possible to create a data model from the main menu, from the explorer window
and from the edit toolbar.
- From the main menu, choose Edit > Add > Data model > target system of
your choice.
- From the explorer window, right-click project. Then, from the pop-up menu,
choose Add > Data model > target system of your choice.
- From the edit toolbar, look for the Add
tool , click it and choose Data
model > target system of your choice.
By default, a data model comes with a diagram. Here is how to display it:
- Click the handle
next to the data model in the explorer window, Diagram
will appear.
- Right-click Diagram.
- From the pop-up menu, choose Show diagram.
The diagram appears on the right side of the explorer window. If it is empty, right-click
inside the diagram window and from the pop-up menu choose Add Missing
Graphical Representations.
If you do not want the data model to be automatically created with a diagram,
change the default settings. See Modifying the options.
To add a target system, see Target system.