System Architect provides the capability to build multiple project data models in a single project encyclopedia. Each Project Data Model can consist of a Model diagram and one or more Subject Area diagrams. Models and subject area diagrams are always either Components of an entity relation diagram (ERD) or IDEF1X diagrams.
Note A Project Data Model is not a diagram. There is no diagrammatic way to represent or “see” a project data model.
The Model diagram encompasses all of the entities and relationships contained within the project data model. The Model diagram is built upon subordinate Subject Area diagrams. Each Subject Area diagram represents a piece of the Model diagram. A change made to a Subject Area diagram is automatically reflected in the Model diagram. A change to the Model diagram is not necessarily reflected in any Subject Area diagram.
For example, if you delete entity A from a Subject Area diagram, you are asked whether it should be deleted from the Model diagram as well. But if you delete entity B from the Model diagram, it is automatically deleted from any Subject Area diagram on which it is drawn. Any entity or constraint on a Subject Area diagram must be on the Model; any entity or constraint may be on the Model and not on any Subject Area diagram.
The project data model includes definitions of the diagram’s component pieces:
▪Entity Types to represent each person, place, event, or concept for which information will be maintained in the system.
▪Attributes to represent each named characteristic of an entity.
▪Access Path to specify the attributes that can be used to locate an individual record that is represented by an entity.
▪Relation Lines to represent each association between entities in the model.
Physical data models can be from ERDs and IDEF1X diagrams.