Objects and relations that can be drawn in an ERD view are based on the elements available to the open view.
Objects and relationships can be added in different ways, by using:
- the Create pane
- the quick-create pop-up window
- the model browser
- the quick-create object controls
- the smart connector
- the context menu
For detailed information about the possible ways to add objects and relationships, please refer to Creating objects and relations.
Elements for modeling
Several elements are available for entity-relationship modeling. Their availability depends on the view you are modeling in; the amount of detail that can be put into a model depends on the level at which you are modeling. Globally, the following elements can be used:
- Entities for describing the components/objects in the data model. Entities represent persons, places, items, events, or concepts.
- Attributes for describing the properties of an entity. Attributes have an optionality and a key.
- Keys for identifying the uniqueness of attributes.
- Facts for displaying the relations between entities in a NIAM view.
- Different types of relations for displaying the connections between elements the different views. Relations may know a cardinality (multiplicity), an optionality (participation), and roles. By means of specialization relations entities can be subtyped.
- Constraints for describing limitations that can be assigned to roles in a NIAM view.
For a detailed overview of the available elements including an example, see Elements for ERD modeling.
In addition to the elements that are specific to the modeling language or method, there are several graphic shapes that can be included in a diagram or view. These graphic shapes are generic and available in each modeling language and method in Enterprise Studio.
Separate submodels within the model
Within an entity-relationship model, Crows Foot views and NIAM views can be modeled next to each other, but they are considered separate submodels. It means that elements modeled in a Crows Foot view cannot be used in a NIAM view, and reverse.
The entities in both types of views also have different colors. In the model browser, the elements of both submodels are located in separate containers called "Crows Foot model" and "NIAM model", as is shown in the following figure.
It is possible to use elements in multiple views of the same type, so in various Crows Foot views, or in various NIAM views.
The entities and attributes in an ER logical view and NIAM view have controls that can be used to characterize and mark them or provide them with specific information. The conceptual view does not have any ERD-specific controls. Some of the controls appear when you click an entity or attribute, and some are always visible. Example:
Example of object controls on an entity
Click the control to perform the operation. For an overview of the available controls, see Controls for the ERD objects.