Element - Entity Relationship Diagram

Use

The entity-relationship model's diagram based on Peter Pin-Shan Chen's classic approach. You can use the ER diagram to model a submodel of the conceptual schema. Entities are shown as nodes and relationships are shown as edges. The user selects the ER diagram notation in the application menu in Options which applies to all models.

Innovator supports the following diagram notations:

James Martin (crow's foot)
Chen (min,max)
Data Structure Analysis (DSA)
Unified Modeling Language (UML)
Structured Entity Relationship Model (SERM)

The main difference between these notations is how they display relationships, whose cardinalities are illustrated with various different graphic icons or formal texts in different places. SERM notation arranges entities in a sort of hierarchy from left to right.

Views can also be displayed as nodes and their From clauses as edges.

Attention:

SERM notation changes how nodes are arranged in the diagram if they were not previously set out in a SERM-compliant way.

Opening the diagram as read-only temporarily changes the layout to comply with SERM but does not save it.

Elements in an Entity Relationship Diagram

The following model elements can be shown as nodes and edges in entity relationship diagrams:

Icon	Element	Description
	Entity	An entity is the set of entities of the same type of the technical world to be modeled. Entity set describes this well but the term instance is common place when talking about an entity in this set.
	View	A view combines the attributes of one or more entities in a table. This may mean that a view's rows contain redundant data.The term attribute set will be used as an umbrella term for an entity or view.
	Attribute	An entity's attributes describe an instance's properties.
	Alternative Key	A key is a subset which can uniquely identify attributes of its entity using their instance. If the key attributes' value remains forcibly unchanged throughout the whole lifecycle, this is a so-called key candidate. The primary key which is best suited for implementing a relationship using a foreign key is chosen from the key candidates. If an entity in the real world does not have any key candidates, an artificial key which contains an integer attribute especially modeled for this is normally defined.
	View Attribute	The values of view attributes are obtained from values of the attributes used. This means that it is also possible for calculation expressions with functions to be used.
	Value Verification	A value verification constrains the possible values of attributes. It is the pendant to an SQL check constraint from the DB model.
	1:C
	1:MC
	1:M
	C:MC
	C:C
	R type	An R type is technically a relationship. These entities are needed to ensure the first normal form in a model that should be mapped onto a relational database. This is typically m:n relationships.
	M:M
	M:MC
	MC:MC
	Generalization	Generalization links two entities making one super and one sub. You can also talk about subordinate and superordinate entities.
	Key, ...