Chen ER Diagram - Entity-Relationship Diagram in Chen Notation

Chen's notation of the entity-relationship diagram depicts data and domain models using entities, attributes, and relationships. Unlike other ER diagram notations, it shows attributes as standalone boxes, not as a part of entities.

Chen Diagram Symbols

Chen ER diagram offers these symbols:

Entity

An entity represents a set of objects with the same attributes within a data model. It is depicted as a rectangle.

Entity (Chen ERD)
Entity (Chen ERD)

Weak Entity

A week entity is a type of entity that does not have any unique key for the attribute tuples. A weak entity depends on another entity, that is considered its owner. It is depicted as a rectangle with a double border.

Weak Entity (Chen ERD)
Weak Entity (Chen ERD)

Associative Entity

An associative entity represents a many-to-many relationship that is expressed by another entity (or a table in database). It is depicted as a rectangle with a diamond inside.

Associative Entity (Chen ERD)
Associative Entity (Chen ERD)

Attribute

An attribute contains a piece of information that describes an entity. An attribute is depicted as an ellipse. There are these types of attributes:

Attribute (Chen ERD)
Attribute (Chen ERD)

Key Attribute

A key attribute represents an identifying attribute. The key attributes define a combination of keys that unambiguously define a tuple within an entity.

Key Attribute (Chen ERD)
Key Attribute (Chen ERD)

Weak Key Attribute

A weak key attribute (or partial key) is a attribute that in combination with owner's key creates a key for weak entity.

Weak Key Attribute (Chen ERD)
Weak Key Attribute (Chen ERD)

Multi Value Attribute

A multi value attribute can have multiple distinctive values. The attribute is represented by an array of values.

Multi Value Attribute (Chen ERD)
Multi Value Attribute (Chen ERD)

Derived Attribute

A derived attribute represents an attribute that does not physically exist in permanently stored form. It is an attribute that is calculated from other attributes.

Derived Attribute (Chen ERD)
Derived Attribute (Chen ERD)

Relationship

A relationship defines the interconnection between two entities. It is depicted as a diamond. There are two specific types of relationships:

  • Strong relationship - is depicted as a diamond with a normal line border.
  • Weak relationship (Identifying) - is depicted as a diamond with a double line border.

Strong Relationship

When entity A connected with a strong relationship to entity B, the existence of entity A is independent of the existence of entity B.

Relationship (ERD Chen)
Relationship (ERD Chen)

Weak Relationship

When entity A connected with a weak relationship to entity B, the existence of entity A depends on B entity existence.

Weak Relationship (Chen ERD)
Weak Relationship (Chen ERD)

Participation

The Chen ER diagram allows you to define a type of entity participating in a relationship, it can be:

  • Total participation - is depicted as a double line
  • Partial participation - is depicted as a solid line
  • Optional participation - is depicted as a dashed line

Cardinality

The relationship can connect one or multiple tuples from one entity to one or multiple tuples of another entity. You can use these cardinalities for the relationships:

  • One-to-one (1:1)
  • One-to-many (1:N)
  • Many-to-one (N:1)
  • Many-to-many (M:N)

Chen ER Diagram Tool

Chen ER diagrams can be created and edited with the ER diagram tool Software Ideas Modeler.

New Comment

Comment