Notations

📖 Table of Contents

Changing the Notation
Overview of ER Notations
UML Notation

Changing the Notation

The notation can be changed in the header of .erd files:

erdiagram Example

notation = default // change the notation

entity A {}
entity B {}

relationship Rel {
   A[1] -> B[N] // specify cardinality and participation constraint
}

The currently supported notations are:

Default: default (used if the notation is not specified)
Bachman: bachman
Chen: chen
Crow's Foot: crowsfoot
UML: uml

Overview of ER Notations

Syntax	Description	Bachman	Chen	Crow's Foot
`[0..1]`	Zero or One
`[0..N]`	Zero or Many
`[1]` or `[1..1]`	One and only One
`[N]` or `[1..N]`	One or Many

UML Notation

UML is often used for data modeling and its concepts are similar to ER modeling with slight variations. In bigER, the UML notation has the following differences:

Binary relationships are rendered as direct connections with no connecting diamond node
Visibility of attributes can be specified
Aggregation and Composition relationships can be specified

Binary- & Ternary Relationships

Binary without labels	Binary with labels

Ternary without labels	Ternary with labels

Visibility

The UML Notation allows specifying the visibility of attributes. The visibility is shown in the diagram, and it has no effect on the output of the generators.

Show Textual ER Model (click to open)

entity Example1 {
    + attr1: INT key
    - attr2: VARCHAR
    # attr3: VARCHAR
    ~ attr4: DATE
}

entity Example2 {
    public attr1: INT key
    private attr2: VARCHAR
    protected attr3: VARCHAR
    package attr4: DATE
}