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Entity Relationship Diagram

The mermaid documentation describes Entity Relationship Diagrams as:

An entity–relationship model (or ER model) describes interrelated things of interest in a specific domain of knowledge. A basic ER model is composed of entity types (which classify the things of interest) and specifies relationships that can exist between entities (instances of those entity types). Wikipedia.

In Siren, we attempt to use the language of mermaid.js as consitently as possible for building up your Entity Relationship Diagrams.

For example:

$diagram = Siren::erd('Entity Relationship Diagram')
    ->addEntity($a = Entity::make('Entity A'))
    ->addEntity($b = Entity::make('Entity B')
        ->addAttribute(Attribute::make('id', 'string')
            ->comment('The identifier of ModelB')
            ->key(Key::PRIMARY)
        )->addAttribute(Attribute::make('age', 'int'))
    )
    ->addEntity($c = Entity::make('Entity C')
        ->addAttribute(Attribute::make('city', 'place'))
    )->addEntity($d = Entity::make('Entity D')
        ->addAttribute(Attribute::make('latlng', 'coordinates'))
    )->addEntity($e = Entity::make('Entity E'))
    ->addRelation(Relation::make('A to B', $a, $b)
        ->cardinality($a, Cardinality::ZERO_OR_ONE)
        ->cardinality($b, Cardinality::ZERO_OR_ONE))
    ->addRelation(Relation::make('A to C', $a, $c)
        ->cardinality($a, Cardinality::ZERO_OR_MORE)
        ->cardinality($c, Cardinality::ZERO_OR_MORE))
    ->addRelation(Relation::make('A to D', $a, $d)
        ->cardinality($a, Cardinality::ONE_OR_MORE)
        ->cardinality($d, Cardinality::ONE_OR_MORE)
        ->identifying())
    ->addRelation(Relation::make('A to E', $a, $e)->nonIdentifying());
---
title: Entity Relationship Diagram
---
erDiagram
"Entity A"
"Entity B" {
string id PK "The identifier of ModelB"
int age
}
"Entity C" {
place city
}
"Entity D" {
coordinates latlng
}
"Entity E"
"Entity A" |o--o| "Entity B" : "A to B"
"Entity A" }o--o{ "Entity C" : "A to C"
"Entity A" }|--|{ "Entity D" : "A to D"
"Entity A" ||..|| "Entity E" : "A to E"

 

 

Contents

 

 

Entity

Class: Plank\Siren\Builders\EntityRelationshipDiagram\Entity

Entitys are the way we classify the things of interest in the domain.

Entity::make('Entity');
erDiagram
"Entity"

 

Attribute

Class: Plank\Siren\Builders\EntityRelationshipDiagram\Attribute

Attributes are characteristics or properties of an Entity. They are used to describe the different features and characteristics of an Entity. When representing relational table structures, the attributes will often include the keys and indexes of the Entity.

You can also provide extra context to your Attributes by providing a comment using the comment(string $comment) method.

Entity::make('Comment')
    ->addAttribute(Attribute::make('title', 'string')->comment('The title of the Comment'))
    ->addAttribute(Attribute::make('body', 'text'));
erDiagram
"Comment" {
string title "The title of the Comment"
text body
}

 

Key

Enum: Plank\Siren\Builders\EntityRelationshipDiagram\Enums\Key

Key
PRIMARY
FOREIGN

When representing relational table structures, you can define if an Attribute is a foreign or primary key.

Entity::make('Comment')
    ->addAttribute(Attribute::make('post_id', 'uuid')
        ->comment('Id of the Post the comment belongs to')
        ->key(Key::FOREIGN))
    ->addAttribute(Attribute::make('user_id', 'uuid')
        ->comment('Id of the User who wrote the comment')
        ->key(Key::FOREIGN))
    ->addAttribute(Attribute::make('title', 'string'))
    ->addAttribute(Attribute::make('body', 'text'));
erDiagram
"Comment" {
uuid post_id FK "Id of the Post the comment belongs to"
uuid user_id FK "Id of the Post the comment belongs to"
string title
text body
}

 

 

Relation

Class: Plank\Siren\Builders\EntityRelationshipDiagram\Relation

A Relation is the association or connection of two Entitys.

$diagram = Siren::erd()
    ->addEntity($a = Entity::make('Entity A'))
    ->addEntity($b = Entity::make('Entity B'))
    ->addRelation(Relation::make('Related', $a, $b));
erDiagram
"Entity A"
"Entity B"
"Entity A" ||--|| "Entity B" : "Related"

 

Cardinality

Enum: Plank\Siren\Builders\EntityRelationshipDiagram\Enums\Cardinality

Cardinality
ZERO_OR_ONE
ZERO_OR_MORE
ONE_OR_MORE
ONLY_ONE

Cardinality describes the number of instances of one Entity that can be associated with another Entity.

$diagram = Siren::erd()
    ->addEntity($a = Entity::make('Entity A'))
    ->addEntity($b = Entity::make('Entity B'))
    ->addEntity($c = Entity::make('Entity C'))
    ->addEntity($d = Entity::make('Entity D'))
    ->addRelation(Relation::make('A to B', $a, $b)->cardinality($b, Cardinality::ONE_OR_MORE))
    ->addRelation(Relation::make('B to C', $b, $c)->cardinality($c, Cardinality::ONLY_ONE))
    ->addRelation(Relation::make('C to D', $c, $d)->cardinality($d, Cardinality::ZERO_OR_MORE))
    ->addRelation(Relation::make('D to A', $d, $a)->cardinality($a, Cardinality::ZERO_OR_ONE));
erDiagram
"Entity A"
"Entity B"
"Entity C"
"Entity D"
"Entity A" ||--|{ "Entity B" : "A to B"
"Entity B" ||--|| "Entity C" : "B to C"
"Entity C" ||--o{ "Entity D" : "C to D"
"Entity D" ||--o| "Entity A" : "D to A"

 

Identification

Enum: Plank\Siren\Builders\EntityRelationshipDiagram\Enums\Identification

Identification
NON_IDENTIFYING
IDENTIFYING

Identification describes the type of relationship between Entitys, where the existence of one entity depends on the existence of another entity. In an identifying relationship, one Entity is uniquely identified by the other Entity, which means that the first Entity cannot exist without the second Entity.

$diagram = Siren::erd()
    ->addEntity($a = Entity::make('Entity A'))
    ->addEntity($b = Entity::make('Entity B'))
    ->addEntity($c = Entity::make('Entity C'))
    ->addRelation(Relation::make('A to B', $a, $b))
    ->addRelation(Relation::make('B to C', $b, $c)->identification(Identification::IDENTIFYING))
    ->addRelation(Relation::make('C to A', $c, $a)->identification(Identification::NON_IDENTIFYING));
erDiagram
"Entity A"
"Entity B"
"Entity C"
"Entity A" ||--|| "Entity B" : "A to B"
"Entity B" ||--|| "Entity C" : "B to C"
"Entity C" ||..|| "Entity A" : "C to A"