Edge Properties and Cardinality

Define relationship properties with typed attributes. Set cardinality (1:1, 1:N, N:1, N:M) to document relationship semantics. Add notes and configure edge direction.

February 5, 2026

Edges in graph diagrams can have properties, cardinality, and documentation just like nodes. In Graph DB mode, edge properties are included in Cypher export and represent attributes stored on Neo4j relationships.

Edge Attributes

Every edge supports these core attributes:

Attribute	Description	Required
Label	Relationship type name (e.g., PLACED, CONTAINS)	Optional
Source Label	Text displayed near the source node	Optional
Target Label	Text displayed near the target node	Optional
Cardinality	Relationship multiplicity (1:1, 1:N, N:1, N:M)	Optional
Directed	Whether the relationship has direction	Default: true
Properties	Typed attributes on the relationship	Optional
Note	Markdown documentation for the edge	Optional
Colour	Edge stroke colour	Optional

Cardinality

Cardinality indicates how many instances can participate in the relationship:

Cardinality	Meaning	Example
1:1	One-to-one	Person HAS_PASSPORT Passport
1:N	One-to-many	Customer PLACED Order
N:1	Many-to-one	OrderLine BELONGS_TO Order
N:M	Many-to-many	Student ENROLLED_IN Course

Setting Cardinality

Edge Properties

Relationships can have their own properties, just like nodes. This is useful for storing data about the relationship itself.

Adding Edge Properties

Edge Property Types

Edge properties support the same types as node properties:

Type	Use Case
string	Relationship metadata, codes, identifiers
int	Quantities, counts, sequence numbers
float	Prices, percentages, measurements
boolean	Flags, toggles, status indicators
date	Relationship start/end dates
datetime	Timestamps for relationship events
uuid	Relationship identifiers
json	Complex nested data on relationships

Direction

By default, edges are directed (have an arrow). You can make edges undirected for symmetric relationships.

Directed	Rendering	Use Case
true	Arrow points from source to target	PLACED, CONTAINS, FOLLOWS
false	No arrow, line only	FRIENDS_WITH, RELATED_TO, SIBLING_OF

Edge Labels

Edges support three label positions:

Customer ----[PLACED]----> Order
  owner                      item
(sourceLabel)            (targetLabel)

Edge Notes

Add documentation to edges using the Note field. Notes support Markdown formatting and appear in tooltips.

## PLACED Relationship

Represents a customer placing an order.

**Business Rules:**
- A customer can place multiple orders
- Each order belongs to exactly one customer
- The relationship stores the channel (web, mobile, phone)

Cypher Export

Edge properties and cardinality are included in Cypher export:

// Customer -[PLACED]-> Order (1:N)
// A customer places orders through various channels
MATCH (a:Customer {id: $customerId})
MATCH (b:Order {id: $orderId})
CREATE (a)-[:PLACED {
  date: $date,           // datetime, required
  channel: $channel,     // string, enum: [web,mobile,phone]
  promotionCode: $promotionCode  // string, nullable
}]->(b);

Validation

Edge validation in Graph DB mode checks:

Rule	Severity	Description
missing-cardinality	Warning	Edge has no cardinality defined
duplicate-property-name	Error	Same property name used multiple times on edge
missing-label	Info	Edge has no relationship type label

Edge Property Storage

Edge properties are stored in the diagram file:

{
  "id": "edge-001",
  "source": "node-customer",
  "target": "node-order",
  "label": "PLACED",
  "cardinality": "1:N",
  "directed": true,
  "properties": [
    {
      "id": "prop-001",
      "name": "date",
      "type": "datetime",
      "required": true
    },
    {
      "id": "prop-002",
      "name": "channel",
      "type": "string",
      "required": false
    }
  ],
  "note": "Customer places an order through a sales channel."
}