How to set up relationship multiplicities

Multiplicities show how many instances of each end can participate in a relationship — like cardinality in data modelling.

Enable multiplicities on a relationship type

Select the M2 relationship type
In the Properties panel, find the Notation section
Enable Show Multiplicities

When enabled, edges of this relationship type display multiplicity labels at the source and target ends.

Set multiplicity values on M1 relationships

Select an M1 relationship instance (click the edge on a diagram or find it in the Explorer)
In the Properties panel, set:
- Source Multiplicity — e.g., “1”, “0..”, “1..”
- Target Multiplicity — e.g., “1”, “0..1”, “*”

Common multiplicity notations

Value	Meaning
`1`	Exactly one
`0..1`	Zero or one (optional)
`0..` or ``	Zero or more
`1..*`	One or more

Notes

Multiplicity display is controlled at the M2 level (on/off per relationship type)
Multiplicity values are set at the M1 level (per relationship instance)
If multiplicities are enabled but no value is set, the labels appear empty