## PROPERTY_CONSTRAINT_SCHEMA

Examples of schema definitions that can be mixed or created as separate schemata and assigned to property.

### Must exists

```json
{
    "type": "PROPERTY_CONSTRAINT_SCHEMA",
    "constraints": {
        "must_exists": true
    },
    "tags": [
        "property constraint",
        "must exists"
    ]
}
```

### Single value

Properties such as `place of birth` or `maternity hospital` are prime examples where only a `single` value is expected to exists for a person entity.

```json
{
    "type": "PROPERTY_CONSTRAINT_SCHEMA",
    "constraints": {
        "single_value_constraint": true
    },
    "tags": [
        "property constraint",
        "single value"
    ]
}
```

### Non negative

```json
{
    "type": "PROPERTY_CONSTRAINT_SCHEMA",
    "constraints": {
        "non_negative_integer": true
    },
    "tags": [
        "property constraint",
        "integer",
        "number"
    ]
}
```

## CLASS_CONSTRAINT_SCHEMA

### Mandatory properties

```
{
    "type": "CLASS_CONSTRAINT_SCHEMA",
    "constraints": {
        "mandatory_properties": [
            "Gender",
            "Name",
            "Birthdate",
            "Birthplace"
        ]
    },
    "tags": [
        "class constraint"
    ]
}
```

### Shape constraint

```
{
    "type": "CLASS_CONSTRAINT_SCHEMA",
    "constraints": {
        "mandatory_properties": [
            "Gender",
            "Name",
            "Birthdate",
            "Birthplace"
        ],
        "shape_constraint": [
            {
                "property": "Gender",
                "max_cardinality": 1
            }
        ]
    },
    "tags": [
        "class constraint"
    ]
}
```

## See also

- [`property.constraint.md`](https://github.com/SemanticMediaWiki/SemanticMediaWiki/blob/master/src/Schema/docs/property.constraint.md)
- [`class.constraint.md`](https://github.com/SemanticMediaWiki/SemanticMediaWiki/blob/master/src/Schema/docs/class.constraint.md)