Stores true/false values. When creating a boolean attribute the following validations and transformations are available to you:
Globally unique attributes must be unique among all the entities in the entity type. Locally unique attributes must be unique across all the plural attributes in a single entity (e.g., a single user profile).
The attribute must contain a non-null value.
Makes the attribute a primary key for the plural or entity type it exists in; this enables you to use API calls to target a specific record in a plural without knowing the actual identifier for that record. To set a primary key you also need the required constraint and either a unique or a locally-unique constraint.
Attributes that can be written to one time, then are never changed.