* Constraints - An arbitrary filter used to limit the granted action(s) to a specific subset of objects
At a minimum, a permission assignment must specify one object type, one user or group, and one action. The specification of constraints is optional: A permission without any constraints specified will apply to all instances of the selected model(s).
## Actions
There are four core actions that can be permitted for each type of object within NetBox, roughly analogous to the CRUD convention (create, read, update, and delete):
In addition to these, permissions can also grant custom actions that may be required by a specific model or plugin. For example, the `napalm_read` permission on the device model allows a user to execute NAPALM queries on a device via NetBox's REST API. These can be specified when granting a permission in the "additional actions" field.
!!! note
Internally, all actions granted by a permission (both built-in and custom) are stored as strings in an array field named `actions`.
Constraints are expressed as a JSON object representing a [Django query filter](https://docs.djangoproject.com/en/stable/ref/models/querysets/#field-lookups). This is the same syntax that you would pass to the QuerySet `filter()` method when performing a query using the Django ORM. As with query filters, double underscores can be used to traverse related objects or invoke lookup expressions. Some example queries and their corresponding definitions are shown below.
All constraints defined on a permission are applied with a logical AND. For example, suppose you assign a permission for the site model with the following constraints.
The permission will grant access only to sites which have a status of "active" **and** which are assigned to the "Americas" region. To achieve a logical OR with a different set of constraints, simply create another permission assignment for the same model and user/group.