@startuml
class User {
    +id: int
    ...
}

class Role {
    +id: int
    name: string
}

class Permission {
    +id: int
    name: string
}

User "1" --> "N" Role
Role "1" --> "N" Permission

class User_Role_Permission {
    +user_id: int
    +role_id: int
    +permission_id: int
}

User_Role_Permission "N" --> "1" User
User_Role_Permission "N" --> "1" Role
User_Role_Permission "N" --> "1" Permission

class Role_Permission {
    +role_id: int
    +permission_id: int
}

Role_Permission "N" --> "1" Role
Role_Permission "N" --> "1" Permission
@enduml