def get_doc():
    """Get documentation of this resource

    :return: rst string
    :rtype: str
    """
    return """
    The ``realm`` model is used to represent a realm of the monitored system.

    The Alignak framework distributed architecture allows to have a unique Alignak instance to
    manage a huge system. I nsuch a cas, it is interesting to be able to cut this huge
    configuration into parts for different sites, customers, ... For Alignak, those parts are
    **realms**.

    A realm is a group of resources (hosts ) tha users will be able to manage. All resources in
    the Alignak backend are attached to a realm. At minimum, it is the *All* realm that always
    exist in any Alignak instance.

    The realm organization is hierarchical. A realm may have sub-realms that also may have
    sub-realms. Sub-realms visibility of the resources allow the Alignak backend users to view
    the resources defined in upper realms.
    """
