def get_schema():
    """Schema structure of this resource

    :return: schema dictionary
    :rtype: dict
    """
    return {'schema': {'schema_version': {'type': 'integer', 'default': 1},
        'imported_from': {'schema_version': 1, 'title': 'Imported from',
        'comment': 'Item importation source (alignak-backend-import, ...)',
        'type': 'string', 'default': 'unknown'}, 'definition_order': {
        'schema_version': 1, 'title': 'Definition order', 'comment':
        'Priority level if several elements have the same name', 'type':
        'integer', 'default': 100}, 'first_notification': {'schema_version':
        1, 'title': 'First notification count', 'comment':
        'Nagios legacy. Number of the first notification this escalation will be used. **Note** that this property will be deprecated in favor of the ``first_notification_time``.'
        , 'type': 'integer'}, 'last_notification': {'schema_version': 1,
        'title': 'Last notification count', 'comment':
        'Nagios legacy. Number of the last notification this escalation will not be used anymore. **Note** that this property will be deprecated in favor of the ``last_notification_time``.'
        , 'type': 'integer'}, 'name': {'schema_version': 1, 'title':
        'Service escalation name', 'comment':
        'Unique service escalation name', 'type': 'string', 'required': 
        True, 'empty': False, 'unique': True}, 'alias': {'schema_version': 
        1, 'title': 'Alias', 'comment':
        'Element friendly name used by the Web User Interface.', 'type':
        'string', 'default': ''}, 'notes': {'schema_version': 1, 'title':
        'Notes', 'comment':
        'Element notes. Free text to store element information.', 'type':
        'string', 'default': ''}, 'services': {'schema_version': 1, 'title':
        'Services', 'comment':
        'List of the services concerned by the escalation.', 'type': 'list',
        'schema': {'type': 'objectid', 'data_relation': {'resource':
        'service', 'embeddable': True}}}, 'hosts': {'schema_version': 1,
        'title': 'Hosts', 'comment':
        'List of the hosts concerned by the escalation.', 'type': 'list',
        'schema': {'type': 'objectid', 'data_relation': {'resource': 'host',
        'embeddable': True}}}, 'hostgroups': {'schema_version': 1, 'title':
        'Hosts groups', 'comment':
        'List of the hosts groups concerned by the escalation.', 'type':
        'list', 'schema': {'type': 'objectid', 'data_relation': {'resource':
        'hostgroup', 'embeddable': True}}}, 'first_notification_time': {
        'schema_version': 1, 'title': 'First notification time', 'comment':
        'Duration in minutes before sending the first escalated notification.',
        'type': 'integer', 'default': 60}, 'last_notification_time': {
        'schema_version': 1, 'title': 'Last notification time', 'comment':
        'Duration in minutes before sending the last escalated notification. Escalated notifications will be sent-out between the first_notification_time and last_notification_time period.'
        , 'type': 'integer', 'default': 240}, 'escalation_period': {
        'schema_version': 1, 'title': 'Escalation time period', 'comment':
        'No escalation notifications will be sent-out except during this time period.'
        , 'type': 'objectid', 'data_relation': {'resource': 'timeperiod',
        'embeddable': True}}, 'escalation_options': {'schema_version': 1,
        'title': 'Escalation options', 'comment':
        'List of the notifications types this escalation is concerned with. This escalation will be used only if the host is in one of the states specified in this property.'
        , 'type': 'list', 'default': ['w', 'c', 'x', 'r'], 'allowed': ['w',
        'c', 'x', 'r']}, 'notification_interval': {'schema_version': 1,
        'title': 'Notifications interval', 'comment':
        'Number of minutes to wait before re-sending the escalated notifications if the problem is still present. If you set this value to 0, only one notification will be sent out.'
        , 'type': 'integer', 'default': 60}, 'users': {'schema_version': 1,
        'title': 'Escalation users', 'comment':
        'List of the users concerned by this escalation.', 'type': 'list',
        'schema': {'type': 'objectid', 'data_relation': {'resource': 'user',
        'embeddable': True}}, 'required': True}, 'usergroups': {
        'schema_version': 1, 'title': 'Escalation users groups', 'comment':
        'List of the users groups concerned by this escalation.', 'type':
        'list', 'schema': {'type': 'objectid', 'data_relation': {'resource':
        'usergroup', 'embeddable': True}}, 'required': True}, '_realm': {
        'schema_version': 1, 'title': 'Realm', 'comment':
        'Realm this element belongs to.', 'type': 'objectid',
        'data_relation': {'resource': 'realm', 'embeddable': True},
        'required': True}, '_sub_realm': {'schema_version': 1, 'title':
        'Sub-realms', 'comment':
        'Is this element visible in the sub-realms of its realm?', 'type':
        'boolean', 'default': True}, '_users_read': {'schema_version': 1,
        'type': 'list', 'schema': {'type': 'objectid', 'data_relation': {
        'resource': 'user', 'embeddable': True}}}, '_users_update': {
        'schema_version': 1, 'type': 'list', 'schema': {'type': 'objectid',
        'data_relation': {'resource': 'user', 'embeddable': True}}},
        '_users_delete': {'schema_version': 1, 'type': 'list', 'schema': {
        'type': 'objectid', 'data_relation': {'resource': 'user',
        'embeddable': True}}}}, 'schema_deleted': {}}
