Supplement the data query by two <viewCondition> elements in addition to the other conditions.
Set a condition for the obj_id attribute of the main object type with the compare type NOTIN. currentObjectType.id and currentAttributeType.id again refer to the list attribute and its object types. The second condition filters the client_sign attribute. currentObjectType.id receives the same value as before, currentAttributeType.id receives the value client_sign.