{
    "rules": {
        ".read": true, 
        "messages": {
          "$message": { 
            ".write": "auth.uid != null && auth.uid === newData.child('user').val()",
            ".validate": "newData.child('message').val() != ''"
          }
        },
        "users": {
          "$user": {
            ".write": "auth.uid === $user" 
          }
        }        
    }
}