step 1                                                  
                                                                                                                                                                                                    
                                                                                                                                                                                                    
                                                                                                                                                                                                    
                                                                                                                                                                                                    
                                                                                                                                                                                                    
                                                                                                                                                                                                    
                                                                                                                                                                                                    
                                                                                                                                                                                                    
                                                                                                                                                                                                    
                      model 1                                                                                                                                                                       
                     repeat while () (100)                                                                                                                                                          
                     : sleep 5s                                                                                                                                                                     
                                                                                                                                                                                                    
                                                                                                                                                                                                    
                                                                                                                                                                                                    
                                                                                                                                                                                            infinite