Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Assignment 1 Reactive Systems

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Reactive Systems  Traffic Lights  Scoreboard  Home Management System

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Traffic Light Controller (TLC): Brief Description  This is a system that handles traffic. It makes sure that cars only enter the intersection in an orderly manner. This is a safety precaustion which is designed to avoid accidents, and direct traffic.

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 TLC: Subject Domain  Physical Entities  Vehicles  Lights  Timer  Conceptual Entities  Traffic rules e.g. color rules  Lexical Entities

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 TLC: Connection Domain  Lights  Sensors

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 TLC: Cause and Effect Chain (1)  Condition  Traffic light is red  Event  Car rolls over sensor  Stimuli  The system registers the event  Response  The controller sends a green signal to the light.  Action  The light changes to green

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 TLC: Cause and Effect Chain(2)  Event  Timer signals light change  Stimuli  The system registers the signal  Response  System sends signal to light  Action  Light change

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 TLC: Cause and Effect Chain(3)  Event  The sensor malfunctions  Stimuli  The systems registers the error  Response  The system disregards the sensor  Action  Only the timer is used for traffic control

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 TLC: Requirements  The system must accept sensor and timer signals  The system must be programmable of authorized personnel  The system must only allow green light one way at the time

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 TLC: Constraints  The system can not detect the speed of approaching vehicles

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Scoreboard: Brief Description  A scoreboard is a large board for publicly displaying the score in a game or match. In many sports a scoreboard is used for keeping score, measuring time, and displaying statistics.

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Scoreboard: Subject Domain  Physical Entities  People  Conceptual Entities  Score  Time  Type of sport  Lexical Entities  None

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Scoreboard: Connection Domain  Control box

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Scoreboard: Cause and Effect Chain (1)  Event  Goal scored by Nicklas Bendtner  Effects that may happen anyway  Bendtner does a silly dance and the crowd goes wild  Stimuli  A person presses the score increment button on the control box  Response  The scoreboard controller sends a signal to the board  Action  The score is updated on the scoreboard

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Scoreboard: Cause and Effect Chain (2)  Event  2 min suspension of Anja Andersen  Effects that may happen anyway  The team walks out  Stimuli  A person registers a 2 min suspension  Response  The scoreboard controller sends a signal to the scoreboard  Action  A 2 min countdown is shown on the scoreboard

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Scoreboard: Cause and Effect Chain (3)  Event  2 min suspension is up  Stimuli  Timer sends a signal to indicate end of suspension  Response  Countdown is turned off on the scoreboard  Action  A player is allowed to enter the court

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Scoreboard: Requirements  A timer function  Handle different time intervals  Handle >= 3 digit scores  Handle several suspensions  …

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Scoreboard: Constraints  Correct operation from an operator  Cannot detect events

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 HMS: Brief Description  The Home Management System (HMS) is a system to control the electrical appliances of your home via the Internet. E.g. you can turn your appliances on/off and organize your appliances in groups.

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 HMS: Subject Domain  Physical Entities  Electrical appliances  Sensors, e.g. thermometer  Conceptual Entities  Temperature  Power consumption  Lexical Entities

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 HMS: Connection Domain  AMR (Automatic Meter Reader)  Switch

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 HMS: Cause and Effect Chain (1)  Condition  Temperature falls below 20°C in the living room  Stimuli  A thermometer sends a signal of the temperature to the system  Response  The system sends a message to a radiator in the room to turn on  Action  The radiator starts heating

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 HMS: Cause and Effect Chain (2)  Event  The father of the house wishes to find out last months power consumption  Stimuli  A request to see last months power consumption is received from a browser  Response  The system outputs the numbers to the browser  Action  The father prints the numbers

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 HMS: Cause and Effect Chain (3)  Event  New units a set up in the house  Stimuli  The new unit sends a message of its arrival to the system  Response  The system registers the unit in the system and adds it as an unregistered unit  Action  The father of the house renames the unit and adds it to the livingroom

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 HMS: Requirements  The system must handle many appliances and sensors  The system must support grouping of units  The system must be able to receive input via the Internet ...

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 HMS: Constraints  The system doesn’t know the exact location of the units  The system relies on the sensors to work properly  The system cannot detect potentially dangerous situations  Can only handle units with a zigbee attached

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Exercise We choose the Scoreboard system. The system displays the following characteristics of a reactive system (cf. [Wieringa, Fig. 1.1]):  Highly interactive: Yes, it is possible to input information to the scoreboard controller using the control box and see the result on the board.  Nonterminating process: Yes, the scoreboard is running all the time when turned on.  Interrupt-driven: Yes, e.g. the game time can be stopped at all times  State-dependent response: Yes, e.g. the system has different game modes for point management depending on the state

Morten Bohøj, Jakob Dam og Brian Jensen Gruppe 2 A A R H U S U N I V E R S I T E T SoITS d. 5 september 2006 Exercise  Environment-oriented response : Yes, e.g. the controller of the scoreboard sounds a buzzer indicating to the environment that the game is over.  Parallel processes: Yes, timers do not depend on each other and can be executed in parallel, e.g. game time and timers for suspension  Stringent real-time requirements: Yes, e.g. the scoreboard is expected to show immediately when a suspension runs out.