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Device: A representation of particular piece of hardware installed in the system. A device is installed by telling the user interface that it exists specifying its serial number and then powering it up the Add Device use case.
The software should then be able to detect its presence wirelessly. Cannot be changed. Unique for each device manufactured by SafeHome. May be left blank although this would make the system less informative and may be changed at any time. The label might, for example, describe symbolically the location of a sensor or camera.
Sensor: Represents a device that should trigger a reaction by the system if some condition becomes true a door is open, CO is detected, water is detected, motion is detected, fire is detected. There can be several subclasses. SafeHome Architectural Model. AlarmSignaler: Represents a device that will sound an alarm. Camera: Represents a camera that can send images to the system, and can be panned and zoomed.
Represents certain parameters set for that device in a particular configuration. These parameters are changed in the Change Device In Configuration use case. This can be used to divide the house into up to five zones e. The default is zero, meaning undefined zone. An AlarmSignaler in zone 0 will always sound. An AlarmSignaler given a numbered zone will only sound if a sensor in that zone triggers the alarm. This is discussed more later. The default is true. The homeowner may want to set this to false for some devices — e.
FloorPlan: Part of an optional feature of the system. The homeowner may set up several floor plans that can be looked at visually in the web interface — there would be one for each floor of the house.
These can be used, for example, to help him or her understand where a camera is pointing, etc. The floor plan has a set of devices each with its own FloorCoordinates and a set of Segments representing doors, walls, etc. Each appears differently visually when drawn in the user interface. FloorCoordinates: Specify the location in meters from the top-left corner of the FloorPlan although the homeowner does not have to draw the unit to scale if he or she does not want to.
Figure 6 is a simple activity diagram showing the top level behavior of the SafeHomeSystem class. When the SafeHome central processor is running, it must be able to do two things at once: Perform its main security monitoring functions and respond to configuration changes.
For example, the system could be armed and detecting burglars at the same time as the homeowner is logging in from some external location via the web to change the active configuration e. Figure 6: Top level activity diagram Figure 7 describes the behavior of the SafeHomeSystem class during the Monitoring activity of Figure 6. There are three possible values for its activationState attribute: CheckingSystem, Disarmed and Armed; the latter two are substates of NormalOperation — in which the system spends most of its time.
The system toggles backwards and forwards between Disarmed and Armed in response to user actions. Note that Figure 7 does not model the user interface — this is kept quite separate, as is good practice in software engineering and is discussed in the context of Figure 9. The successfulActivation and successfulDeactivation events are triggered by the user interface. This is the deep history symbol; it means that after resetting, the system will go back to doing what it was doing before i.
This is necessary to prevent the reset process from circumventing security. In this state the system has to respond to sensors by triggering alarms. Everything is normal while it is in this substate. If a motion detector detects motion, no alarm is immediately sounded: The system requires more than a short period of motion to sound an alarm; the motion could be caused by the homeowner coming home and going through the process of deactivating the system at a control panel. Or the motion could be caused by a minor earth tremor or a gust of wind.
However, the system does go into Motion Detector Triggered state since it needs to behave differently if the motion persists. After 45 seconds the system goes into Heightened Motion Sensitivity state. In this state, the system will respond immediately to any further motion; it will stay in this state for 5 minutes before dropping back to No Sensors Triggered state.
If any other sensor is triggered or if a motion sensor is triggered in Heightened Motion Sensitivity state, then the system goes into Acting On Alarm state. It starts the alarms sounding and calls the monitoring company. A timer is started on entry into this state, if no further sensors are triggered, this timer will time out after a user-configurable amount of time and the alarm will go off.
This prevents a persistent false alarm from ringing indefinitely. On the other hand, if sensors continue to be triggered, the timer is reset, so the alarm will keep ringing. Figure 8: State diagram of the Armed state Figure 9 shows the user interface of a model of control panel that is used to arm or disarm the system.
Note that other user interfaces could be developed — in particular, there may be a web based interface that would allow remote arming of the system, or an interface that could be controlled by the monitoring company. In the following we will only model the events and state transitions, not what is displayed on the screen.
The control panel starts up displaying a welcome message. Then it goes into Ready For Use state if the system is currently disarmed, or Security Delay 2 state if the system is currently armed. We will explain the purpose of Security Delay 2 a bit later.
Ready For Use state means that the system is not armed; in order to perform some function, however, the user must enter a valid ActivationCode. As soon as the first number key is pressed, the control panel goes into Entering Activation Code state. The panel stays in this state as long as the user keeps pressing number keys activation codes can be very long if the configuration manager wants.
When the user has finished entering his or her code he or she presses a function key: There are three function keys in the control panel modeled here: Arm — Stay, Arm — Away, and Test.
If the user presses Test, and the activation code was correct, then the system goes into Test Alarm state for five seconds before returning to Ready For Use state. If the user presses either Arm key after entering a valid code, the system goes into Delay To Leave state.
This gives the user time to leave the house, lock the doors, etc. If the user presses a function key without entering a valid activation code, the system goes into Security Delay 1 for a few seconds. The security delay prevents somebody with ill intent from trying out codes over and over again rapidly until they randomly stumble on a valid one; they always have to put up with a delay, which should make the random guessing process infeasible.
If a user presses the Cancel key while entering the activation code, the system goes back to Ready For Use state. This ensures that if a legitimate user starts typing the wrong code, they can try again immediately. Sixty seconds after entering Delay To Leave state, the system triggers the successfulActivation event and goes into Awaiting Disarm Activation Code state. Triggering this event forces the SafeHomeSystem to become armed, as indicated in Figure 7.
Note that it is possible for there to be more than one user interface in use another control panel, e. At any time if a different UI arms the system, a transition will always be made instantly to Awaiting Disarm Activation Code state — in other words, this would happen, even if the user of this control panel was in the middle of activating the system. Once the system is armed, the only way to disarm it is to enter a valid ActivationCode again.
As soon as the user presses the first number key, the system goes into Accepting Disarm Code state. The system keeps accepting keys until a valid code has been entered, at which time the UI triggers the successfulDeactivation event and transitions to Ready For Use state.
However it will not be possible to try again for 20 seconds due to the presence of the Security Delay 2 state. This prevents rapid retries by someone trying to guess the code. Starting up the control panel while the system is armed also incorporates this security delay to account for the situation where the user unplugs and plugs in the control panel to reset it. Thoughts about extensions to this model The model presented above could be extended and improved indefinitely.
We leave it as an exercise for the reader to make changes. The purpose of this document has been to present the top level architecture of the system, and to help you learn about modeling, rather than exhaustively model every detail of SafeHome. However, as pointed out at the beginning, we may update this document at some future time. For example, in Figures 8 and 9 there are several fixed delays built into the system.
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