Create Sequence Diagrams: Use the flow you have identified (in step 4) at the Use Case and CRC level between objects and develop a set of sequence diagrams to represent the flow of control from a given actor(s) and its execution of the methods you have identified with your emerging model.

In the mine pump control system, the objects are:

Mine Pump

Water Sensor

Methane Sensor

Operator

Supervisor

Log

Alarm

You have been tasked to develop the architecture for a mine pump control system, designed to monitor and pump flood water out of mine shafts. As underground mining operations take place far below the water table, flooding into mine galleries and shafts is an ever-present danger. Excessive flooding is clearly a safety hazard for workers, but also has profitability implications ranging from equipment damage to productivity delays, to mine closures in extreme circumstances. The system to be developed will be required to monitor the water level in a given mine shaft using two sensors. A high water sensor that measures the maximum acceptable level of flooding in a shaft before pumping begins, and a low water sensor, which measures the minimum level of acceptable flooding and pumping stops. These sensors are used to start a mine pump. When the flooding level exceeds the level determined by the high water sensor the pump is switches on. When the water has been pumped out and the minimum level of acceptable flooding has been reached, as measured by the low water sensor, the pump switches off. In addition to flooding mining is often hindered by methane pockets, where gas seeps into the shafts and galleries triggering an evacuation. Again, this is a safety hazard, the mining staff wont be able to breathe, and even more critically, operating equipment may generate sparks which will cause the methane to ignite. Therefore, the system will include a methane sensor that will be used to trigger an evacuation alarm in the presence of dangerous levels of methane (measured in N parts per million), and also switch off the pump regardless of the current water level. The system is used by two key roles. The first is the Operator. This role is required to log in to the system with a username and password. Following a successful login, the operator is able to start or stop the pump if, and only if, the water level is between the high and low sensor limits. The second role is the Supervisor. A supervisor must verify their security credential as per the operator above. Following a successful login, they are able to switch the pump on, or off at any time. For example, a supervisor could run the pump after the flood level has dropped below the level set by the low water sensor. They could also switch the pump off if the water level goes over the maximum high level of flooding. In these cases, the supervisors actions override the automatic behavior of the pump. A supervisor is required to reset the pump system in order to re-establish automatic behavior. Finally, to meet Federal monitoring standards a persistent log is required to capture the following events: Pump switched on by high water sensor Pump switched off by low water sensor Pump switched on or off by operator or supervisor

Evacuation alarm triggered by methane sensor The reading of the methane sensor every 30 minutes The reading of the methane sensor (for the last 24 hours) can be read by the operator. All readings (up to 30 days) can be read by the supervisor. The supervisor also has the capability to add a note to any specific log event that occurs within 24 hours.