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Railway Coordination System A railway company requires an application to support dispatchers in organizing the setup and cancellation of train routes and the blocking of parts of a railway network (e.g., for maintenance) whilst enforcing safety rules. An example of such a safety rule is: "At most one train can occupy a given route." The railway network consists of a set of locations (track segments). The system shall identify each track segment by a sequential integer number. Each location has an occupancy detector and may also have an associated signal and/or switch (see Figure). Each switch may either be in the normal (straight through) position or reverse (directing the train to the side) position, or in neither position. A train can only travel over a switch if it is in either the normal or the reverse position. Each switch has sensors to detect its position, and a motor to change its position. Each signal may be set to clear (allowing for full speed), half (allowing reduced speed), or to stop. The network is divided into routes, which consist of a sequence of adjacent track locations extending from a location containing a signal, the lead signal of the route, to a location immediately before the next signal in the same direction. The lead signal of a route is actually in the route. Figure 1 has four routes labelled , T2, 3, r4. The system must be adaptable for use with different track layouts of varying complexity with multiple switches, signals, and routes, sigz sigi 10 12 Figure 1: Sample track layout for the Railway Coordination System. The system shall allow dispatchers to issue commands of the form md locn, where locn is the number of the location for which the command is intended, and cmd may be one of the following: sigelr set the s sighlf set the signal to half sigstp set the signal to stop sigblk block the signal sigubk unblock the signal sure set the switch to reverse swnor set the switch to normal stwblk block the switch swubk unblock the switch tkblk block the track segment tkubk unblock the track segment Railway Coordination System A railway company requires an application to support dispatchers in organizing the setup and cancellation of train routes and the blocking of parts of a railway network (e.g., for maintenance) whilst enforcing safety rules. An example of such a safety rule is: "At most one train can occupy a given route." The railway network consists of a set of locations (track segments). The system shall identify each track segment by a sequential integer number. Each location has an occupancy detector and may also have an associated signal and/or switch (see Figure). Each switch may either be in the normal (straight through) position or reverse (directing the train to the side) position, or in neither position. A train can only travel over a switch if it is in either the normal or the reverse position. Each switch has sensors to detect its position, and a motor to change its position. Each signal may be set to clear (allowing for full speed), half (allowing reduced speed), or to stop. The network is divided into routes, which consist of a sequence of adjacent track locations extending from a location containing a signal, the lead signal of the route, to a location immediately before the next signal in the same direction. The lead signal of a route is actually in the route. Figure 1 has four routes labelled , T2, 3, r4. The system must be adaptable for use with different track layouts of varying complexity with multiple switches, signals, and routes, sigz sigi 10 12 Figure 1: Sample track layout for the Railway Coordination System. The system shall allow dispatchers to issue commands of the form md locn, where locn is the number of the location for which the command is intended, and cmd may be one of the following: sigelr set the s sighlf set the signal to half sigstp set the signal to stop sigblk block the signal sigubk unblock the signal sure set the switch to reverse swnor set the switch to normal stwblk block the switch swubk unblock the switch tkblk block the track segment tkubk unblock the track segment
