RegisterPrinter is called by each worker in order to register itself as available.

RegisterWorker is called by each worker in order to register itself as available.

RemoveWorker is called in case any worker needs to make itself unavailable ( due to unrecoverable errors ).

AvailablePrinters is the global variable that contains all the workers printers that have registered themselves as available.

AvailableWorkers is the global variable that contains all the workers that have registered themselves as available.

Info represents the information that every worker gives about itself at the time of registration.

Input holds all the info that is given as input to each scanner.

Result contains all the info each worker can provide as a result, through the result channel, to the caller.

Worker is the interface that is used to provide transparent running of any type of worker from the main application.