We will need to consider limited regions of the map of all possible system states. Such regions are called a domain. We will be always dealing with rectangular domains so a domain will be specified by its upper left and lower right corners. Each corner is specified by a pair of numbers enclosed in parentheses separated by a comma. For the upper left corner the first number is the lower limit on the horizontal extent of the domain (LoH), the second is the upper limit on the vertical extent of the domain (HiV) like this: (LoH, HiV). The lower right corner is (HiH, LoV). The whole domain is specified by (LoH, HiV)/(HiH, LoV).