Moreover, using “controlled vocabulary” can help ensure consistent data compilation and facilitate analysis. Controlled vocabulary means that the monitor uses a list of terms or descriptors that is as exhaustive and mutually exclusive as possible, where preferred terms are used by those collecting data and analyzing the information. Advance planning can ensure a relatively comprehensive and controlled use of that information. It can, conversely, prevent overly narrow or rigid approaches, enabling NHRIs to judge the scale of the problem. For example, the Standard Minimum Rules for the Treatment of Prisoners require, in normal circumstances, that there should be only one person to a cell or room. A tool that records only whether that standard is met will not gather important data on the scale and severity of any over crowding or assess if it is more severe in some regions than in others or in some types of places of detention.