Public health practitioners expressed both broad and narrow views of what a classification system for public health should include. These views reflect the range of practical applications they identified (detailed in Section 3.1.3), and their underlying requirements. For instance, for health expenditure reporting, mutually exclusive activity categories at meaningful expenditure levels are required. From a health promotion viewpoint, the ability to model the public health business cycle, and to identify gross expenditure proportions for different elements (e.g. design, implementation, evaluation) are equally important.