The project involved extensive discussion and work regarding how to define the practice of public health, the methods and strategies used in public health interventions, and the bodies of knowledge that these draw on. There were two strong perspectives on what should be included in a classification. One perspective was restrictive and would narrow the scope of a 'methods' class to those methods that are peculiar to -or only used by -public health (e.g. population-based epidemiology, health promotion, environmental risk assessment). The other focus was on capturing all methods used by public health, including those that, while not specific to it, are employed by public health workers in the normal course of their work (e.g. administration, management, policy development).