It is often useful to think in terms of a hierarchy or spectrum of objectives for preventive activity, aimed at different points on the causal pathway, and for which there is often an important time dimension. For example, the short term aim of a preventive intervention at a certain point in time may be to change beliefs in the community about the risks of smoking; the intermediate objective may be to reduce uptake of smoking and smoking prevalence and the long term goal a reduction in rates of coronary heart disease and lung cancer. (Straton & Sindall 2001 : 1)