A concrete example is the categorisation of behavioural factors. Most public health experts would agree that as a determinant of health these contribute to health risk and/or protection; however some see behavioural factors as exclusively personal, while others see them as exclusively socio-economic, and some see them as both. Using an ontology, they can be classed under both categories, so that those who expect to find them under personal factors will do so, as will those who expect to find them under socioeconomic factors, as illustrated in Figure 12 . Thus all are satisfied (have found the category where they expected to), a practical result has been achieved, and an indecisive argument about where it is 'rightly' to be found has been avoided.