These two systems, eight dimensions and a number of indicators mentioned above may be used as the core components in assessing tourism sustainability. It may not be necessary or possible to use all the indicators in all cases. Thus, it is important for a tourist destination to select a mostly appropriate group of dimensions and indicators for the assessment. Each dimension is composed of clusters of indicators in relation to tourism activities. The hierarchical structure of the indicators, dimensions, and systems is shown in Table 3. The table illustrates that to undertake a comprehensive assessment of the human system, such sub-systems of the human system as political, economic and socio-cultural aspects, and production structure should be evaluated. To assess the political sub-system, for example, a number of related indicators must be examined. To undertake a comprehensive assessment of the ecosystem, general environmental impacts, ecosystem quality, biodiversity and environmental management and policy as subsystems of the ecosystem need to be examined. To assess the general environmental impacts, for example, a number of indicators must be measured. In this process, a large range of specific aspects can potentially be assessed. As Hodge (1996) argues, an assessment hierarchy is a powerful tool. It provides a map of the assessment process, and serves to show explicitly what factors are, or are not, being considered in the assessment process. The assessment process builds from specific measures from bottom to top, drawing on the best available knowledge.