Indicators and Criteria: Sustainability indicators are quantifiable and measurable variables
that can be used to evaluate system performance with relation to its objectives. Since
sustainability concerns system behaviour over time, a sustainable system is one with a nonnegative
trend in these variables. Technology adds to sustainability if it adds to the slope of
the trend line. Because of its multidimensionality, a suite of indicators will be required to
make realistic assessments about sustainability. TABLE 1 provides an indicative list of such
indicators.