Agenda 21 recommends that during the period 1993-2000, all countries should undertake projects in selected cities for the collection, analysis and subsequent dissemination of urban data, including environmental impact analysis, at the local, state/provincial, national and international levels, with the active participation of the business sector as appropriate, and the establishment of city data management capabilities. UN organizations such as Habitat, UNEP and UNDP could provide technical advice and model data management systems.