GIS Dictionary

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  1. [data models] An association in which the lifetime of the whole controls the lifetime of the parts. In a composition, the instances of two classes depend on each other; the whole controls the location and lifetime of its parts. For example, a digital map is composed of layers. When you move the map, the layers also move, and if you delete the map, its layers get deleted; therefore, the lifetime of these objects depend on one another.
  2. [cartography] The variety and quantity of patch types without consideration of the spatial arrangement of patches within a landscape mosaic.