A map (= continuous function) is of order ≤ k if each of its point-inverses has at most k elements. Following [4], maps of order ≤ 2 are called simple. Which maps are compositions of simple closed [open, clopen] maps? How many simple maps are really needed to represent a given map? It is proved herein that every closed map of order ≤ k defined on an n-dimensional metric space is a composition of (n+1)k-1 simple closed maps (with metric domains). This theorem fails to be true for non-metrizable spaces. An appropriate map on a Cantor cube of uncountable weight is described.
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Two equivalent definitions of the Cech-Lebesgue dimension are extended to closed (continuous) maps. This leads to two different dimension-like functions: the covering dimension and partition dimension of maps. A few characterizations of at most n-dimensional maps (for both dimensions) are proved as well as countable and locally finite sum theorems.
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