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homotopy extension property


Let X be a topological spaceMathworldPlanetmath and A a subspaceMathworldPlanetmath of X. Suppose there is a continuous mapMathworldPlanetmath f:XY and a homotopy of maps F:A×IY. The inclusion map i:AX is said to have the homotopy extension property if there exists a continuous map F such that the following diagram commutes: