<!doctype html public «-//w3c//dtd html 4.0 transitional//en»> http-equiv=content-type> In recent years several investigations have been devoted to the study of large classes of (mainly degenerate) initial-boundary value evolution problems in connection with the possibility to obtain a constructive approximation of the associated positive C_0-semigroups.
In this research monograph we present the main lines of a theory which finds its root in the above-mentioned research field.
