In this work we will try to describe networkflows with methods of relational algebra. For this purpose we have a long way before us: first we deal with relations in classical sense, where our special attention is on the cardinality of relations under composition and meet (Dedekind inequality). After that we take a look at the so-called fuzzyrelations, which are "weighted" relations, where a number between zero and one is a measure for the weight of a pair. If on these constructions composition and operations on sets like meet and join are defined in a suitable way the laws for classic relations remain unchanged. Another important role will be played by semirings, by which we can prove properties of fuzzyrelations in an elegant manner.