The interface between the Data Flow system and the reduction environment will be based on the Reduction Recipe class, a medium- to high-level description of a reduction procedure to which a Signature is attached. The aim of Reduction Recipes can be for instance to perform a flat-field correction, extract a spectrum, determine a magnitude correction, or estimate a magnitude. Lower level operations like fitting a polynomial, subtracting images, a.s.o. are assumed to be provided by the underlying data analysis system. At the level of the Data Flow system it is expected that this description of the operations to be performed on the data will remain stable over long period of time, whereas the actual implementation may vary.