The foundation layers are shared by the subsystems, which provide the functionalities necessary to handle the Observation Blocks and Reduction Blocks during their life-cycle. A set of classes is of major importance in the Data Flow system. It includes in particular Templates, Observation Blocks, Frames, Reduction Recipes, and Reduction Blocks.
Templates define standard instrument operation modes and configurations.
The set of parameters associated to a Template is called the Template Signature. The detector acquisition system produces FITS files which are manipulated in the DFS in the form of Frames. Rules are applied on the incoming frames in order to create Reduction Blocks, which contain the set of frames to be processed and a reference to the applicable Reduction Recipe.