Here we discuss granularity of the persistence of the muon digit container. Our container is a persistent object and in the model of Ma and Meesen it is stored as a collection of of digit subcontainers.
This in not neccessarily the same as the granularity with which our container provides access to users. That is driven by other considerations and is likely to be different. It is discussed in the later section describing the user interface.
The motivation for the Ma and Meesen subcontainers is to provide fast access to a subset of the data by not reading in unused data. This is most important for raw data and we assume the unpacking of raw data is done at the same level of granularity. The subcontainers are only created (or at least filled) when their data is requested.
There are many levels of granularity ranging from individual digits to the entire muon subsystem. We are interested in levels of granularity that match well with organization of data within the event. We find three candidates: readout crates (ROC's), readout drivers (ROD's) and technology.