Fig. 4.

Dataset four-layer metamodel hierarchical architecture for dataset interoperability. Data at M0 level, such as subject demographics, are described by models at the M1 level, such as CDISC SDTM dataset format, which in turn are described by metamodels at the M2 interoperability level, such as subject dataset descriptor, which in turn conforms to a generic dataset descriptor model described in M3 layer.