The role class “StorageUnit” should be used defining the role based equipment hierarchy defined in IEC 62264-1:2013 at the storage unit level: The definition of an “StorageUnit” is given in IEC 62264-1: 2013, 5.3.9: “Storage zones and storage units are the lowest level of material movement equipment typically scheduled by the Level 4 and Level 3 functions for discrete, batch and continuous manufacturing processes. Storage units are typically managed at a finer level of detail than a storage zone. The physical location of a storage unit may change over time; for example, for goods in transit. Storage units may be dedicated to a given material, group of materials, or method of storage. Storage units can be further divided to address any hierarchical storage management scheme.”