This interface pattern is used for master data object type business objects (BOs). To change or read data, you do not normally access the master data objects with a large operation. SAP recommends that you group the data into meaningful categories and model an operation for each group (this is shown as either <part A> or <part B> in the interface pattern).
Interface Pattern for Master Data Object Type BOs
The Change <BO> <part> operation overwrites the data of a BO without checking whether any changes have been made to the data since the last read-only access. The Update <BO> <part> operation checks this.