最病 Persistence from programming languages o Mechanisms for storing objects in files and retrieving them 口 Simple objects: a e.g. integers, characters a conventional methods usable 口 Composite objects: a contain references to other objects a Persistence Closure principle: Any storage and retrieval mechanism must handle the object and all its dependents >otherwise: dangling references Institute of Computer Software 2021/1/28 Nanjing UniversityPersistence from programming languages  Mechanisms for storing objects in files and retrieving them  Simple objects:  e.g. integers, characters  conventional methods usable  Composite objects:  contain references to other objects  Persistence Closure principle: ◼ Any storage and retrieval mechanism must handle the object and all its dependents. → otherwise: dangling references 2021/1/28 Institute of Computer Software Nanjing University 42