Process isolation is where each process has its own distinct address space for its application code and data. In this way, it is possible to prevent each process from accessing another process' data. This prevents data leakage, or modification to the data while it is in memory.
Memory segmentation is a virtual memory management mechanism. The reference monitor is an abstract machine that mediates all accesses to objects by subjects. Data hiding, also known as information hiding, is a mechanism that makes information available at one processing level is not available at another level.