原文第2章第2节
数据抽象(Data Abstraction)
The general technique of isolating the parts of a program that deal with how data are represented from the parts that deal with how data are manipulated is a powerful design methodology called data abstraction.
分离数据的形式和处理过程。
抽象隔离(Abstraction Barriers)
An abstraction barrier violation occurs whenever a part of the program that can use a higher level function instead uses a function in a lower level.
当函数运行时，本应调用高级别子函数却使用低级别子函数时，即遇到抽象隔离。
