2.1-Introduction-to-Data-Abstraction

2.1.1 Example: Arithmetic Operations for Rational Numbers

1. Data abstraction: isolate the use of data from its implementation details

2.1.2 Abstraction Barriers

1. Abstraction barriers: a mechanism for enforcing the separation between different levels ob abstraction.
2. Benefits of abstraction barriers: ability to change the implementation of a module without affecting its external users
3. Violation of abstraction barriers: access and manipulate the internal implementation of a module directly
4. Refactoring with abstraction barriers

2.1.3 What Is Meant by Data?

1. Data as a set of objects
2. Hierarchical structure of data: objects can contain other objects as components
3. Composite data objects: pairs, sequences, trees
4. Data and the interpreter: interpreter can be designed to recognize and manipulate different data types