9. Abstraction in OO Programs -- Packages and Name spaces The next level (level 2) of abstraction is found in some (but not all) OO languages. A package, Unit or Name Space allows a programmer to surround a collection of objects (a small community in itself) with a layer, and control visibility from outside the module.
10. Abstraction in OO Languages -- Clients and Servers The next level of abstraction considers the relationship between two individual objects. Typically one is providing a service, and the other is using the service.
11. Abstraction in OO languages -- Description of Services We can examine just the person providing a service, independent of the client. We define the nature of the services that are offered, but not how those services are realized. (like billboard advertisements)
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13. Levels of Abstraction -- An Implementation Next ( level 4 ) we look at the services provided, but from the implementation side: public class LinkedList implements Stack ... { public void pop () throws EmptyStackException { ... } ... } Concern here is with the high level approach to providing the designated service.
14. Levels of Abstraction -- A Method in Isolation Finally (level 5), we consider the implementation of each method in isolation. public class LinkedList implements Stack ... { ... public void pop () throws EmptyStackException { if (isEmpty()) throw new EmptyStackException(); removeFirst(); // delete first element of list } ... } Every level is important, and often you move quickly back and forth between levels.
38. Summery Looking at the history, we can separate it into three periods of time: The Function Centered View Assembly language Functions and Procedures Major concern is characterizing the functionality of an application The Data Centered View Modules Abstract Data Types Major concern is characterizing the data types used in an application The Service Centered View Object-Oriented Programming Major concern is characterizing the services provided by objects in the application
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41. Basic Idea of Cloud Computing Cloud computing is a paradigm of computing in which dynamically scalable and often virtualized resources are provided as a service over the Internet. Users need not have knowledge of, expertise in, or control over the technology infrastructure in the "cloud" that supports them.
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