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CIS339 EOC Questions - Chapter 10

CIS339 EOC Questions - Chapter 10 - EOC Questions Chapter...

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EOC Questions Chapter 10 Systems Analysis and Design with UML Version 2.0 Chapter 10 CLASS AND METHOD DESIGN 1. What are the basic characteristics of object-oriented systems? The basic characteristics of object-oriented systems are: Classes, objects, methods, and messages. The object is a basic unit that operates in the object-oriented world. Objects are created from classes which act as templates; they contain the ability to take action in the form of methods and they send and receive messages to and from other objects. Encapsulation: Objects are encapsulated so that they share only the elements that are relevant to other objects and hide their own data stores and methods when not relevant to other elements. Polymorphism allows an object to send the same message to a variety of objects, which may interpret and take action differently on the same message based on differences in their own logic. Inheritance allows developers to define classes that are related through common elements but that differ in other substantial ways. This makes it simpler to define classes. 2. What is dynamic binding? Dynamic binding refers to the ability of an object-oriented system to defer the data typing of objects until run time. This would allow a message such as compute employee pay to be interpreted differently at run time by 'salaried employee" and "hourly employee" objects. This feature is language dependent and must be implemented differently depending on the language in which the system is to be programmed. 3. Define polymorphism. Give one example of a "good" use of polymorphism and one example of a "bad" use of polymorphism. Polymorphism means having the ability to take on multiple forms. It is used in the object oriented world to refer to the ability for a message to be sent to different objects that will process it in different ways. An example of good polymorphism would be sending the message "print document" to a 'laser printer" or an "ink-jet" printer and having each printer perform its own operations to enact printing the document. An example of "bad" polymorphism would be "create order" which would mean start the sales process in a marketing system but might mean straighten up the living room in a housekeeping system. Page 1
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EOC Questions Chapter 10 4. What is inheritance conflict? How does an inheritance conflict affect the design? Inheritance conflict occurs when the name of an attribute or method of a class has the same as an attribute or method of a superclass. It creates complexity in updates since changes in the attributes or methods at one level will affect those at another level. 5. Why is cancellation of methods a bad thing? The purpose of the inheritance and classification of the classes and subclasses is to streamline and clarify the genuine underlying relationship amongst them. When an inherited method is cancelled, it indicates that some design flaw has been patched.
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