Object Oriented Methodology

Question 1

Classes

Answer 1

Key abstractions of the system that define the attributes and behaviour of system objects, along with their relationships and interactions.

Question 2

Objects

Answer 2

Instances of classes that exist during execution of the software

Question 3

Classes -
Benefits

Answer 3

• Allows us to describe complex systems through meaningful abstractions
• Support difficult level views of the system including conceptual and implementation levels
• Allow all project members to have a shared understanding of the system

Question 4

Encapsulation

Answer 4

Mechanism for defining the functionality necessary for objects to be used and hiding details of how this is implemented

Question 5

Abstractions

Answer 5

Generalizations that define key characteristics and behaviour of objects

Question 6

Inheritance

Answer 6

Relationship between classes where one (the subclass) extends the data and behaviour of another (the superclass)

Question 7

Polymorphism

Answer 7

Mechanism for treating similar objects in the same way, and allowing the same action to possibly be performed in different ways.

Question 8

Encapsulation - Benefits

Answer 8

• Allows to minimize the effect of changing certain parts of the system on the overall system (extendibility of the system)

Question 9

Decorator

Answer 9

• A ‘Decorator’ pattern provides a way of adding optional functionality (“decoration”) to all classes in a hierarchy without changing the code for either the base class or any of the subclasses.
• Using this pattern, multiple decorators can be applied to an object (e.g. attaching a picture frame and scrollbars to a picture in the drawing editor). If there are several different kinds of decoration, we want to be able to use, we can derive multiple classes from the Decorator class to handle these separate kinds of added functionality.

Question 10

Class Diagram

Answer 10

A class diagram is a representation of the different classes that exist within a particular system, their properties and behaviour, interactions, and relationships. This diagram does not however describe the typical flow of operations, which can be summarized using a Sequence diagram.

Question 11

Refactoring

Answer 11

Rewriting, reworking, and re-architecting the software to make it easier to maintain, perform more robustly and/or faster without changing its external behaviour. Easier to maintain means the code is easier to read (understand) and adapt to new requirements (extensibility).

Question 12

Design Patterns -
Composite v Decorator

Answer 12

Although structurally somewhat similar, the intent is different. Composite allows to treat a composite (group of) leaves in the same way as a leaf. Decorator gives additional feature to a leaf and allows to treat “decorated” leaf in the same way as any other leaf.