Lecture 5: Centre for software reliability

Question 1

What are the design artifacts of a metamodel?

Answer 1

• Sybsystems are components that contain **UML elements **
• There is a <<trace>> </trace>relationship between two models

Question 2

What does a design model consists of?

Answer 2

1. Design subsystem
2. Design class
3. Interface
4. Use case realisation design
5. Deployment model

Question 3

What are design classes?

Answer 3

Captures the required behaviour of the system without worrying about the behaviour that is going to be implemented

Question 4

Where do design classes come from?

Answer 4

From analysis classes only

Question 5

What do design analysis classes model?

Answer 5

• The classes captures the problem domain
• The implementation details
• The attributes specified: type, visibility and default and values

Question 6

What must design classes have?

Answer 6

• Parameter lists
• Return types
• Visibility/exceptions
• SET & GET operations
• Constructors and destructors
• Complete set of attributes

Question 7

What are the characteristics of a Well- formed design classes?

Answer 7

• Complete and sufficient
• Doing something of what a user expects the class to do from its name
  Example: A BankAccount class provides: withdraw()/desposit() operations
• Primitive
• Should have a single primitive, never multiple ways of doing multiple things
• High Cohesion
  -** **Should have a set of operations that support the intent of the class
  Cohesion makes the class more understandable, small set of simple responsibilities such as HotelStay and not HotelCarStay
• Low Coupling
  -** **Should be associated with enough classes using semantic links

Question 8

What does the inheritance feature do in design classes?

Answer 8

Inheritance to **INHERITS **implementation

Question 9

What are the two things that must be considered in inheritance?

Answer 9

• *Interface**
• The public operations of base classes
• *Implementation**
  
  • The attributes, relationships, protected and private operations of the base classes

Question 10

What does the interface realisation do in the design classes?

Answer 10

Interface realisation in an interface has NO implementation but to DEFINE a contract

Question 11

Give an example from the tutorial of what a class diagram should look like:

Question 12

What does multiplicity model?

Answer 12

• Models a collection of things
• How many objects can participate in a relationship

Question 13

What 2 procedures does a design class involve?

Answer 13

Refining associations to aggregation or composition relationships

Question 14

What are the 6 associations of the relationships?

Answer 14

1. Implementing one-to-many associations
2. Implementing many-to-one associations
3. Implementing many-to-many associations- Stores a collection of objects from the source and target class
4. Implementing bidirectional associations – reify “make real” into design classes – Resolve from a bidirectional to a unidirectional
5. Implementing association classes – Refine all to association classes

Question 15

What must design classes also have?

Answer 15

• Navigability
• Multiplicity on both ends

Question 16

What is aggregation? Give an example

Answer 16

loose relationship with objects-

Example: Computer and its peripherals

Question 17

What is composition? Give an example

Answer 17

Strong type of relationship

Example: Tree and its leaves- Has ownership of its own parts

Question 18

What are the two main things aggregation consist of?

Answer 18

• Aggregation is a TRANSITIVE AND ASYMMETRIC relationship

Question 19

How is aggregation a model and composition shared in a diagram?

Answer 19

• Aggregation = shared between wholes
• Composition = shared between one and only one model

Question 20

Describe what the interaction diagrams contain and what it is

Answer 20

A collaboration of Design objects and classes that realise a use case

Contains:

• Design object interaction diagrams
• Links to class diagram