Documenting Implementation

Question 1

What is an abstract class?

Answer 1

Class so general cant create direct instance of it

• contains common attriutes & sevices shared by concrete subclasses
• typically has abstract operations that cant be described

Question 2

What is an interface?

Answer 2

Abstract class that has only abstract operations; no attributes
(may have class constants)

Question 3

What is meant in UML when a class name is:
italic?
underlined?
normal?

Answer 3

italic; abstract class
underline; specific instance
normal; concrete class

Question 4

Describe 3 different kinds of generalisation

Answer 4

normal; relates specific class to general class
abstract class; superclass is abstract
realisation; relates concrete class to abstract interace

Question 5

Describe 4 different kinds of association

Answer 5

+normal; undirected conceptual relationship
+directed; structural relationship with sense of direction
+aggregation; whole/parts relationship; parts coordianted by whole
+composition; whole/parts exclusive relationship; parts owned by whole

Question 6

Describe 4 different kinds of navigation

Answer 6

+undirected; says nothing about navigation
+navigable; may navigate in direction; says nothing about reverse
+non-navigable; may not travel in direction; says nothing about reverse
+directed; one way navigation

Question 7

Describe 3 different kinds of end-role ownership

Answer 7

Default; association owns both end-roles-
One owner; x owns reference to y
Strongly-coupled; both classes own reference to each other

Question 8

Describe 3 styles of association

Answer 8

Standard; wth end roles & multiplicities
Named; helps reading of association (not for navigation)
Class; stores extra attributes belonging to association as a whole

Question 9

What is encapsulation?

Answer 9

fundamental principle fo object-oriented programming:

• information hiding
• modular protection

Question 10

What UML symbol is used to indicate the visibility of a class is:
public? private? protected? package?

Answer 10

+ public
- private
# protected
~ package

Question 11

What is the default visibilty of a package?

Answer 11

public

Question 12

what is the difference between import and access?

Answer 12

import; imported thing is treated as public

access; accessed thing is treated as private

Question 13

What is the difference between a class, an object and a role?

Answer 13

Class: models required structure and behaviour
Object; models a specifici occurence of data during an execution; an instance of a class
Role; models a typical object/refernce to an object

Question 14

What is a UML sequence diagram used for?

Answer 14

Illustrates flow of messages between object roles (rather than specific instances)
while a method is being executed, role has focus of control

Question 15

IN a UML sequence diagram; what is the difference between using a filled arrowhead and an open arrowhead with a dashed shaft?

Answer 15

Filled for method

open for constructor

Question 16

What is a synchronous flow?

Answer 16

Every call has to wait to be returned until the next thing happens

Question 17

What is the difference in arrows for synchronous and asynchronous flows?

Answer 17

sync: filled arrowhead
async: open arrowhead