Week 5

Question 1

Why should requirements be analysed?

Answer 1

Use cases give little information about structure of software.

Some parts may already exist as standard components

Question 2

What does requirements analysis aim to identify?

Answer 2

Structure that can meet the requirements

Common elements that are only needed once

Pre-existing elements that can be reused

Interaction between requirements

Question 3

What does an analysis model do?

Answer 3

Confirm what the client wants the system to do

Be understandable and correctly detailed

Question 4

What is the main technique to analyse requirements?

Answer 4

Class diagram

Question 5

What two ways can a class diagram be produced?

Answer 5

Directly based on knowledge of application domain

By producing separate class diagram for each use case, and then combining them (analysis class model)

Question 6

What is realization?

Answer 6

Going from use case to working software implementation (and all the steps between)

Question 7

What is the communication diagram approach?

Answer 7

Analyse one use case at a time

Identify likely classes involved

Draw communication diagram that fulfils the needs of the use case

Translate into use case class diagram

Repeat for all use cases

Assemble all the diagrams into a single analysis class diagram

Question 8

What does robustness analysis aim to do?

Answer 8

Produce a set of classes robust enough to meet the requirements of a use case

Question 9

What assumptions does robustness analysis make?

Answer 9

A class or classes are needed to handle user interface

Logic of the use case is abstracted away from entity classes

Question 10

What are entity classes?

Answer 10

Classes that store persistent data

Question 11

What do boundary objects model?

Answer 11

Interaction between system and actors

Question 12

What do control objects do?

Answer 12

Co-ordinate and control other objects

Question 13

Boundary and Control classes are likely to be

a) unique to one application
b) reusable in multiple applications

Answer 13

a) unique to one application

Question 14

What are the three steps in realization of class diagrams?

Answer 14

1) Define entity objects
2) Add control objects
3) Add boundary objects

Question 15

What are 8 reasonability checks for candidate classes?

Answer 15

Is it beyond the scope of the system?

Does it refer to the system as a whole?

Does it duplicate another class?

Is it too vague?

Is it too tied up with physical inputs and outputs?

Is it really an attribute?

Is it really an operation?

Is it really an association?

Question 16

What is a collaboration?

Answer 16

A group of objects or classes that work together to provide an element of functionality or behaviour

Question 17

What is an interaction?

Answer 17

An interaction defines the message passing between lifelines (e.g. objects) within the context of a collaboration to achieve a particular behaviour

i.e. how the two objects interact to get something done

Question 18

What do sequence diagrams show?

Answer 18

Interaction between lifelines arranged in a time sequence

Question 19

What does a synchronous message cause to happen on the invoking operation?

Answer 19

Suspend execution until the synchronous operation is complete

Question 20

Synchronous messages are also known as

Answer 20

procedural calls

Question 21

What 3 techniques can be used to model complex interactions in sequence diagrams?

Answer 21

Interaction fragments

Lifelines for subsystem or groups of objects

Continuations

Question 22

what are interaction fragments and how are they used?

Answer 22

Separate sequence diagram for “sub sequences”

“ref” box on main sequence diagram with name of fragment