Build Models & Prototypes to Represent the Requirements (20%)

Question 1

Why do we model requirements?

Answer 1

• Clarify understanding
• Unambiguous communication
• Generating questions
• Cross checking for consistency & completeness (CRUD)
• Defining Business rules

Question 2

What is an example of a functional model?

Answer 2

Use case diagram

Question 3

What is a use case?

Answer 3

describe a piece of system functionality that delivers value to the actor
focuses on the ‘what’ not the ‘how’

Question 4

What naming convention is applied to use cases?

Answer 4

Verb noun i.e. make payment / cancel ticket

Question 5

Why are use cases useful?

Answer 5

Use Case Diagrams summarise functional requirements for the IT/Business system. They represent the user perspective and needs

Question 6

What are the levels in a use case diagram?

Answer 6

Rectangle - System boundary (part/whole)
Stick figures - System Actors (/user roles) interacting with the system (their goals)
Circles with verb noun - system functionality
Association - shows how the interaction between actors and the system

Question 7

Examples of actors in a use case model

Answer 7

Human i.e user
Non-human i.e. another system/time

Question 8

2 relationship types of use cases

Answer 8

1. «Include» (ALWAYS) e.g. after given bill , take payment
   - Dotted arrow with head pointing towards second piece of functionality
2. «Extend» (IF) e.g. customer order food «extend» order wine (IF the customer wants to order wine)
   - Dotted arrow with head pointing towards first piece of functionality (functionality it is dependant on)

Question 9

What can be used to support a use case diagram?

Answer 9

Use case description

Question 10

What are the main elements of a use case description?

Answer 10

Pre conditions (i.e. customer must have an account)

Step by step narrative between the system & the user

Post conditions (i.e. view what they have access to)

Should also include: Name/ID/Description/Actors/Pre-conditions/Main scenario + Alternative flows/Post-conditions

Question 11

What can a use case description be supported by?

Answer 11

A process flow diagram (rather than step by step)

Question 12

What does a use case not capture/consider?

Answer 12

Information needed / data

Question 13

Why model data?

Answer 13

To understand the meaning and the structure
Determines the data requirements of the system
It provides a common understanding of the data
It is the basis of the technical implementation
Controls redundancy and supports data integrity

Question 14

Examples of data models

Answer 14

(Entity) Relationship Diagram (ERD) & Class Diagrams

Question 15

What is a class diagram?

Answer 15

Conceptual model of the data that needs to be held

Question 16

What are the elements of a class diagram?

Answer 16

CALM

1. Classes (datagroups)
   - Things/Events/Places/People & Organisaions
2. Attributes (information to be held of the classes)
3. Logical Associations (between classes)
4. Multiplicities (How many instances one class can be associated with in another class
   - Read “Each ‘class’ is associated with #..’ of the ‘other class’”
   (5. operations)

Question 17

How should multiplicities be read?

Answer 17

At the end of the association

Question 18

What does a class model not consider?

Answer 18

Technology/Processes/Constraints (i.e time)

It is conceptual

Question 19

How is a class represented in a class model?

Answer 19

A simple rectangle with the name of the class in the top compartment

Always written as a noun phrase i.e. Customer / BankAccount (Camel case)

Question 20

What does an association represent in a class model?

Answer 20

A logical/meaningful correspondence between classes

e.g. Customer MAKES booking
Passenger TRAVELS on train

Question 21

How is an association represented in a class model?

Answer 21

A line between classes with an arrow showing how it should be read with multiplicities. It may be labelled with a meaningful description i.e. Owns vs Owned by

Question 22

How can multiplicities be documented?

Answer 22

0..2 = 0,1,2
0..* = 0 or/to many = no need to have an instance
1..* = 1 or/to many = at least one instance

Question 23

What does the CRUD Matrix help with?

Answer 23

Cross checking for consistency and completeness

Errors & Omissions

Question 24

What 2 elements are on the CRUD matrix?

Answer 24

1. Use case
2. Class

Question 25

What is prototyping and why is it useful?

Answer 25

Creating a ‘demonstration system’ to help clarify vague requirements

Question 26

Advantages of prototyping

Answer 26

Helps the user to really determine the requirements
– Especially user interface, performance, navigation paths
Validates requirements (req we’re putting forward for validation are correct/clarified)
Reduces risk of “getting it wrong”
Shows our requirements in action

Question 27

Disadvantages of prototyping

Answer 27

Can run out of control/scope creep
Can raise unrealistic expectations
Can lead user to overestimate progress
Tendency to begin designing the solution

Question 28

Types of prototypes

Answer 28

• Paper
• UI (Wireframes etc)
• Full prototype

It’s better it the prototype is not too realistic

Question 29

Examples of errors and omissions identified from CRUD

Answer 29

Use case for creating customer but nothing about deleting, is there an omission here?

A class may not have any elements of crud against use cases, is this required.?

Question 30

What do use cases do to classes within CRUD

Answer 30

Manipulate the data