Week 3

Question 1

What is the purpose of software modelling?

Answer 1

Manage complexity

Abstraction

Communication between all parties involved

Question 2

What types of software models are there? Give examples.

Answer 2

Object models - classes, objects, messages

Functional models - what it does - flow charts, state charts

Physical models

Task models - units of work, schedule, etc - e.g. Gantt chart

Question 3

What notations are there for software modelling?

Answer 3

OMT - Object modelling techniques

UML - Unified modeling language

State charts

flow diagrams

type diagrams

Question 4

What are some reasons you might use a model?

Answer 4

Quicker and easier to build than the real thing

Can be used in a simulation

Can evolve as we learn

Can choose how much detail to include

Can represent real or imaginary things

Question 5

What is the difference between diagrams and models?

Answer 5

Diagram illustrates some aspect of a system

Model provides complete view of a system at a particular stage, from a particular perspective

Model may consist of one or more diagrams

Question 6

What do different models present in UML? examples

Answer 6

Views of the system, e.g.

Use case view

Design view

Process view

Implementation view

deployment view

Question 7

With each iteration, models become more:

Answer 7

Concrete - less abstract

Formally specified

Detailed

Question 8

What is the purpose of Activity Diagrams?

Answer 8

To model a task

Describe a function of a system

Describe the logic of an operation

Question 9

How do you draw an activity diagram?

Answer 9

Identify the actions

Organise them in order

Draw arrows between them

Question 10

Activity diagrams may contain ____________ if some actions are carried out by different people

Answer 10

swimlanes

Question 11

What is the difference between static models and dynamic models/

Answer 11

Static models describe structural aspects

Dynamic models describe behavioural aspects

Question 12

Give 3 examples of static models

Answer 12

Class diagrams

Package diagrams

Type diagrams

Question 13

give 4 examples of dynamic models

Answer 13

Use case diagrams

Sequence diagrams

Collaboration diagrams

Activity diagrams

Question 14

What do use case diagrams show?

Answer 14

User view of essential system behaviour

Does NOT specify the flow of processes

Question 15

How is inheritance represented on UML class diagrams?

Answer 15

Empty triangle pointing towards the inherited class

Question 16

What does aggregation mean?

Answer 16

The class uses some other classes which have meaning on their own

Question 17

What does composition mean?

Answer 17

A class uses other classes which would have no meaning without the class using them

Question 18

What are the pros of UML?

Answer 18

De facto industry standard (or not as the case may be)

A standard of communication - commonly accepted

Question 19

What are the cons of UML?

Answer 19

Not really unified - little integration between sub notations

Not a great model - low level of abstraction

Not really a language - no well-defined semantics

Question 20

What are some of the top factors that cause projects to fail?

Answer 20

Incomplete requirements

Lack of user Involvement

Unrealistic expectations

Question 21

What are the 3 types of requirement?

Answer 21

Functional requirement - what the system does - e.g. must play music

Non-functional requirement - other requirements, e.g. must have 1MB memory

Constraints - legal, financial etc. constraints - e.g. all data must be removed after customer leaves

Question 22

What is requirements elicitation?

Answer 22

Gathering requirements from clients

Bridging the gap between non-technical people and technical people (users and software engineers)

Question 23

One of the biggest parts of building a new system to replace an old system is ______________

Answer 23

Understanding the old system and why it needs replacing

Question 24

What is the purpose of requirements languages and notations

Answer 24

To represent the requirements in an explicit, structured form

Question 25

What is the input to requirements languages and notations?

Answer 25

A report on elicited requirements

Question 26

What is the output of requirements languages and notations?

Answer 26

Formal requirement’s specifications - mathematical languages and state charts

Informal requirement specifcations - use case diagrams, class diagrams, etc.

Question 27

What should a requirements specification include?

Answer 27

Problem Definition - what is the problem

Viewpoint structure - what is the scope, who’s involved

Functional and non functional requirements

Question 28

How are <<extend>> and <<include>&gt; used on use case diagrams?</include></extend>

Answer 28

<<include>> - a task that must be done before the current task - dotted arrow drawn towards the included task</include>

<may>
</may>

Question 29

What is the purpose of a use case diagram?

Answer 29

Document the functionality of the system from users perspective

Question 30

What is the difference between requirements verification and validation?

Answer 30

Verification: compare one document to another

Validation: check requirements with customer

Question 31

What are the 5 criteria for requirements validation?

Answer 31

Correctness - requirements represent clients view

Completeness: All possible scenarious are described

Consistency - No functional or non functional requirements contradict each other

Realism - Can be implemented and delivered

Traceability - each function can be traced to a functional requirement