Week 3- Modelling

Question 1

What is a model?

Answer 1

A model a simplified representation of something. It simplifies, it allows some details to be studied and explored at the expense of other details. A MODEL IS A TOOL.

Question 2

Why are models used as a part of many design and development processes?

Answer 2

Every model is expressed in a medium that is convenient for use, and in a ‘language’ - written or visual or both - that is easy to understand.

Question 3

What is meant by the semantic aspect of a model? (Information aspect)

Answer 3

The semantic aspect communicates meaning. A model should mean something to the person or system using the model.

Question 4

What is meant by the syntactic aspect of a model? (notational aspect)

Answer 4

The semantic aspect communicates meaning. A model should mean something to the person or system using the model.

Question 5

What is meant by the concept of abstraction?

Answer 5

The level of abstraction of model is an indication of the amount of detail described by the model.
High level- low detail
Low level- lots of detail

Question 6

Why are models used as a part of many design and development processes?

Answer 6

By building models, developers learn about the system or software they are modelling, they increase their understanding. Another important benefit of having models is that they are an effective way to present information about the subject of the model – they provide a useful communication tool.

Question 7

What are the three general types or categories of modelling used with modern systems and software development?

Answer 7

Functional modelling
Structural modelling
Behavioural modelling

Question 8

When speaking about development activities what is meant by requirements?

Answer 8

To develop a complete and clear understanding of what the product – system or software - is supposed to do for its users.

Question 9

When speaking about development activities what is meant by analysis?

Answer 9

To develop a complete and clear understanding of how the product – system or software – can be constructed.

Question 10

When speaking about development activities what is meant by design?

Answer 10

To develop a complete and clear design for the final product.

Question 11

When speaking about development activities what is meant by implementation?

Answer 11

To build an example of the system or software that meets the original requirements.

Question 12

What do all development activities have in common?

Answer 12

They all produce a product.

Question 13

What is the purpose of functional modelling?

Answer 13

To explore, understand and document the EXTERNAL behaviour of the system or software. It is about the system and how it interacts with the system users.

Question 14

What is the purpose of structural modelling?

Answer 14

The internal aspects of a system or software that are unchanged while it is used.

Question 15

What is the purpose of behavioural modelling?

Answer 15

They describe the internal logic of activities and processes without specifying how the processes are to be implemented.

Question 16

What are four UML modelling tools used commonly for dynamic modelling?

Answer 16

Activity diagrams
Sequence diagrams,
Collaboration diagrams
Statechart diagrams

Question 17

What are the nine types of modelling diagrams used by UML?

Answer 17

* Use case diagrams
• Class diagrams
• Object diagrams
• Sequence diagrams
• Collaboration diagrams
• Statechart diagrams
• Activity diagrams
• Component diagrams, and
• Deployment diagrams

Question 18

What is a use-case?

Answer 18

A use-case is a sequence of actions that the system will perform to achieve an outcome for the user.

Question 19

What are the common symbols used in a use-case diagram?

Answer 19

Actor- Stick person
Use-case- oval
Relationship- straight line

Question 20

What is a ‘use-case behaviour description’?

Answer 20

The purpose of each use-case description is to describe the sequence of actions that will take place between the actor and the system in order to perform and complete the use-case. Note that a use-case description does not attempt to describe any of the detailed activities that must take place inside the system (or inside the actor).

Question 21

What are the two common methods for writing a ‘use-case behaviour description’?

Answer 21

Narrative and column description

Question 22

What is another name used for structural modelling?

Answer 22

Static or conceptual

Question 23

What is a class diagram?

Answer 23

Class diagrams are visual ways to document the definition of a class by describing its name, its property members and its method members.

Question 24

How are classes and objects related to each other?

Answer 24

An object is a specific instance of a class. A class defines what properties will be used to describe every object based on this class. Two objects of the same class will have the same collection of properties, but they will have at least one property that has a different value in each of the objects – if all the properties have the same values in both of the two objects then they are the same object.

Question 25

What is meant by a relationship between classes?

Answer 25

Object-orientation recognises that different objects of different classes work together to create the structure and functionality of larger systems. This means that in any particular system, classes have relationships with each other.

Question 26

What are the common types of relationships between classes?

Answer 26

An association relationship takes place when one object uses or collaborates with another independent object.
An aggregation occurs if one class is a
member of another class and where the ‘inside’ class is one that can also exist as a separate entity
A composition occurs if one class is a member of
another class and where the ‘inside’ class is one that cannot exist as a separate entity.
Generalisation or inheritance.

Question 27

What is the multiplicity of a class relationship?

Answer 27

The multiplicity of an association is a deeper concept. It is needed because in many systems, an association between two classes, like students and dogs, can involve multiple instances of each class.

Question 28

What is the naming convention for objects?

Answer 28

ObjectName:ClassName.
Eg lost:cat
best:student

Question 29

What are the four basic multiplicities?

Answer 29

one to one
one to many
many to one
many to many

Question 30

What is another name used for behavioural modelling?

Answer 30

Dynamic modelling

Question 31

What are some common behavioural modelling tools?

Answer 31

Activity modelling (work flow)

Question 32

What is an activity diagram?

Answer 32

An activity diagram considers that almost any workflow is made up of combinations of activities, states and transitions. An activity is an identifiable unit of work that must be carried out – it is a step, task or process, it does something.

Question 33

What is pseudo-code?

Answer 33

Pseudo-code is a traditional way of describing a process that uses a mixture of English text and programming-like statements.

Question 34

What are the main symbols in an activity diagrams?

Answer 34

Activity- Rectangle with rounded ends
State- Rectangle with rounded corners
Transition- A line with an arrow on it
Start state- solid circle
End state- solid circle in another circle
Decision Point- a diamond
Forks and Joins
Swim lanes