1. Systems Analysis and Design I
Revision Class
May 20th 2019

2. Contents Level 4, 15 credits Module code: COIY016H4
Lecture
Date
Lab
Remark W1
Introduction, IS development
Object-orientation fundamentals
Jan 14
None W2
Jan 21 W3
Modelling concepts, activity diagram
Jan 28 W4
Requirements, use cases
Feb 4 W5
Class diagrams+Project Tutorial
Feb 11
Test 1 W6
Sequence diagrams
Feb 18
Group Project 1 W7
State diagrams 1+Project Tutorial
Feb 25
Group Project 2 W8
State diagrams 2+Project Tutorial
Mar 4
Group Project 3 W9
Mar 11
Group Project 4
Test 2
W10
System design+Project Tutorial
Mar 18
Group Project 5
Make-up Test 1
W11
Version control+Project Tutorial
Mar 25
Group Project 6
Make-up Test 2
Level 4, 15 credits
Module code: COIY016H4
All material is available:

3. Assessment Coursework (20%) Examination (80%)
2 In-Class Tests (5% each)
25 Multiple-Choice Questions (in 25 mins)
Test 1 (on Week 5, Feb 11)
Test 2 (on Week 9, Mar 11)
Both questions and answers have been uploaded to Moodle
1 Group Project (10%)
50 Marks
Evaluation
Quality of your report: 25 marks.
Feedback from your peers: 25 marks.
Examination (80%) 3

4. Examination 2-hour exam, FOUR questions, 100 marks
Past papers is available
[under “information systems concepts”]
Two different types of questions:
Short-answer questions
(Small) case studies with UML modelling

5. Examples
What are the advantages of the traditional waterfall lifecycle (TLC)? (5 marks)
Answer:
Tasks in phases may be assigned to specialised teams. (1 mark)
Project progress is evaluated at the end of each phase. (2 marks)
TCL can be used to manage projects with high levels of risks. (2 marks)
You will see FIVE short-answer questions in the exam, each of them is worth 5 marks
Suggestion: look at the past papers, go through all of those questions and try to answer them
Read the slides and textbook please!

6. UML Modelling UML2 defines 14 types of diagrams Structure Behaviour
Class Diagram, Object Diagram
Component Diagram, Package Diagram, Profile Diagram
Composite Structure Diagram, Deployment Diagram
Behaviour
Use Case Diagram
Activity Diagram, State Machine Diagram
Interaction
Sequence Diagram, Communication Diagram
Timing Diagram, Interaction Overview Diagram 6 6

7. Activity diagrams
Used to model high-level business tasks and system functions
action node
rectangle with rounded corners and a meaningful name
action edge (control flow)
open arrow
Add a New Client
Action exists to carry out some task.
Action exists to carry out some task.
The flow implies that as soon as the first action is complete, the next action is started.
Assign Staff Contact
The flow implies that as soon as the first action is complete, the next action is started. 7 7

8. Notation of Activity Diagrams
initial node
black circle
decision node merge node
diamond
guard condition
in square brackets
final node
black circle in white circle
[campaign to add]
[no campaign to add]
Add a New Client
Assign Staff Contact
Add New
Campaign
The flow of control will follow along the first control flow with a guard condition that evaluates to true. 8 8

9. Tips on Activity Diagrams
[no staff to assign]
Add a New Client
Assign Staff Contact
Add New
Campaign
[campaign to add]
[no campaign to add]
Assign Staff
to Campaign
[staff to assign]
Iteration or loop can be represented
Multiple flows from an action are implicitly AND-ed
Guard conditions do not have to be mutually exclusive, but it is advisable that they should be
If they are not, you need to specify the order of evaluation (otherwise the results will be unpredictable)
Decisions should be strictly nested, but a merge point can be combined with the following decision point 9 9

10. Notation of Activity Diagrams
fork node join node
thick bar
actions carried out in parallel
Add a New Client
Assign Staff Contact
Add New
Campaign 10 10

11. Self-Check of activity diagrams
Action
Nodes
action node, decision node, initial node, final node, merge node, fork node, join node
Edges: action edge, guard conditions
OO related: class name, operation name, object flow, activity partition
Interrupting edge is activity edge expressing interruption for regions having interruptions. It is rendered as a lightning-bolt 11 11

12. Use case diagram
Use Cases – descriptions of the functionality of the system from the users’ perspective.
Use Case diagrams
show which users will communicate with the system
define the scope of the system
Use Case descriptions
specify the interaction between the users (actors) and the system for each use case as the users see it
could be further elaborated by communication/sequence diagrams.

13. System or subsystem boundary
Use Case Diagram
Four aspects:
actors
use cases
Communication association
system/subsystem boundary
System or subsystem boundary
Actor
Use case
Communication
association
Staff Contact
Change
a client contact 13 13

14. Extend and Include relationships
Use Case Diagrams:
Extend and Include relationships
The extend and include relationships between Use Cases
shown as stereotyped dependencies
[a stereotype is a special use of a model element that is
constrained to behave in a particular way]
Stereotype are shown by using a keywork in match guillemets
«extend» and «include» (text strings in guillemets)
Warning: easy to confuse extend and include!
Dependencies
Extend and Include relationships between use cases
shown as stereotyped dependencies
stereotypes are written as text strings in guillemets: «extend» and «include» 14 14

15. Use Case Diagrams: «extend»
Extend means: One use case provides additional functionality that may be required in another use case
“does something over and above what is done”
There may be multiple ways of extending a use case
represent variations in the way that actors interact with the use case
Rather than capturing all variations in one use case, document the core functionality in one and then extend it with other
The extension points show when the extension occurs
A condition can be placed in a note joined to the dependency arrow 15 15

16. Use Case Diagrams: «extend»
Campaign Manager
Check campaign
budget
summary
«extend»
Print campaign
Summary print
extension points
Condition {print option selected}
extension point: Summary print
Note: is not put in square brackets, unlike conditions in other diagrams.)
Fig. 6.7 16 16

17. Use Case Diagrams: «include»
When there is a sequence of behaviour that is used frequently in a number of use cases
Want to avoid copying the same description everywhere
separate out the sequence of behaviour that is used in many use cases
One use case includes the functionality of another use case
A use case may include more than one other
Do not overuse: Should not be used to create a hierarchical functional decomposition of the system 17 17

18. Assign staff to work on a campaign
Use Case Diagrams: «include»
Campaign Manager
«include»
Find campaign
Assign staff to work on a campaign
Fig 6.8 18 18

19. Note: you do NOT need to show all the details of the extension points

20. Use Case Diagrams: Generalisation
Between use cases:
there may be similar use cases with common functionality
best represented by generalising out that functionality in to a “super-use-case”
shows that one use case provides
all the functionality of the more generalised use case and
some additional functionality
Between actors:
shows that one actor can participate in all the associations with use cases
the more specific actor can plus some additional use cases 20 20

21. Use Case Diagrams: Generalisation
Record completion
of an advert
Staff Contact
Change
a client contact
Fig. 6.10
Super use case
Assign individual staff to work on a campaign
Assign staff to work on a campaign
Assign team of staff to work on a campaign
Campaign
Manager 21 21

22. Use Case Descriptions
Using a step-by-step breakdown of interaction between actor and system
Assign staff to work on a campaign
Actor Action System Response
1. The actor enters the client name. 2. Lists all campaigns for that client.
3. Selects the relevant campaign Displays a list of all staff members not already allocated to this campaign.
5. Highlights the staff members 6.Presents a message confirming
to be assigned to this campaign. that staff have been allocated.
Alternative Courses
Steps 1–3. The actor knows the campaign name and enters it directly.
scenario
Referred to
as scenario 22 22

23. Class diagrams class name compartment attributes compartment
Class (and Object/Instance)
Stereotypes
Attributes (and State)
Associations (and Links)
Multiplicity
Operations
Client
companyAddress
company
companyFax
companyName
companyTelephone
class name compartment
attributes compartment
Only staff members in the role of staff contact can participate in this association
operations compartment 23

24. direction in which name should be read (optional)
association
association role
Client
StaffMember
companyAddress
staffContact
staffName
company
staffNo
liaises with
companyFax
staffStartDate
companyName
Only staff members in the role of staff contact can participate in this association
companyTelephone
association name
direction in which name should be read (optional)
Only staff members in the role of staffContact can participate in this association 24 24

25. Association End association role
Professor "playing the role" of author is associated with textbook end typed as Book.
The idea of the role is that the same class can play the same or different roles in other associations. For example, Professor could be an author of some Books or an editor.

26. Multiplicity
The multiplicity of an association is the range of permitted cardinalities of its participating objects (i.e., #objects that can participate in the association)
Decided by business rules.
for example:
any bank customer may have one or more accounts
every individual account is for one, and only one, customer
n: exactly n
*: any number
m..n: any number in the range m to n (inclusive)
0..1: optional (i.e., either none or 1)
1..*: at least one 26 26

27. Aggregation and Composition
Two special types of association
Aggregation represents a whole-part relationship between classes
Composition (or Composition aggregation) is based on the concept of aggregation
Composition expresses a similar relationship but differs in showing a stronger form of ownership by the whole
Each part may belong to only one whole at a time.
When the whole is destroyed, so are all its parts. 27 27

28. Composition vs aggregation
In both aggregation and composition object of one class "owns" object of another class.
But there is a subtle difference.
In Composition the object of class that is owned by the object of it's owning class cannot live on it's own
Also called "death relationship".
It will always live as a part of it's owning object
In Aggregation the dependent object is standalone and can exist even if the object of the owning class is dead.
So in composition if owning object is garbage collected the owned object will also be which is not the case in aggregation.
Confused?
Composition Example : Consider example of a Car and an engine that is very specific to that car (meaning it cannot be used in any other car). This type of relation ship between Car and SpecificEngine class is called Composition. Object of Car class cannot exist without object of SpecificEngine class and object of SpecificEngine has no significance without Car class. To put in simple words Car class solely "owns" the SpecificEngine class.
Aggregation Example : Now consider class Car and class Wheel. Car needs a Wheel object to function. Meaning Car object own Wheel object but we cannot say Wheel object has no significance without Car Object. It can very well be used in a Bike, Truck or different Cars Object.
Aggregation and Composition are subsets of association meaning they are specific cases of association.

29. unfilled diamond denotes aggregation
Notation: Aggregation
A student could be in a number of modules
If a module is cancelled, students are not destroyed
Module
Student
0..*
1..*
unfilled diamond denotes aggregation
“Owing” class 29 29

30. filled diamond denotes composition
Notation: Composition
An ingredient is in only one meal at a time
If you drop your meal on the floor, you probably lose the ingredients too
Meal
Ingredient
1..* 1
filled diamond denotes composition
“Owing” class 30 30

31. Small trick Trick to remember the difference : has A -- Aggregation
Own -- cOmposition
So in composition if owning object is garbage collected the owned object will also be which is not the case in aggregation.
Confused?
Composition Example : Consider example of a Car and an engine that is very specific to that car (meaning it cannot be used in any other car). This type of relation ship between Car and SpecificEngine class is called Composition. Object of Car class cannot exist without object of SpecificEngine class and object of SpecificEngine has no significance without Car class. To put in simple words Car class solely "owns" the SpecificEngine class.
Aggregation Example : Now consider class Car and class Wheel. Car needs a Wheel object to function. Meaning Car object own Wheel object but we cannot say Wheel object has no significance without Car Object. It can very well be used in a Bike, Truck or different Cars Object.

32. Adding Generalization Structure
Figure 8.2 32 32

33. Class Diagrams Checklist
Requirements Model
→ Analysis Model
→ Design Model
To Draw a class diagram
Identify Classes
Determine Stereotypes
Find and Locate Attributes
Add Associations
Determine Multiplicity
Find and Locate Operations
Class (and Object/Instance)
Stereotypes
Attributes (and State)
Associations (and Links)
Multiplicity
Operations 33 33

34. Sequence diagram Frame label Sequence diagram is enclosed in a frame
:Client
:Campaign
:Advert
getName
listCampaigns
listAdverts
Advert
newAd:Advert
addNewAdvert
Lifeline
Activation or Execution
Object creation
:CampaignManager
sd Add a new advert to a campaign
loop
Interaction Operator
Interaction Constraint
Combined Fragment
(loop)
[For all client’s campaigns]
getCampaignDetails
[For all campaign’s adverts]
getAdvertDetails
Frame label
Sequence diagram
is enclosed in a
frame
“sd” is used to determine the interaction diagram; interaction

35. Sequence Diagrams: Example
Figure 9.4 on p. 265
:LifelineA
:LifelineB
Synchronous (blocking) message
sd Interaction Name
msg a
Send message
Event Occurrence
(msg.sendEvent)
Receive messaged Event Occurrence
(msg.recieveEvent)
start of
Execution Occurrence
end of
Active
State on lifeline showing pre-condition
Message reply showing return of control 36 36

36. Figure 9.16 on p. 275 alt interaction operator shows branching
:Client
:Campaign
:Advert
getName
listCampaigns
ref
:CampaignManager
Advert
addCostedAdvert
newAd:Advert
newRequest:Request
alt
[else]
sd Add a new advert to a campaign if within budget
List client campaigns
[totalCost <= budget]
Request
Get campaign budget
alt interaction operator
shows branching
Two interaction operands,
one for each alternative
Figure on p. 275 38 38

37. Example
Suppose you are developing an online university enrollment system. Create a use case diagram for the following requirements.
(a) The system should enable the academic staff to examine the modules offered by their department, add and remove modules, and change the information about them (e.g., the maximum number of students permitted). (6 marks)
(b) It should permit students to examine currently available modules, add and drop modules from their schedules and examine the modules for which they are enrolled. (6 marks)
(c) Department staff (i.e., academic and administrative staff) should be able to print a variety of reports about the modules and the students enrolled in them. (7 marks)
(d) The system should ensure that no student takes too many modules and that students who have any unpaid fees are not permitted to register. (6 marks)

38. Answer
(a) The system should enable the academic staff to examine the modules offered by their department, add and remove modules, and change the information about them (e.g., the maximum number of students permitted).
(b) It should permit students to examine currently available modules, add and drop modules from their schedules and examine the modules for which they are enrolled.
(c) Department staff (i.e., academic and administrative staff) should be able to print a variety of reports about the modules and the students enrolled in them.
(d) The system should ensure that no student takes too many modules and that students who have any unpaid fees are not permitted to register.

39. Example
Suppose you are developing a point-of-sale system that manages the checkout process in a supermarket. Create a class diagram for the following requirements. (a) Each transaction includes at least one item. Date and time of each transaction must be recorded. (4 marks) (b) Items can be coded or weighted. Coded items have code. Weighted items have price per kg and weight. All items have a method of calculating their price. (6 marks) (c) Some customers have loyalty cards. Only one loyalty card may be used in a transaction.(4 marks) (d) No transaction can be completed without a payment and each payment is made for a single transaction. (5 marks) (e) A payment can be made in cash or by debit/credit card. Cash payments record the amount given and change. Card payments record card number and bank authorization code.(6 marks)

40. Answer

41. In the exam You will encounter THREE such questions in the exam
Each one asks you to develop one UML diagram which might be
Activity diagram, class diagram, sequence diagram, use case diagram
Each question is worth 25 marks.
Suggestion: look at the past papers, go through all of those questions and try to come up with UML diagram by yourself

42. Good luck!