A Student Guide to ObjectOrientated Development
Chapter 9 Design
1
Design

Analysis describes WHAT a system must
do
 Design describes HOW to do it

Analysis decisions are implementationindependent
 Design decisions are implementationdependent
2
Design
Design activities:
overall system design
 detailed design

3
Overall system design
designing the overall architecture of
the system
 selecting a strategy for coping with
persistent data
 designing a user interface
 choosing software and hardware
platforms
 producing a test plan

4
Design - overall
Product of overall design activities





layered diagram of the system
architecture
a set of component and deployment
diagrams
a database definition
a test plan
screen and report layouts
5
Design - detailed
Product of detailed design activities
 a set of detailed class diagrams
 supporting documentation such as
data dictionary and operation
specifications
 a set of detailed interaction diagrams
6
Architecture
Architecture describes the software
and hardware components of the
system
7
Architecture -software
logical software components :
classes, packages, subsystems
Modelled with class diagrams etc.
 physical software components :
executable files, class libraries and
databases
Modelled with component diagrams

8
Architecture - hardware
Hardware architecture :
 the computers, peripherals and
networks on which the system will
run
 hardware architecture is modelled
using deployment diagrams.
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Packages and dependencies

A package is a UML mechanism for
grouping modelling elements

Does not represent anything in the
system, but is used to group modelling
elements that do

Can be used to group use cases, classes,
collaborations, sub-systems etc
10
We can also use packages to nest models
Hire Bike
Level 1 Package
diagram of subsystems
Manage
Data
Bike
Customer
Level 2 class
diagram for
Manage Data
sub-system
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Dependencies
A dependency exists between
packages if a change in one can affect
the other.
 If a change in package A can affect
package B, then package B depends on
package A.

12
Dependencies
Dependency
Package A
Package B
13
Dependencies

A dependency exists between two
classes if they have a client-server
relationship
14
Layered architecture

In a layered architecture, packages are
arranged into layers so that each layer
only uses the services of the layer
below it.
Layer 6
Layer 5
Layer 4
Layer 3
Layer 2
Layer 1
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Layered architecture
the presentation layer near the top
 data storage layer towards the
bottom
 application layers in the middle

16
Layered architecture
User Interface
Application
Logic
Application
Database
Presentation layer
Application logic layer
Application layer
Storage layer
17
Implementation diagrams
 Component
diagram - models
physical software components
 Deployment diagram - models
hardware components
18
Component diagram
Maintenance.java
Hiring.java
Database
19
Deployment diagram
Database
Server
Database
Shop PC
Maintenance.java
Reception PC
Hiring.java
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User interface
Should be consistent:
 screen layouts should follow the
same general pattern
 similar tasks should be performed in
similar ways
 messages from the system to the
user should always be in the same
format.
·
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User interface

User tasks that are boring and prone to error
should be minimized
 system should provide shortcuts for experienced
users
 data should be entered by selecting from a menu
rather than typing
 screens should be free of clutter, containing all
the relevant information and no more. An
overcrowded screen is tiring to look at and
irritating to work with.
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User interface - example
23
Dealing with persistent data
Object-oriented and relational databases
• A database stores, organizes and maintains data to support
the operations of an organization
•An object-oriented database provides the facilities of a
traditional database, and supports the complex data structures
of object-oriented systems
•However, for an information system, such as Wheels, a
developer would be much more likely to choose a relational
database.
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Dealing with persistent data
Object-oriented and relational databases
• Relational databases are established, proved
efficient for the sort of data found in information
systems like Wheels
• Object-oriented databases relatively recent
• Business organizations have invested money in
relational database systems - reluctant to throw it
away in order to change to an object-oriented
database
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Dealing with persistent data
Linking an object-oriented program to a relational database
• For an O-O program to access a relational database we need
code to establish a connection
• JDBC (Java Database Connectivity) - interface that interacts
with both the code and the database
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Implementing a class diagram in a relational
database
Basic rule - one class maps to one table
Bike
bike#
available
type
size
make
model
dailyHireRate
deposit
Bike class
Primary key
Bike table
Bike
No.
Available Type
Size
Make
Model
249
250
251
252
253
On hire
Available
On hire
On hire
Available
woman's
man's
woman's
man's
child's
Scott
Raleigh
Scott
Dawes
Raleigh
Atlantic Trail
Pioneer
Atlantic Trail
Galaxy
Chopper
mountain
tourer
mountain
tourer
mountain
Daily
Hire
Rate
£8.00
£9.00
£8.00
£8.00
£5.00
Deposit
£50.00
£60.00
£50.00
£50.00
£25.00
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Implementing a one to many association in a relational
database: First method
Customer
custID
name
address
tel
CustID
1
2
3
4
5
Payment
date
1..* totalAmountPaid
totalDepositPaid
totalDepositReturned
1
Name
Sykes
Perle
Hargreaves
James
Robins
FirstName
Jim
Lee
Les
Sheena
Charlie
Payment No. Date
401
402
403
404
405
CustID
1
2
2
3
11
19/03/04
19/03/04
19/03/04
20/03/04
20/03/04
Street
2 High Road
14 Duke Street
11 Forest Road
4 Duke Street
11 Juniper Road
Town
Greenwood
Greenwood
Prestwich
Albans
Greenwood
Greenwood
PhoneNo
01395 211056
01395 237851
01462 501339
01395 237663
0 1395 267843
Total amount
paid
Total deposit
paid
Total deposit
returned
£56.00
£20.00
£145.00
£186.00
£44.00
£50.00
£25.00
£80.00
£100.00
£40.00
£50.00
£25.00
£80.00
£84.00
£40.00
Payment No.
409
513
405
404
501
One to many association
Customer table
Payment table
Customer-Payment table
28
Implementing a one to many association in a relational
database: Second method
Customer
custID
name
address
tel
Payment
date
1..* totalAmountPaid
totalDepositPaid
totalDepositReturned
1
One to many association
Customer
CustID
1
2
3
4
5
Name
Sykes
Perle
Hargreaves
James
Robins
Street
2 High Road
14 Duke Street
11 Forest Road
4 Duke Street
11 Juniper Road
Town
Greenwood
Greenwood
Prestwich
Albans
Greenwood
Greenwood
PhoneNo
01395 211056
01395 237851
01462 501339
01395 237663
0 1395 267843
Customer table
foreign key
Payment
Payment No. CustID
411
412
413
414
415
FirstName
Jim
Lee
Les
Sheena
Charlie
17
20
6
3
17
Date
Total amount
paid
Total deposit
paid
Total deposit
returned
19/03/04
19/03/04
19/03/04
20/03/04
21/03/04
£56.00
£20.00
£145.00
£186.00
£44.00
£50.00
£25.00
£80.00
£100.00
£40.00
£50.00
£25.00
£80.00
£84.00
£40.00
Payment table
with foreign key
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Implementing a inheritance in a relational database
Bike
Inheritance relationship
bike#
available
type
size
make
model
dailyHireRate
deposit
SpecialistBike
epoch
insurance
normal bikes
Bike
No.
249
Available
Type
Size
Make
Model
On hire
mountain
woman's
Scott
250
251
Available
On hire
tourer
mountain
man's
woman's
Raleigh
Scott
252
253
254
On hire
Available
Available
tourer
mountain
tandem
man's
child's
man's
Dawes
Raleigh
Sunbeam
Atlantic
Trail
Pioneer
Atlantic
Trail
Galaxy
Chopper
Voyager
Epoch
1930s
Insurance
£15.00
Daily Hire
Rate
£8.00
Deposit
£9.00
£8.00
£60.00
£50.00
£8.00
£5.00
£20.00
£50.00
£25.00
£100.00
£50.00
specialist bike
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