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SAD2 - UMLSAD2 - UML44thth Lecture Lecture

Class Diagram in Construction PhaseClass Diagram in Construction Phase

PatternsPatterns

Case StudyCase Study

Lecturer: Dr Dimitrios MakrisLecturer: Dr Dimitrios Makris((d.makris@kingston.ac.uk))

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Last week

Class Diagram Basic Notation Review Some Advanced Notation

Other Static Views Package Diagram

Workshop: Class Diagram (Conceptual Modelling)

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Summary of this session Class Diagram in Construction

Phase Patterns Case Study

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Class Diagrams in Construction phase (Design)

Add implementation details Classes, operations, attributes,

multiplicity, navigability, visibility, etc. How?

Exploit interaction diagrams Use patterns (“GRASP”, “Gang of

Fours’s”)

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Exploit Interaction Diagram

Collaboration diagram or Sequence diagram?

Work in parallel on both Interaction & Class diagrams

Identify new classes Add operations Add multiplicity and navigability Enhance attributes Determine visibility

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Patterns Patterns are general solutions to common problems Part of software development method, not part of

UML GRASP (General Responsibility Assignment Software

Patterns) by Graig Larman Expert, Creator, Controller, Low Coupling, High Cohesion,

Polymorphism, Pure Fabrication, Indirection, “Don’t Talk to Stangers”.

Gang of Four’s Patterns by E. Gamma, R. Helm, R. Johnson & J. Vlissides 25 patterns divided in 3 categories according to their

purpose (creational, structural, behavioural)

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Some GRASP Patterns Expert Creator High Cohesion Low Coupling

Law of Demeter Controller Façade Class

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GRASP: Expert Problem: “Who, in the

general case is responsible?”

Solution: Assign a responsibility to the information expert -- the class that has the information necessary to fulfill the responsibility.

e.g: Assign calculate_total() behaviour

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GRASP: Creator Problem: Who creates? Solution: Assign class B the

responsibility to create an instance of class A if one of the following is true: B contains A B aggregates A B has the initializing data for

A B records A B closely uses A

e.g: New PurchaseOrder has been created. Which class is responsible for creating its order lines?

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GRASP: High Cohesion Problem: How to

keep complexity manageable?

Solution: Assign responsibilities so that cohesion remains high.

e.g: Consider the LiftController class. Is it cohesive?

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GRASP: Low Coupling Problem: How to

support low dependency and increased reuse?

Solution: Assign responsibilities so that coupling remains low.

e.g: What are the disadvantages of this class diagram? How can they be solved?

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Law of Demeter:Don’t Talk to Strangers

Use the “Law of Demeter” to reduce coupling. Within a method, messages can only be sent

to the following objects: The this object (or self). A parameter of the method An attribute of self. An element of a collection which is an attribute of

self. An object created within a method

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GRASP: Controller Problem: Who

handles a system event?

Solution: Introduce a controller class which will be between the actor and the other classes.

E.g: Should “Race” be responsible for displaying its details?

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Façade Pattern

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Case study

Let say that we want to develop a email-client program!

How will we use the UML diagrams through an iterative-incremental development process?

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Recall the Unified Process Stages Inception Phase Elaboration Phase

Capture Requirements Model Domain Design Architecture

Construction Phase Analysis Design Coding Testing

Transition Phase

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Inception Phase Inception Phase Elaboration Phase

Capture Requirements Model Domain Design Architecture

Construction Phase Analysis Design Coding Testing

Transition Phase

We have already done that by deciding that we will develop an email client application

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Use Case Diagram Inception Phase

Elaboration Phase Capture Requirements Model Domain Design Architecture

Construction Phase Analysis Design Coding Testing

Transition Phase

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Conceptual Model (Class Diagram)

Inception Phase

Elaboration Phase Capture Requirements

Model Domain Design Architecture

Construction Phase Analysis Design Coding Testing

Transition Phase

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Package Diagram If the scope of the

project is large, then we can split it into smaller manageable pieces, using the package diagram

Inception Phase

Elaboration Phase Capture Requirements Model Domain

Design Architecture Construction Phase

Analysis Design Coding Testing

Transition Phase

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Use Case Full Text Inception Phase Elaboration Phase

Capture Requirements Model Domain Design Architecture

Construction Phase Analysis Design Coding Testing

Transition Phase

Pre-requirements: An Account exists and is selected

Post-requirements: Email sent to the SMTP Server, Message copied to the Outbox Folder

Main Success Scenario: The User selects “Compose Message”. The user edit the fields “To:”, “Cc:”, “Subject”, “Message”. Then, the user selects “Send Message”.

Exceptions: SMTP Server undefined or cannot connect, “To:” undefined

Alternative Scenario: The user selects “Send Message Later”, instead of “Send Message”.

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Activity Diagram Inception Phase Elaboration Phase

Capture Requirements Model Domain Design Architecture

Construction Phase Analysis Design Coding Testing

Transition Phase

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Sequence Diagram

Inception Phase Elaboration Phase

Capture Requirements Model Domain Design Architecture

Construction Phase Analysis

Design Coding Testing

Transition Phase

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Dynamic viewsin Construction Phase

Other Dynamic Views can be used for the Analysis and the Design Step, e.g: Collaboration Diagram

(Communication in UML2.0) State Diagram Interaction Overview

Diagram

Inception Phase Elaboration Phase

Capture Requirements Model Domain Design Architecture

Construction Phase Analysis Design Coding Testing

Transition Phase

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Implementation Model (Class Diagram)

Inception Phase Elaboration Phase

Capture Requirements Model Domain Design Architecture

Construction Phase

Analysis

Design Coding Testing

Transition Phase

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Coding Inception Phase Elaboration Phase

Capture Requirements Model Domain Design Architecture

Construction Phase

Analysis Design

Coding Testing

Transition Phase

From Class Diagrams to Class Definitions

From Dynamic Views to Method Definitions

Packages in Java, C++ and C#

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From Class Diagram to Class Definitions

public class OrderLine{

private int Quantity;private SKU SKUOrdered;

public OrderLine(int qty, SKU product);public int GetQuantity();public int SetQuantity(int qty);public float Subtotal();

}

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From Interactive Diagrams to Method Definitions

..public double GetTotal(){

double total=0;OrderLine line;for (int i=0; i<OrderLineList.size(); i++){

line = (OrderLine) OrderLineList.get(i);

total+= line.GetSubtotal();}return total;

}

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Test & Party! Inception Phase Elaboration Phase

Capture Requirements Model Domain Design Architecture

Construction Phase

Analysis Design Coding

Testing Transition Phase

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Construction Phase iterations

Do the same for each Use Case

Inception Phase Elaboration Phase

Capture Requirements Model Domain Design Architecture

Construction Phase Analysis Design Coding Testing

Transition Phase

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Promote and Sell the System!

Inception Phase Elaboration Phase

Capture Requirements Model Domain

Construction Phase Analysis Design Coding Testing

Transition Phase

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Summary The implementation model is easily

derived from the conceptual model and the sequence/collaboration diagrams.

Patterns are standardised solutions to common problems

A case study illustrated the usage of UML in different steps of the Unified Process.

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What is next? This week

Workshop on Class Diagram (Implementation Model)

Next week Feedback on workshop exercises Discuss the assignment