Transcript SAD2-UML_Lecture_4[1..
SAD2 - UML
4 th Lecture Class Diagram in Construction Phase Patterns Case Study Lecturer: Dr Dimitrios Makris ( [email protected]
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Last week
Class Diagram Basic Notation Review Some Advanced Notation Other Static Views Package Diagram Workshop: Class Diagram (Conceptual Modelling) 2
Summary of this session
Class Diagram in Construction Phase Patterns Case Study 3
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”) 4
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 5
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) 6
Some GRASP Patterns
Expert Creator High Cohesion Low Coupling Law of Demeter Controller Façade Class 7
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 8
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 12
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 16
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 17
Use Case Diagram
Inception Phase Elaboration Phase Capture Requirements Model Domain Design Architecture Construction Phase Analysis Design Coding Testing Transition Phase 18
Conceptual Model (Class Diagram)
Inception Phase Elaboration Phase Capture Requirements Model Domain Design Architecture Construction Phase Analysis Design Coding Testing Transition Phase 19
Package Diagram
Inception Phase Elaboration Phase Capture Requirements Model Domain Design Architecture Construction Phase Analysis Design Coding Testing Transition Phase If the scope of the project is large, then we can split it into smaller manageable pieces, using the package diagram 20
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 22
Sequence Diagram
Inception Phase Elaboration Phase Capture Requirements Model Domain Design Architecture Construction Phase Analysis Design Coding Testing Transition Phase 23
Dynamic views in Construction Phase
Inception Phase Elaboration Phase Capture Requirements Model Domain Design Architecture Construction Phase Analysis Design Coding Testing Transition 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 24
Implementation Model (Class Diagram)
Inception Phase Elaboration Phase Capture Requirements Model Domain Design Architecture Construction Phase Analysis Design Coding Testing Transition Phase 25
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# 26
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(); 27
From Interactive Diagrams to Method Definitions
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public double GetTotal() { double total=0; OrderLine line; for (int i=0; i Inception Phase Elaboration Phase Capture Requirements Model Domain Design Architecture Construction Phase Analysis Design Coding Testing Transition Phase 29 Inception Phase Elaboration Phase Capture Requirements Do the same for each Use Case Model Domain Design Architecture Construction Phase Analysis Design Coding Testing Transition Phase 30 Inception Phase Elaboration Phase Capture Requirements Model Domain Construction Phase Analysis Design Coding Testing Transition Phase 31 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. 32 This week Workshop on Class Diagram (Implementation Model) Next week Feedback on workshop exercises Discuss the assignment 33Test & Party!
Construction Phase iterations
Promote and Sell the System!
Summary
What is next?