week08. review schedule weeks 8-14 this week o review last class o introduce class diagrams o...

Engineering Quality Software

Week08

Agenda Review Schedule Weeks 8-14 This week

o Review last classo Introduce Class Diagramso ICE-03

SheridanSYST30009 - Engineering Quality

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Class Diagrams- Objectives

Identify and analyze the objects and object-classes needed in a system

Learn how to identify and represent relationships between object classes.

Learn how to identify and create super/subclass relationships

Learn how to create a Unified Modeling Language (UML) class diagram using System Architect


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Events and Use Cases

Use case o Activity the system carries outo Entry point into the modeling process

Event decomposition: help identify use cases Elementary business processes (EBPs)

o Basic unit of analysiso Initiated by event occurring at specific time and

placeo Discrete system response that adds business

value


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Event Decomposition

Event decomposition o Develops use cases based on system response to events o Focus on business processes and business requirements

Result of the decomposition:o List of use cases triggered by business events o Use cases at the right level of analysis


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Problem Domain Classes

Problem domaino Set of work-related “things” in system

component • Things have data representation within system

o Examples: products, orders, invoices, customers

OO approach to things in problem domaino Objects that interact in the system

Identify and understand things in problem domaino Key initial steps in defining requirements


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Types of Things Things can be identified with methodology

Separate the tangible from the intangible

Include information from all types of users

Ask important questions about nature of event o “What actions upon things should be acknowledged

and recorded by the system?”


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Procedure for Developing an Initial List of Things

List nouns users mention when discussing system

Event table as source of potential things

o Use cases, external agents, triggers, response

Select nouns with questions concerning relevance

o Further research may be needed


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Pharmacy System as Illustration

Next Step…Associations among Things

Analyst document entity associations ( relationships)o Example: “Is placed by” and “works in”

Associations apply in two directionso Customer places an order o An order is placed by a customer

Multiplicity: the number of associations o One to one or one to many

The associations between types of thingso Unary (recursive), binary, n-ary


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Associations Naturally Occur between Things


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Multiplicity of Relationships

Attributes of Things

Specific details of things are called attributes

Analyst should identify attributes of things

Identifier (key): attribute uniquely identifying thing

o Examples: Social Security number, vehicle ID number, or product ID number

Compound attribute is a set of related attributes

o Example: multiple names for the same customerSheridanSYST30009 - Engineering Quality

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Classes and Objects Domain model class diagram as UML class

o OOA applies domain model class diagram to things

Problem domain objects have attributes Software objects encapsulate attributes and

behaviors o Behavior: action that the object processes itself

Software objects communicate with messages

Information system is a set of interacting objects


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Hierarchies in Class Diagram Notation

Generalization/specialization notationo Inheritance hierarchyo Rank things the more general to the more special

• Motor vehicle class includes trucks, cars, buses

Classification: means of defining classes of thingso Superclass: generalization of a classo Subclass: specialization of a class


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Your Turn…ICE-03 See SLATE


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Class Diagrams – Part IILearning Objectives

Construct a class diagram from a narrative including relationships and multiplicities.

Identify and represent inheritance hierarchies in a class diagram.

Learn what is meant by a concrete and/or abstract class.

How to determine and note the constraints for generalization / specialization relationships.

Learn how to describe Whole-to-Part relationships on a class diagram.

How to draw all these relationships using System Architect.


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Class Diagrams Document the static

structure of the system They define what

classes there are and how they are related

The symbol on the right defines the data and behaviour encapsulated by a class.

Objects “know things and know how to do things!”


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Using System Architect Demo exercise


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Types of Objects From last class…


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Objects- Review We need to know what types of things the user

works with routinely.o Many types

• Tangible• Intangible• Important to include information from all types of users


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Jacobson’s Three TypesOf Objects

• Entity• Interface• Control


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Attributes & Behaviors Attributes Behavior (methods & operations)

o Real worldo Data world


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Class Diagram Showing TwoClasses

Object Diagramwith Two Instances


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Associations/Relationships

relationship among object classes

solid line connecting classes

association is named i.e. drives

where line connects to class is called “association role”


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Associations withMultiplicity

shows number of objects in an association

lower..upper bound bounds are inclusive

2..5 0..1 = optional one 0..* = optional many 1..* = many 1 = exactly one

* *

* *

* *

*

*

The complexity of the Many-to-many relationships

Examples


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Your turn… SLATE – Lesson 08 Class Diagram Exercises


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Subclasses

Some instances of a class (subclass) may be grouped together based on features not shared by the rest of the class.o Attributeso Behavior o Relationships

Key verb is “isakinda” (and inverse, “canbea”).


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Subclasses and Inheritance

A subclass is made up of selected instances from another class, the “Parent class” or “superclass.”

A superclass includes all the instances of the subclass, plus possibly more as well.


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Inheritance is when a subclass instance, in addition to the attributes and behavior it has by virtue of being in the subclass, also has all the attributes and behavior that instances of the superclass have.


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Each subclass then adds

attributes and behaviors

that it needs but the other

one doesn’t.


The subclass relationship actually is a relationship in the way we have used that word.

It requires a verb (one in each direction).o “isakinda”o “canbea”


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isak

inda ca

nbea

Object-Oriented To be considered truly O-O, a language, database,

etc. must support:o Objects,o Classes,o Inheritance, ando Polymorphism


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Subclasses With subclasses, we can show

more detail about relationships on our diagram.o For instance, in most

companies, only managers can hire and fire.

o In other words, only certain kindsa employees can do certain tasks. (only a baker can bake)

We are able to show that some relationships affect only a subclass, not every instance.


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Your turn…

SLATE- Inheritance Exercise


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Generalization, Inheritance & Constraints

generalization path o solid line with hollow

arrowhead pointing from subclass to superclass

indicate basis of generalization

name the path for the attribute being removed = called the discriminator

discriminator shows which property is abstracted by a generalization relationshipSheridan

SYST30009 - Engineering Quality Systems

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Constraints on Generalization

constraints on the subclasses

overlapping: descendent may be descended from more than one of the subclasseso student can be both a

research and teaching assistant

disjoint: descendent may not be descended from more than one of the subclasseso patient can not be both

out and resident


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Constraints on Generalization

complete: all subclasses are listedo only have out and

resident patients incomplete: all

subclasses are not listedo more subclasses are

availableo can have casual, part-

time employees


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Your turn… SLATE – Lesson 5 Vehicle Registration System


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What Comes Next? Continue with relationships

o Class diagram• Whole-Part associations (Aggregation)


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week08. review schedule weeks 8-14 this week o review last class o introduce class diagrams o...

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