Lecture 4

Unified Process Disciplines Phases

Requirements Use case models

UML Use Case Diagrams Class Diagrams Sequence Diagrams Statechart Diagrams

Hat Problem Three persons each one wearing a hat that is

either red or blue with 50% probability. A person can see the colours of the other two

hats but not its own colour. Each player can either make no prediction or

give a guess on the colour of its own hat. The team wins if at least one player guessed

correctly and no player guessed a wrong answer.

There is no form of communication between the players, in particular they do not know which decision any of the other players made.

The players can agree beforehand on a common fixed strategy.

Unified Process

The UP describes work activities, such as writing a use-cas model, within disciplines.

In the UP an artefact, is the general term for any work product, code, diagrams, models, database schema etc. .

There are several disciplines in the UP, business modeling, requirements, design, implementation, test, deployment, configuration and change management.

The course focuses on requirement analysis, design and implementation.

Unified Process

UP Phases Inception: approximate vision, business

case, scope, vague estimates inception = feasibility study Elaboration: refined vision, iterative

implementation of the core architecture, resolution of high risks, identification of most requirements and scope

Construction: iterative implementation of the remaining lower risk and easier elements

Transition: beta tests, deployment

Unified Process

UP disciplines

Inception Elaboration

Construction

Transition

Business modeling

Medium Medium - -

Require-ments

Medium High Low -

Design Low High Medium -

Implemen-tation

- Medium High Medium

Disciplines and phases: relative efforts

Unified Modeling Language

UML a complete language for capturing knowledge (semantics) about a subject and expressing knowledge (syntax) regarding the subject.

Modeling involves a focus on understanding (knowing) a subject (system) and capturing and being able to communicate this knowledge.

UML is the result of unifying the information systems and technology industry´s best engineering practices (principles, techniques, methods and tools)

UML is a notation not a method !!!

Unified Modeling Language

UML is used for specification, visualization and documentation of systems

UML is based on the object oriented paradigm UML applies to a multitude of different types of

systems, domains and methods or processes. UML unifies the syntax and semantics of methods

and tools previously used for object oriented design UML was originally conceived by Rational Software

Corporation and the ”Three Amigos” in 1995 Grady Booch James Rumbaugh Ivar Jacobson

DIA DIA is a diagram creation program from Linkoeping

University http://www.lysator.liu.se/~alla/dia/dia.html

It can be used to draw many different kinds of diagrams Entity relationship diagrams UML diagrams Flowcharts Network diagrams

It is available by adding the module dia module add dia

dia

Use Case Model

Writing use cases is an excellent technique to understand and describe requirements.

A use case is a story of using the system. The Unified Process defines the Use-Case

Model within the requirements discipline. The set of all Use-Cases provides a model of

the system’s functionality and environment.

Use Cases

An actor is something with behavior, such as a person (identified by a role), computer system or organization, for example a cashier.

A scenario is a specific sequence of actions and interactions between actors and the system under investigation, it is also called a use case instance, for example purchasing an item with cash.

A use case is a collection or related scenarios that describe actors using the system to support a goal.

Actors

Actors are classes that define roles that objects external to a system may play. They are used to model users outside of a system that interact directly with the system as part of coherent work units. This includes human users and other systems

Actors are characterized by their external view rather than their internal structure.

Actors participate in interactions involving message exchanges and actions with systems.

Actors have goals to be achieved by interacting with the system.

Use Cases

Uses cases are entities that define units of functionality or behavior provided by the system.

Use cases specify the external requirements of the system and the functionality offered by the system.

Use cases are specified by sequence diagrams representing the external interaction sequences among the systems and its actors.

Use cases are realized, or implemented, by collaboration diagrams representing the internal refinement of the services provided by the system.

Use Cases

When writing use cases you should ask the question: “How can using the system provide observable value to the user or fulfill their goals.”

Use cases describe the functional requirements of a system, that indicate what the system is supposed to do.

Use cases are primarily text documents (written stories) although the may contain UML use case diagrams, to illustrate the names of use cases and actors and their relationship.

Use Cases

Use cases describe the system as having responsibilities, they do not describe the internal workings of the system. They specify what the system must do (functional requirements) not how (design) it will do it.

Incorrect: The system writes the sale to a database.

Instead: The system records the sale.

Use Cases

Formats for use cases Brief : one-paragraph summary,

usually of the main success scenario Casual : multiple paragraphs that

cover various scenarios Fully dressed : elaborate description,

all steps and variations are written in detail, there are supporting sections, such as pre-conditions and success guarantees.

Use Cases

Example (brief format):Borrow book : A library user arrives at the

check-out with books to borrow. The patron identifies herself to the check-out system and the system validates that she is a legitimate user. The patron uses the check-out system to record each borrowed book. The system validates, records each book and associates the book with the patron. The system updates the library inventory. The patron receives a receipt from the system that states the books borrowed and the loan period.

Requirement Analysis

Finding primary actors, goals and use cases Choose the system boundary Identify the primary actors Identify the goals of the actors Define uses cases that satisfy user

goals

Use Cases

Borrow book : Primary actor : patronStakeholders and Interests:

-patron : Wants to borrow and return books quickly and with minimal effort. Wants receipt over borrowed and returned books.

-librarian : Wants system to accurately record transactions. Wants fast access to and automatic update of library inventory.

-library : Wants to reduce operation costs. Wants reliable capture of transactions.

Use Case Diagrams

Use case diagrams render the user view of a system.

Use case diagrams describe the functionality provided by the system or class to external actors.

Use case diagrams contain Actors Use cases Their relationships

Communicates Relationship

Communicates relationships are associations between actors and use cases. They are used to model communications between actors and use cases in which an actor participates, communicates with, or takes part in a use case.

BorrowItems

Return Items

PatronRenewItems

Use Case Diagram

Library system

BorrowItems

Return Items

PatronRenewItems

ManageCatalog

Manage Patrons

Librarian

Borrow Items Use Case

Detailing the functionality of the Borrow Item Use Case

BorrowBook

BorrowPeriodical

Patron

BorrowElectronic Media

Borrow Item

Librarian

Extends Relationships

Extends relationships are generalizations between use cases. They are used to model relationships between use cases in which a base use case instance may include the behavior specified by an extending use case, subject to conditions specified in the extension.

Extends relationships are used to capture exceptional behavior or variations of normal behavior.

Extends Relationships The arrow from the ”Pay by credit card”

use case to the ”Purchase” use case is labeled with an <<extends>> stereotype to indicate that this use case is an option of the ”Purchase Item” use case

PurchaseItem

Pay byCredit card

Customer

<<extends>>

Pay byCheque<<extends>>

Uses Relationships

Uses relationships are generalizations between use cases. They are used to model relationships between use cases in which a base use case instance will also include the behavior specified by a common use case.

Use relationships are used to share common behavior among use cases.

Uses Relationships The arrow from the ”Group Graphics”

and ”Move Graphics” use case to the ”Select Graphics” use case is labeled with an <<uses>> stereotype to indicate that the ”Select Graphics” use case is included in the group and move skills.

Borrow Item

IdentifyPatron

Patron<<uses>>Renew

Items

<<uses>>

Unified Modeling Language

UML object model describes the static structure of the problem domain, it contains Class diagram

describes the class attributes (name and type), operations and the relationship among classes. A class diagram contains classes and associations

Object diagramA class model describes all possible

situation, whereas an object model describes a particular situation. An object diagram contains objects and links which represent the relationship between objects

Unified Modeling Language

The UML dynamic modeldescribes all temporal and dynamic aspects of the system, for example interaction among objects it contains Sequence diagrams describe interactions among classes which are

modeled as exchanges of messages. Sequence diagrams contain class roles, lifelines, activations and messages

Scenariosdescribe interactions among objects

Statechart diagramsdescribe the states and responses of a class. They contain states and transitions.

Domain Model & Design Model

UML class, objects, sequence, statechart diagrams can be used during the OOA/D process for

Domain model : Visual representation of conceptual classes

or real world objects in a domain of interest. A domain model is visualized by a set of

class diagrams Design Model :

Describes how a particular use case is realized in terms of responsibilities and collaborations of objects.

UML Class Diagrams Class diagrams describe the static

structure of a system rather than its behaviour. Class diagrams contain the following elements: Domain objects or conceptual classes

Which represent entities with common characteristics or features.

Attributes of conceptual classes Associations between conceptual classes

Class Diagram

account number balance-------------------------------withdraw(amount) deposit(amount)

Account

Attribute-------------------------------Operation

Class name

Room Booking System

Develop a room reservation system that allows teachers to book lecture halls for their classes.

Each reservation contains information about the room that is booked, the date, start and end time, class, the name of the person who booked the room and a unique booking number.

The reservation system maintains a list of lecture halls including their features such as name, location, size and number.

Class Diagram: Classes & Attributes

number seatsroom numbernamelocation

Room numberstart_timeend_time

Booking

nameposition

Teacher

namecode

Course

• conceptual classes• attributes of conceptual classes

Class Diagram Associations

Room

Booking

Teacher

Class

* *

gets booked by

1

*

teaches

Class Diagram: Associations

RoomBooking1 *

records reservation

teaches

enters

* 1 Teacher

Class

1

*

Multiplicity of Associations

Multiplicitly denotes how many objects of one class are associated with how many objects of the other class. The following symbols can be used to denote the multiplicity of a relationship

1 : exactly one object is involved in the relationship

* : some objects are involved in the relationship

1..* : some objects but at least one 0..* : some objects but possibly zero 0,1 : zero or one object

Multiplicity of Associations

A B1 1 :A :B

Classes Objects:A :B

A B1 *

:A :B

:B

A B* * :A :B

:A :B

:A :B

A B1 0,1 :A :B

:A

:A :B

Association

One object uses another to help it carry out a task.Classes that collaborate are usually related throughassociations. This type of relationship is alsocalled a uses relationship.

string name---------------------...

Personstring modelint number---------------------...

Carowns

1 *

Association Class An association class is a class that

contains information about the relationship among other associated classes.

date loan_dateint loan_periodbool returned---------------------...

Loan

string titleint isbnnumber---------------------...

Bookborrows

* *string nameint libraryid---------------------...

Person

Association Classes

Part

Customerbuys from

*

*Supplier

customer number

partnumber

supplies

*buys

quantity / date

*

*

Higher Order Associations

PartCustomer

1Supplier

Order----------------------------

quantity

*1

Part Customer

1Supplier

quantity /date

*

Order1

**

*

Multiple Associations Sometimes two classes are associated

with each other in more than one way

int sizestring namelong index---------------------...

Fileaccesses

* *

string nameint uid---------------------...

Userowns

1 *

Self-Associations Sometimes a class is associated to itself

as different objects play different roles

string namestring address---------------------...

Companyworks for

*

1

string namestring position---------------------...

Employee

manager

subordinate

*

1

Navigability An association can indicate the

responsibility of the involved objects by an arrow that indicates the direction of the association. If navigability exists only in one direction we call the association uni-directional otherwise bidirectional.

string name---------------------...

Person

string type---------------------...

Carsowns

1 *

Aggregation

Aggregation means that one object contains other objects. Aggregation is also called part-of relationship.

Addressbook Persons* *

class Person{ string name; ...}

class Addressbook{ Person[] persons; ... }

Aggregation

Document Paragraph Lines

Figures

1 * 1 *1

*

class Line

{ string text; ...}

class Paragraph

{ Line[] lines; ... }

class Figure { ...}

class Document

{ Paragraph[] paragraphs;

Figure[] figures; }

CompositionComposition is building objects from parts.

It is stronge type of aggregation in which the parts are necessary to the whole, namely they are permanently bound to the object and do not exist outside the object. Composition is ”is build of” relationship

Processor

CPU

1

1

Memory I/O Port

1 1

Generalization

Generalization is a relationship defined at the class level not the object level, which means that all objects of this class must obey the relationship. This is type of relationship is also called a is-a-kind-of relationship.

Vehicle

Car Truck Motor Cycle

class Vehicle:

class Car : public Vehicle

class Truck : public Vehicle

class MotorCycle : public Vehicle

Sequence Diagrams

Sequence diagrams describe interactions among classes. These interactions are modeled as exchanges of messages.

Sequence diagrams focus on classes and the messages they exchange to accomplish some desired behavior.

Sequence Diagrams

Sequence diagrams are a type of interaction diagrams that contain Class roles represent roles that

objects may play within the interaction.

Lifelines represent the existence of an object over a period of time.

Activations represent the time during which an object is performing an operation.

Messages represent communications between objects.

Sequence Diagram

The interaction diagram illustrates the essential steps of playing, by sending messages to the instances of the DiceGame and Die classes.:DiceGame

roll()

die 1 : Die die2 : Die

fv1:=getFaceValue()

play()

roll()

fv2:=getFaceValue()

Observer Sequence Diagram

ConcreteSubjectObject

ConcreteObserverObjectA

ConcreteObserverObjectB

Notify()

SetState()

Update()

GetState()

Update()

GetState()

time

class role

message

activation

lifeline

Observer Sequence Diagram

EventHandler

SelectGraphics()

Draw()

UserWindowManager

MoveGraphics()

Draw()

UML Statechart Diagrams

Statechart diagrams lie within the behavioral view of a system and render the states and responses of a class.

Statechart diagrams describe the behaviour of a class in response to external stimuli.

Statechart diagrams describe the life cycle of an object.

Statechart diagrams contain States Transitions

Finite State Machines (FSM)

States An FSM is exactly in one current state. An FSM has an initial state. An FSM may change state due to a

transition. Transitions

Transitions connect states with each other.

Transitions carry a label or a guard condition that triggers the transition.

Transitions can be defined by a transition matrix.

FSM Example

States : A,B,C, A is initial state Labels : 0,1 Transitions:

(A,0) -> B, (A,1) ->C, (B,0)-> B (B,1) -> C, (C,0) ->C, (C,1)-> B

A

B

C

0

1

0

0

11

FSM Example

Input sequence: 011010 State sequence: A-B-C-B-B-C-C State B: even number of 1’s in

sequence State C: odd number of 1’s in sequence

A

B

C

0

1

0

0

11

Statechart Diagrams

States are classes that define status conditions that an object may satisfy during its existence.

States are used to model the situations during the life of an entity in which it satisfies some condition, performs some activity, or waits for some occurence.

An entity remains in a state for a finite and non-instantaneous time.

Statechart Diagrams

Transitions are associations between states. They are used to model relationships between the different states of an entity.

An entity in one state will perform actions and possibly enter another state when an event occurs and a condition is satisfied (if specified), this occurence is known as the firing of a transition.

Statechart Diagrams

Transitions are denoted as solid arrows between states and are labeled with a transition symbol.

Transitions relate source state and target state vertices.

Transitions may have square brackets containing a boolean guard condition that must be satisfied in order to enable the transition to fire.

Transitions may have a forward slash followed by one or more actions that result when the transition fires.

Statechart Diagram

Source State

Target State

Event [Guard] / Action

Example Statechart Diagram

NotSelected

Selected

transition

creation

click event [inside object] / add to selected graphics

click event[outside object and not shift key] / delete from selected graphics

click event [shift key pressed]

initial pseudo state

guard

action

state

Hat Problem

Simple strategy: Player A always guesses colour red, the other players make no guess. Probability of winning is 50%.

Common strategy: Players agree that when a player sees two hats with identical colours, then he guesses the opposite colour, if he sees two different colours he makes no guess. Chance of winning as a team is 75%

25% RRR, BBB: all three players guess wrong 75% RRB, RBR, RBB, BRB, BBR, BRR : one

player guesses correctly, the other two players make no guess