UML and Systems Analysis

MIS3502: Application Integration and Evaluation

Paul Weinberg

weinberg@temple.edu

Presentation by David Schuff and Paul Weinberg

Review: What is Systems Analysis and Design?

Systems Analysis Analysis of complex, large-scale

systems and the interactions within those systemshttp://en.wikipedia.org/wiki/Systems_analysis

Systems Design The process of defining the hardware

and software architectures, components, models, interfaces, and data for a computer system to satisfy specified requirementshttp://en.wikipedia.org/wiki/Systems_design

Notice that they are not the same!

Basically…

Systems Analysis is the process of modeling the problemRequirements-oriented What should we do?

Systems Design is the process of modeling a solutionFunctionality-orientedHow should we do it?

Why model?

Creating a blueprint for an application Before you start coding The idea is to minimize having to go

back and make changes later

Why consider SAD in a programming course?

The business analysts

The development

team

Analysis Design Development

What this means

A developer must be able to turn the design into code

But a good analyst should be able to understand all parts of system developmentConduct an analysisDevelop a designImplement the design (coding)

Example: Bjork’s ATM example

An Example of Object Oriented Design, An ATM Simulation, Russell Bjork http://www.math-cs.gordon.edu/local/courses/cs211/

ATMExample/

What we’ll look at…

Use case diagrams

Use case descriptionsActivity diagrams

:Controller :Customer :Order

Interaction diagrams

Analysis Models Design Models

Class name

Attributes

Operations

Customer

name

findName()

Design class diagrams

All diagrams adapted from “Systems Analysis and Design in a Changing World”, 3rd EditionSatzinger, Jackson, Burd, Thompson Publishing, 2004.

Problem Statement

What is the application supposed to accomplish? Use words, not code Be as descriptive as possible Potential sources of information

Forms, reports Engineering drawings Real world object specifications Interviews

Problem statement for ATM application

Services one customer at a time Must be able to handle 10 customers an hour Customer inserts ATM card and enters PIN to begin Transactions

Cash withdrawals --- in $20 increments Deposits Transfers Balance inquiries

Immediate transaction validation with the bank Standard error procedures

Pin error, rejection due to inadequate balance Reports

Use Case Diagram

Use case: sequence of events that represents an interaction between the user and the system

CashWithdrawal

Deposit

Transfer

Invalid PIN

Session

Partial list of use cases from Bjork

example

Customer(actor)

Bank(actor)

Narrative Problem Statement - Use Cases A use case is a logical sequence of events from the

users first interaction, to the desired outcome.

For each use scenario, and each user (actor) . . . a use case describes The services the system provides to the user The sequence of events The desired outcome

Users of systems can be people organizations other systems

A Use Case for the ATM

From the Bjork website:System startup . . .

User: System operatorServices: Load cash dispenser, start ATM

"The system is started when the operatorturns the switch on the panel to 'on'. The operator will be asked to enter the amount

of money in the cash dispenser . . . "

Object Classes Are . . .

Tangible Things Airplane, ATM, person

Roles Professor, student

Incidents and interactions Purchase, withdrawal, flight

Specifications Aircraft characteristics: Weight, wingspan, max

speed

Notice that many objects are not physical. (e.g. transactions, like a purchase, are not physical)

Identifying Potential Object Classes

Identify noun-phrases (nouns and related adjectives) in the narrative descriptions

Eliminate duplicates (including plurals of items in the list) Eliminate state information (e.g. terms like "completion") Eliminate synonyms Assure that the classes are abstractions that a user would

recognize (Not implementation tools) Determine whether actors not in the class list should be. Check to

see if other actors need their services.

Naming Objects

Avoid roles or states in the names (e.g. ATM dispensing cash)

Testing Potential Classes

Objects instantiated from the classes must have the same set of attributes . . . Dog licenses and vehicle licenses cannot be in the same

class However, they can both be derived from the same class

Objects must have attributes Social security number is not a class, it is only a name Social security account is a class

"Or" must be avoided in defining the class The objects formed from a class must be more than a

list . . . The class must be definable

Static Class Relationships

Static relationships Inheritance: Class a is derived from class b Association, e.g.

President runs an airline

There are many students in one University

There may be many Universities associated with one student.

Aggregation (Special case of association): class a "is comprised of" Class b, e.g.

A building has rooms

A course has 5 sections

Associations and aggregations are coded the same way.

Static Class Relationships in the Unified Modeling Language (UML)

Animal

Dog Cat

Inheritance

School

University

Aggregation

Static Class Relationships in the Unified Modeling Language (UML) - Continued

Section Professor

Course *

*

1

*

1*

Association relationships possible: 1 * --- One to many* * --- Many to many1 1 --- One to one

What are the specific associations in this example?

Associations

Static Class Relationships in the Unified Modeling Language (UML) - Continued

Section Professor

Course *

*

1

*

1*

PersonInheritance and

Associations in thesame diagram

Exercise Consider the following list of ATM classes

Are there any inheritance relationships? Do any classes contain other classes? Are there any other associations --- what are they?

Bank

Card Reader Session

Keyboard Transaction

Display Withdrawal

Cash Dispenser Envelope Acceptor

Operator Panel Deposit

Transfer Inquiry

Draw a UML representation of the relationships.Review: Bjork's UML definition.

Completing the Static Class Definitions

Determine and define attributes of each class

Give an example of a field belonging to thecash dispenser.

Dynamic class behavior (public methods)

State of an object --- Values of all attributes at a specific time

Methods --- Respond to events Handle requests from other objects Send requests to other objects by calling

their methods May return values --- Accessor methods (i.e.

have a non-void return value) May modify state of an object --- Mutator

methods (i.e. may have a void return value)

A first step in establishing public methods Start with a use case or state diagram Construct a sequence of steps required of

objects to complete the sequence of events associated with each use case.

For each step Service description Object requesting the service (client) Object fulfilling the service Next object (or objects) involved in

completing the sequence Identify methods for each object to perform the

services.

Sequence of Steps for a Withdrawal

Withdrawal transaction ATM --> Card Reader checkForCardInserted() ATM --> Session startSession() Session --> Keyboard readPin() Session --> Keyboard readMenuChoice() Session --> WithDrawalTransaction

getTransactionSpecifics() WithDrawalTransaction --> Bank initiateWithdrawal

(cardNumber,PIN,ATM number, serial, from, amount)

Some of these steps require instantiation of newobjects by adding them to ArrayLists . . . others do not.

What is an example of this?Following the state diagram for a session, what's next?

Next step: From model to program . . . Inheritance relationships coded as : Relationships

1:1 becomes instantiation of the related class 1:* becomes instantiation of a ArrayList or array

containing the related class Public Methods are determined from each sequence

of steps for major uses. The methods are associated with specific classes. Additional implementation classes

GUI design and classes Data base and other technology-related classes

Design class diagrams

Shows the attributes and methods of each class

Get the object names and attributes from the noun-phrase analysis What is the object?

Get the methods from the activity diagram What should it do?

Class DepositTransaction

toAccountAmount

DepositTransaction(session, atm, bank)getTransactionSpecificsFromCustomer()sendToBank()finishApprovedTransaction()

Activity diagram

Show which activities occur during a use case

This is for the deposit use caseThe

customer initiates the transaction

Customer ATM

Choose depositAsk which type

of account

Choose accounttype

Send customerinformation to bank

Bank

Incorrect PIN?

Credit customeraccount

Transactioncompleted

Incorrect PINexception

Transactionfailed

Approvetransaction

yes no

yesno

Ask deposit amount

Choose depositamount

Working from the design class diagram

The DepositTransaction class will have Two attributes Four methods

We can tell from this what methods the class will have but not what they do Refer to the use cases,

activity diagrams, and interaction diagrams for detail

Class DepositTransaction

toAccountAmount

DepositTransaction(session, atm, bank)getTransactionSpecificsFromCustomer()sendToBank()finishApprovedTransaction()

Interaction Diagrams

Show how the objects in the application “use” each other

Which methods are called What data is returned

ATM application:Deposit Use Case

:Session :Bank

DepositTransaction(session, atm, bank)

sendToBank()

(approval)

finishApprovedTransaction()

(confirmation)

checkIfCashAvailable(amount)

(confirmation)

initiateDeposit(account, amount)

(confirmation)

:DepositTransaction

(self)getTransactionSpecificsFromCustomer()

Session(session, atm, bank)

:ATM

Customer

Fitting everything together

CashWithdrawal

Deposit

Transfer

Invalid PIN

Session

Customer(actor)

Bank(actor) A deposit transaction is started from within a session when the customer chooses

deposit from the menu of possible transaction types. The customer chooses a type of account to deposit to (e.g. checking) from a menu of possible accounts, and then chooses a dollar amount by typing it on the keyboard. The system sends the customer's card number, PIN, chosen account and amount to the bank, which either approves or disapproves the transaction. If the transaction is approved, the machine accepts an envelope from the customer containing cash and/or checks and then issues a receipt. (If the customer does not insert the envelope within a specified period of time, this operation times out and the deposit transaction is aborted.) If the transaction is disapproved due to an incorrect PIN, the Incorrect PIN extension is executed. All other disapprovals are reported to the session, which initiates the Failed Transaction Extension. The bank is notified whether or not an approved transaction was completed in its entirety by the machine; if it is completed then the bank completes crediting the customer's account for the amount - contingent on manual verification of the deposit envelope contents by an operator later.

Customer ATM

Choose depositAsk which type

of account

Choose accounttype

Send customerinformation to bank

Bank

Incorrect PIN?

Credit customeraccount

Transactioncompleted

Incorrect PINexception

Transactionfailed

Approvetransaction

yes no

yesno

DepositTransaction(session, atm, bank)

getTransactionSpecificsFromCustomer()

sendToBank()

finishApprovedTransaction()

toAccount

Amount

Class DepositTransaction

DepositTransaction(session, atm, bank)

getTransactionSpecificsFromCustomer()

sendToBank()

finishApprovedTransaction()

toAccount

Amount

Class DepositTransaction:Session :Bank

DepositTransaction(session, atm, bank)

sendToBank()

(approval)

finishApprovedTransaction()

(confirmation)

checkIfCashAvailable(amount)

(confirmation)

initiateDeposit(account, amount)

(confirmation)

:DepositTransaction

Session(session, atm, bank)

:ATM

Customer

Use case diagram

List of all use cases in the application

Use case diagram

List of all use cases in the application

Use case descriptions

Textual description of what happens in

each use case

Use case descriptions

Textual description of what happens in

each use case

Activity diagram

Picture of the activities

described in each use case

Activity diagram

Picture of the activities

described in each use case

Design class diagrams

List of all methods and attributes in

each object

Design class diagrams

List of all methods and attributes in

each object

Interaction diagram

Diagram of how the objects work

together for each use case

Interaction diagram

Diagram of how the objects work

together for each use case

Scenarios Objects

Integration and UML: Web Services

We’ll be working with this application later in the course

It uses the MSN Live Search web service to search the web

Microsoft’s web service is a distributed object

Things to think about

What if you have to code something not accounted for in the design diagrams?

Does the diagram have to match the code exactly?

What does it mean when……additional detail is required?…specified methods go unused? …different sequencing is required?