lecture 1

Currently:

-Software projects costs are going up and hardware costs are going down

-Software development time is getting longer and maintenance costs are getting higher

-Software error getting more frequent while hardware errors becomes almost rare.

- Software is developed using a rigid structured process that is inflexible.

Software project costs by development phase

Work step %

Requirements 3Design 8Programming 7Testing 15Maintenance 67

Modern Corporations are headed toward disaster

Any corporation decisions based on the output of incorrect software can threaten theability of a business to be financially strong tomorrow

Projects

Success 16.2%

Challenged 52.7%

Impaired 31.1%

Successful projects deliver full functionalityon-time and on-budget

Challenged projects deliver, but less than full functionality, over-budget, and late

Impaired are cancelled during development

Many projects are started with the wrong goals and find themselves having to start over again from the beginning.

Starting over does not support delivering at the original deliver date.

Standish Group found that for every 100 Projects that start, there are 94 restarts.

Approximately 28% of projects exhibit costoverruns of 150% to 200% of their original cost estimate.

A common joke about delivering software:

Do you want it on time or fully functional

What does the customer want

A customer wants a solution that:

Meets functional requirements

Adapts to the rapidly changing business environment.

Fits the run time (time/Space) constrains

A customer wants a software that is:

Maintainable Developed within budgeted resources ( time/ space / people ) Designed with appropriate longevity in mind

Classical

Object-Oriented

Development(structured, data modeling, ad hoc, etc )

AN OVERVIEW OF

METHODOLOGIES

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15

Planning & Feasibility Study (optional)

Analysis - Requirements Determination

Design - Conceptual &

Physical

Construction (Purchase) & Testing

Implementation including Training &

Conversion

Evolution - Maintenance &

Enhancements

SYSTEMS DEVELOPMENT LIFE CYCLE (SDLC)

System Life Cycle – Why?

• Need an agreed framework for the development– Identify milestones– Structure activities– Monitoring deliverables

System Life Cycle – Why?

• Advantages of agreed framework– An overall picture of the development process– A basis for development – Consistency in approach – Ensures quality

• Structure for planning, monitoring and controlling the development process

Problems with Traditional Approach

• Functional Decomposition– Functions and data separated– Data accessible by several processes

Major problem - data not protected

• Poor modularity• Data versus function

Problems with Traditional Approach

• Functional Decomposition• Poor modularity

– Ideally modules should be self-contained– Have well defined purpose– Be independent

Major problem – interdependency between modules

• Data versus function

METHODOLOGY OVERVIEW

• Methodology defined: The way something gets done. (i.e., The strategy, steps, directions, or actions.)

• Methodologies can be:• purchased• created• combination of both

• Thousands available for developing software-intensive information systems

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SDLC versus Methodology

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M #1 M #2…

SDLC =“GenericWay”

Methodology =“Specific Ways”

METHODOLOGY OVERVIEW

• Classifications of Methodologies• Traditional• Structured Analysis and Design• Information Modeling/Engineering• Object-Oriented

• Prototyping is a technique - (some say that it is a methodology)

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The Traditional Methodology

• Applicable for small teams on small projects

• Functional perspective of a problem domain

• It is an informal, unstructured, unrepeatable, un-

measurable, ad-hoc way

• Tools used to support it are adequate (okay)23

(1950s - now)

Traditional Methodology Tools

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-----------TECHNIQUES & TOOLS REPRESENTING-----------System Data ProcessFlows Logic _

Forms,

Layouts,

Grid Charts

System

Flowcharts

English Narrative,

Playscript,

Program Flowcharts,

HIPO Charts

Structured Analysis and Design Methodology

• Data Flow methodology (synonym)

• Compliments Structured Programming

• Very popular - perhaps the leading one for business

• Can be repeatable, measurable, & automated

• IDE & CASE s/w tools brought significant assistance

• 1) Yourdon, and 2) Gane & Sarson

• Functional perspective of a problem domain

• Describes the real world as data flowing through the information system, being transformed from inputs to outputs

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(mid-1970s - now)

Structured Analysis and Design Methodology Tools

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Data Dictionary,

Data Structure

Diagrams,

Entity-

Relationship

Diagrams

Data Flow

DiagramDecision Tree/Table,

Structured English,

Structure Charts,

Warnier/Orr Diagram

Reconcile Account Balances

Pay a

Bill

Withdraw Funds from an Account

Deposit Funds into an Account

Bank

Creditor

Employer

Other Income Source

Bank

Monthly Account Statements

Account Transactions

Bank Accounts

Account Transactions

Bill

Payment

Monthly Statement

Account Balance

Transaction

Prior Monthly Statement

New or Modified Monthly Statement

Modified Balance

Pay

Reimbursement

Withdraw or transfer

Deposit

Payment

Modified Balance

Current Balance

(adapted from Systems Analysis andDesign Methods, 4th Edition, Whittenand Bentley, McGraw-Hill, 1998)

(adapted from Systems Analysis andDesign Methods, 4th Edition, Whittenand Bentley, McGraw-Hill, 1998)

CUSTOMER

Customer Number (PK) Customer Name Shipping Address Billing Address Balance Due

ORDER

Order Number (PK) Order Date Order Total Cost Customer Number (FK)

INVENTORY PRODUCT

Product Number (PK) Product Name Product Unit of Measure Product Unit Price

ORDERED PRODUCT

Ordered Product ID (PK) . Order Number (FK) . Product Number (FK) Quantity Ordered Unit Price at Time of Order

has placed

sold

sold as

Information Modeling Methodology

• Data modeling & information engineering

(synonyms)

• Describes the real world by its data, the data’s

attributes, and the data relationships

• Can be repeatable, measurable, and automated

• Data perspective of the problem domain

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(early-1980s - now)

Information Modeling Methodology Tools

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Business

Area

Analysis,

Entity-

Relationship

Diagrams

Business

Area

Analysis,

Process

Model

Business Systems

Design

Object-Oriented Methodology

• Object modeling

• Compliments object-oriented programming

• Can be repeatable, measurable, & automated

• Object perspective of the problem domain

• Describes the real world by its objects, the attributes,

operations, and relationships

• Data & functions are encapsulated together

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(mid/late-1980s - now)

Object-OrientedMethodology Tools

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Object Model

Attributes

Object

Model

Static & Dynamic UML

Model Diagrams,

Operations,

Class relationships,

Object associations

Object-Oriented Methodology

• Revolutionary or Evolutionary?

• Most difficult aspect is the transition some people have

to make from a functional or data problem solving

strategy to an object problem solving strategy. Some

people must change from a “function think” or “data

think” to an “object think” strategy.

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The Object-Orientated Approach

Phases (stages) of Development

• Inception• Elaboration• Construction• Transition

These indicate the state of the system at each phase NOT the activities involved at that point in

development



1. Inception – the initial work required to set up and agree terms for the project.

Includes establishing the business case

– Feasibility

– Basic risk assessment

– Scope of the system to be delivered



1. Inception

2. Elaboration – deals with putting the basic architecture of the system in place

– All main project risks are identified

3. Construction

4. Transition



1. Inception

2. Elaboration

3. Construction – involves bulk of work on building the system

– Ends with beta-release of system

4. Transition



1. Inception

2 Elaboration

3 Construction

4 Transition – process involved in transferring the system to the clients and users

Workflows• The activities implied by the stages in a traditional

structured modelling approach are referred to as Workflows in the object-orientated approach

• Workflows -– Requirements– Analysis– Design– Implementation– Testing

Workflows - activities

Inception

Elaboration

Construction

Transition

Requirements

Analysis

Design

Implementation

PHASES WORKFLOWS


Iterative Process - • Workflows may be carried out during any

phase of development• In each phase a range of workflows (activities)

may be carried out several times before moving on to the next phase


A range of workflows (activities) take place during the development of a system

Requirements

Analysis

Design

Implementation

Testing


I n c e p t i o n

E l a b o r a t i o n

C o n s t r u c t i o n

T r a n s i t i o n

An iterative process.

The ellipses represent iterations of workflows (requirements, analysis, design, implementation, testing)

A seamless Development Process• Phases less distinct than in a structured

approach• Difficult to say when one phase ends and

another begins• Driven by a single unifying idea – the object


The Object

• Basic building block• Objects in the real world translate into objects

in the software system– Physical (customers, products)– Conceptual (orders, reservations)– Organisation (companies, departments)– Implementation (GUI Windows)

• The foundation of all development work is the object

• No new system models introduced at different stages

• Early models developed and refined through the development process

• An iterative design process


Why OOP?/ Benefits•MaintainableOOP methods make code more maintainable. Identifying the source of errors becomes easier because objects are self-contained (encapsulation). The principles of good OOP design contribute to an application’s maintainability.•ReusableBecause objects contain both data and functions that act on data, objects can be thought of as self-contained “boxes” (encapsulation).

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• This feature makes it easy to reuse code in new systems. Messages provide a predefined interface to an object’s data and functionality.

• OOP languages, such as C# and VB.Net, make it easy to expand on the functionality of these “boxes” (polymorphism and inheritance), even if you don’t know much about their implementation (again, encapsulation).

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• ScalableOO applications are more scalable then their structured programming roots.

• As an object’s interface provides a roadmap for reusing the object in new software, it also provides you with all the information you need to replace the object without affecting other code.

• This makes it easy to replace old and aging code with faster algorithms and newertechnology.

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• Some DisadvantagesThe challenges of OOP exists mainly in the conversion of legacy systems that are built in structured programming languages.

• The technical challenge is not as big as the actual design challenge.

• The goal when converting is to minimize the effects of the structural systems on the OO nature of the new design, and this can sometimes be difficult.

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Object Technology Principles

Common Methods of Organization

Abstraction

Encapsulation (Information Hiding)

Inheritance

Polymorphism

Message Communication

Associations

Reuse 51

• Objects and their characteristics

• Wholes and Parts

• Groups (Classes) and Members

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Classification Theory(Common Methods of Organization)

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• Common Methods of Organization

People are accustomed to thinking in terms

of...

• color• price• weight• engine• options...

Objects & Attributes

• number of doors• number of wheels• number of windows• number of lights• number of bolt type 1• number of bolt type 2• etc....

Wholes and PartsGroups & Members

VANS:• light utility• utility• passenger• etc...

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• AbstractionA mental ability that permits people to view real-world

problem domains with varying degrees of detail depending on the current context of the problem.

• Helps people to think about what they are doing• Functional and Data abstraction

In Object-Oriented Technology the “package” is called an OBJECT The interface to each object is defined in such a way as to reveal as little as possible

about its inner workings Encapsulation allows [software] changes to be reliably made with limited effort

[Gannon, Hamlet, & Mills, 1987]

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• Encapsulation (Information Hiding)

A technique in which data are packaged

together with their corresponding procedures.

cakeIngredients

Directions

2 eggs 4 cups flour1 cup milk 1 cup sugaretc.......

Pre-heat oven to 350; Putmilk, eggs, and sugarin 2 quart mixing bowl...

One cake please!

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• InheritanceA mechanism for expressing similarity

between things thus simplifying their

definition.

• looks• behavior• attitudes• etc...

Person

Student Faculty Staff

Inheritance

• H O = water, ice, steam (liquid, solid, vapor)• Eating• Carbon compound crystallizes as graphite & diamond

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• Polymorphism (“many forms”)

The ability to hide different implementations

behind a common interface.

The ability for two or more objects to respond

to the same request, each in its own way.

2

versusDoor#1

Door#2

Door#3

Door#1#2#3

• Polymorphism Two examples

PRINT

0

5000

10000

15000

20000

25000

30000

North South East West

B L U E S K Y AI R L I N E S SalesReport January

B L U E S K Y AI R L I N E S SalesReport February

PRINT

PRINT

TEXT object

GRAPH object

IMAGE object

Object #1 PO object

Account object

Department object

Object #2

Object #3

Add

Add

Add

= add a line item to the PO

= increase $ Amount Balance

= hire a new employee

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• Message Communication

OBJECT

OBJECT

OBJECT

OBJECT

Objects communicate via messages

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• AssociationsThe union or connection of ideas or things.

(Objects need to interact with each other)

• same point in time

Billing StatementAdvertisement #1Advertisement #2

• under similar circumstances

crimescene

#1

crimescene

#2

crimescene

#n

Person

Student Faculty Staff

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• Reuse

Varying Degrees of Reuse:

• complete or sharing

• copy, purchase or cloning

• partial or adjusting

• none

The ability to reuse objects

Software:• “Chips”• Components• Controls• Models

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• Reuse

• Components must be reused three to five times before the costs of creating and supporting them are recovered• It costs one and a half to three times as much to create and support a single reusable component as to create a component for just one use• It costs 25% as much to use a reusable component as it does to create a new one• It takes two to three product cycles (about three years) before the benefits of reuse become significant

Software Reuse Costs and PayoffsOrenstein, D. “Code reuse: Reality doesn’t match promise”,

Computerworld, August 24, 1998, page 8.

O-O Systems Analysis & Design Methodology

• Data Model versus Function Model

• Analysis to Design Transition

• Maintaining Source Code

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Three Classic Systems Analysis and Design Challenges:

VVVVVVVVVVVV

Colorado River

North Rim of theGrand Canyon

South Rim of theGrand Canyon

Classic Software Development Challenge #1:Multiple Models

DataModels

FunctionModels

User InteractionUser Interaction(Behavior)(Behavior)

VVVVVVVVVVVV

Colorado River

North Rim of theGrand Canyon

South Rim of theGrand Canyon

Classic Software Development Challenge #2:Model Transformation

DesignModels

AnalysisModels

Classic Software Development Challenge #3:Maintaining Source Code

Begin “Caller” Program Init x,y,z... Open (files/database) Read... Compute...

DO “Callee” with x,y,z

Update (files/database) Close (files/database) End Main Program

Procedure Callee Parameters x,y,z Compute... End Procedure

End Program

Spaghetti?

Who wrotethis code?

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SOLUTION

Colorado River

ObjectTechnology

INTEGRATED MODEL(S)(function, data, behavior)

(analysis, design and implementation)

ROUND-TRIPENGINEERING

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A SimplifiedObject-Oriented

Systems AnalysisMethodology

O-O Systems Analysis Methodology

1. Identify the information system’s purpose

2. Identify the information system’s actors and features

3. Identify Use Cases and create a Use Case Diagram

4. Identify Objects and their Classes and create a Class Diagram

5. Create Interaction/Scenario Diagrams

6. Create Detail Logic for Operations

7. Repeat activities 1-6 as required to refine the “blueprints”

A Simplified Object-Oriented Systems Analysis Methodology

Activities

Software Development’s “Separation of Concerns”

Problem Domain

Data Management System Interaction

Information System

Human Interaction

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The Unified Modeling Language (UML)

Models and Notation

O-O Systems Analysis O-O Systems Analysis MethodologyMethodology

Subject Matter Expert & Notation

• Can you draw a stick figure of a person?

• Can you draw a picture of an automobile?

• Can you draw a picture of the space shuttle?

• Can you draw a picture of an Oopsla?

• Why not?

• Subject Matter Expert (SME)

• Notation - symbols used to communicate

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Booch Jacobson Rumbaugh

“The 3 Amigos”

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Information Systems Development

People Process

Technology(UML - notation & tools to use it)

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The Object Management Group (OMG), formed in

1989, is a consortium of about 800 software

vendors, consultants and end user organizations

whose mission is to develop STANDARD interfaces

for INTEROPERABLE software components in

HETEROGENEOUS computing environments.

Version 1.1 of the UML was adopted as an OMG Standard on November 14, 1997

www.omg.org

The OMG Revision Task Force released UML Version 1.3 in the Fall of 1998

Unified Modelling Language - UML

• A notation or language for development• Not a development method• Set of diagrammatic techniques• Industry standard for modelling OO systems• UML Creators – Ivar Jacobson, Grady Booch, James

Rumbaugh

Principal UML ModelsModel View of the system

Use case How the system interacts with its users.

Class The data elements in the system and the relationships between them.

Interaction (sequence and collaboration)

How a use case affects all the objects that are involved in it.

State How the different objects of a single class behave through all the use cases in which the class in involved.

Activity The sequence of activities that make up a process.

Component The different components of the system and the dependencies between them.

Deployment The software and hardware elements of the system and the physical relationships between them.

The UML Provides Standardized Diagrams

DeploymentDiagram

DeploymentDiagram

Use CaseDiagrams

Use CaseDiagramsUse Case

Diagrams


Diagrams

Use CaseDiagrams

ScenarioDiagrams

ScenarioDiagramsScenario

Diagrams

ScenarioDiagramsSequence

Diagrams

SequenceDiagrams

StateDiagrams

StateDiagramsState

Diagrams

StateDiagramsState

Diagrams

StateDiagrams

ComponentDiagrams

ComponentDiagramsComponent

Diagrams

ComponentDiagramsComponentDiagrams

ComponentDiagrams

Model

StateDiagrams

StateDiagramsState

Diagrams

StateDiagramsObject

Diagrams

ObjectDiagrams

ScenarioDiagrams

ScenarioDiagramsScenario

Diagrams

ScenarioDiagramsCollaboration

Diagrams

CollaborationDiagrams

Use CaseDiagrams


Diagrams

Use CaseDiagramsActivity

Diagrams

ActivityDiagrams

StateDiagrams

StateDiagramsState

Diagrams

StateDiagramsClass

Diagrams

ClassDiagrams

Unified Modeling Language (UML)

“A graphical language for visualizing, specifying, constructing, and documenting the artifacts of a software intensive system.” [Booch]

UML in One Sentence

The UML is a graphical language for• visualizing• specifying• constructing• documentingartifacts of a software-intensive system.

Visualizing

• explicit model facilitates communication• some structures transcend (pass or more) what

can be represented in programming language• each symbol has well-defined semantics behind it

Specifying

The UML addresses the specification of all important analysis, design, and implementation decisions.

Constructing

• Forward engineering: generation of code from model into programming language

• Reverse engineering: reconstructing model from implementation

• Round-trip engineering: going both ways

UML and Blueprints

The UML provides a standard way to write a system’s “blueprints” to account for

• conceptual things (business processes, system functions)

• concrete things (C++/Java classes, database schemas, reusable software components)

In UML, we have a state diagram for dynamic behavior. The state diagram shows:

-State-Transition-Event-Condition-Action

Construct Description Syntax

class a description of a set of objects that share the same attributes, operations, methods, relationships and semantics.

interface a named set of operations that characterize the behavior of an element.

component a modular, replaceable and significant part of a system that packages implementation and exposes a set of interfaces.

node a run-time physical object that represents a computational resource.

«interface»

Structural Modeling: Core Elements

Structural Modeling: Core Elements (Continued)


constraint a semantic condition or restriction.

{constra in t}

package orsubsystem

a holder for grouping elements


association a relationship between two or more classifiers that involves connections among their instances.

aggregation A special form of association that specifies a whole-part relationship between the aggregate (whole) and the component part.

generalization a taxonomic relationship between a more general and a more specific element.

dependency a relationship between two modeling elements, in which a change to one modeling element (the independent element) will affect the other modeling element (the dependent element).

Structural Modeling: Core Relationships

(open arrow)

Composition


realization a relationship between a specification and its implementation.

Structural Modeling: Core Relationships (Continued)

(closed arrow)

Realization relationship connects a model element such as a class, to another model element, such as an interface that supplies its behavioral specification but not its structure or implementation. The client must support ( by inheritance or by direct declaration) at least all the operations that the supplier has.

Class Diagram Concepts

• A static model that shows the classes and relationships among classes that remain constant in the system over time

Class Diagram for Manage Appointment

HW1: due date one week from today:Model the following using a class diagram:Your company writes student and course data management software for universities. You are writing a data management package for a university with several campuses. Employees in the administration office of each campus has to enter several student and class input parameters; these will be stored in a central database in the main campus. CORBA has been chosen to send this data. There will be two kinds of data: per student data, and per course data. For each student, the administration employee will enter a social security number, a 3 line home address, and the current semester’s grades (the student will have taken at least one class, and no more than 5 classes). If the student is also a university employee, the administration employee will enter the student’s salary. For each course, the administration employee will enter the instructor’s name, the time of day the course meets, the days of the week the course meets, the date and time of the final exam, and the number of hours of the course. The administration employee will also enter a student name and social security number for each student in the course.The central database software will provide values in return. For each student, the student’s new GPA (based on existing plus new classes) will be returned, along with total number of courses the student has taken at the university. For each course, the central database software will provide the total number of courses the instructor is teaching this semester. If the final exam time entered does not match that stored in the central database, then the final exam time variable will be corrected

The 9 Diagrams of the UML ClassClass ObjectObject Use-CaseUse-Case Interaction/Scenario Diagrams:Interaction/Scenario Diagrams:

– SequenceSequence

– CollaborationCollaboration

State [-Transition]State [-Transition] ActivityActivity ComponentComponent DeploymentDeployment

Implementation(Static)

Behavior

Static

A Package is used for Model Management

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UML

Diagrams

103

“The Big Picture”

A Video Store UML

Class Diagram

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End of

“The Big Picture”

QUITTING TIME

lecture 1

Documents

software projects costs

downsoftware development

development consistency

development processproblems

software project costs

successful projects

budgetchallenged projects

development processa