is437: fall 2004 instructor: dr. boris jukic

IS437: Fall 2004

Instructor: Dr. Boris Jukic

Introduction

Main Objectives of This Course Exposure to a Visual Programming Language, its main

components, features and development practices. (textbook, labs, assignments)

Exposure to an Object Oriented Programming Language and Main OO concepts. (textbook, labs, assignments)

Development of Standard Business Application in a Multi-Tier (Client Sever) Architecture. Database Layer Connectivity with User Interface and Business

Logic Layer (additional material, labs, assignments)

Understanding Business Application Development and Design Practices in a practical context. (additional material, labs, assignments)

Business Application Development and Design

Two Main Approaches Traditional Approach: Based on Abstract

Design and Documentation (Waterfall Model)

RAD Approach: Based on Series of Prototyping Sessions (RAD: Rapid Application Development)

Those approaches are not mutually exclusive

Traditional Information System Development

Six traditional phases

Traditional Information System Development Standard Sequential Waterfall Method

for Application Development 1. Requirements Gathering and Elicitation (what does a client need?)

|2. Analysis Phase (Specification Document, what is system supposed to

do, what are its tasks)|

3. Design (specifying, through models, algorithms, data structures and other representations how is system/application supposed to

accomplish the required tasks)|

4. Implementation (Translating the design into the actual application coded in the language of choice)

Iteration vs. Incrementation

(a) Iteration versus (b) incrementation

Iteration and Incrementation (contd)

Iteration and incrementation are used in conjunction with one another

There is no single “requirements phase” or “design phase”

Instead, there are multiple instances of each phase

Iteration and Incrementation in Traditional Approach

Iterative and Incremental Life-Cycle Model in Traditional Approach

Sample life cycle of an information system

Traditional Approach: Phases and Workflows

Sequential phases do not exist in the real world

Instead, the five core workflows (activities) are performed over the entire life cycle Requirements workflow Analysis workflow Design workflow Implementation workflow Test workflow

Workflows All five core workflows are performed over the

entire life cycle However, at most times one workflow

predominates Examples:

At the beginning of the life cycle The requirements workflow predominates

At the end of the life cycle The implementation and test workflows predominate

Planning and documentation activities are performed throughout the life cycle

Iteration and Incremenation in Phases and Workflows

Iteration is performed during each incrementation

Non-Traditional Approach : Rapid Application Development (RAD)

Characteristics of RAD processes The processes of specification, design and

implementation are concurrent. There is no detailed specification and design documentation is minimised.

The system is developed in a series of increments. End users evaluate each increment and make proposals for later increments.

System user interfaces are usually developed using an interactive development system.

Agile methods Dissatisfaction with the overheads involved in

traditional design methods led to the creation of agile methods. These methods: Focus on the code rather than the design; Are based on an iterative approach to software

development; Are intended to deliver working software quickly and

evolve this quickly to meet changing requirements. Agile methods are probably best suited to

small/medium-sized business systems or PC products.

Extreme programming Perhaps the best-known and most widely

used agile method. Extreme Programming (XP) takes an

‘extreme’ approach to iterative development. New versions may be built several times per day; Increments are delivered to customers every 2

weeks; All tests must be run for every build and the build

is only accepted if tests run successfully.

The XP release cycle

Break downstories to tasks

Select userstories for this

releasePlan release

Releasesoftware

Evaluatesystem

Develop/integrate/test software

XP and agile principles Incremental development is supported through

small, frequent system releases. Customer involvement means full-time customer

engagement with the team. Pair programming fosters collective ownership and

a process that avoids long working hours. Change supported through regular system releases. Maintaining simplicity through constant refactoring of

code.

Requirements scenarios

In XP, user requirements are expressed as scenarios or user stories.

These are written on cards and the development team break them down into implementation tasks. These tasks are the basis of schedule and cost estimates.

The customer chooses the stories for inclusion in the next release based on their priorities and the schedule estimates.

Example: Story card for document downloading

Downloading and printing an article

First, you select the article that you want from a displayed list. Youthen have to tell the system how you will pay for it - this can eitherbe through a subscription, through a company account or by creditcard.

After this, you get a copyright form from the system to fill in and,when you have submitted this, the article you want is downloadedonto your computer.

You then choose a printer and a copy of the article is printed. Youtell the system if printing has been successful.

If the article is a print-only article, you canÕt keep the PDF versionso it is automatically deleted from your computer.

Task cards for document downloading

Task 1: Implement principal workflow

Task 2: Implement article catalog and selection

Task 3: Implement payment collection

Payment may be made in 3 different ways. The userselects which way they wish to pay. If the userhas a library subscription, then they can input thesubscriber key which should be checked by thesystem. Alternatively, they can input an organisationalaccount number. If this is valid, a debit of the costof the article is posted to this account. Finally, theymay input a 16 digit credit card number and expirydate. This should be checked for validity and, ifvalid a debit is posted to that credit card account.

Pair programming

In XP, programmers work in pairs, sitting together to develop code.

This helps develop common ownership of code and spreads knowledge across the team.

It serves as an informal review process as each line of code is looked at by more than 1 person.

It encourages refactoring as the whole team can benefit from this.

Measurements suggest that development productivity with pair programming is similar to that of two people working independently.

Visual programming Scripting languages such as Visual Basic

support visual programming where the prototype is developed by creating a user interface from standard items and associating components with these items

A large library of components exists to support this type of development

These may be tailored to suit the specific application requirements

Visual programming with reuse

File Edit Views Layout Options Help

GeneralIndex

Menu componentDate component

Range checkingscript

Tree displaycomponent

Draw canvascomponent

User promptcomponent +

script

12th January 2000

3.876

Prototyping

Prototype (in Business Application Development) is an experimental system is developed as a basis for formulating the requirements may be used. This system is thrown away when the system specification has been agreed.

Software prototyping A prototype is an initial version of a system

used to demonstrate concepts and try out design options.

A prototype can be used in: The requirements engineering process to help

with requirements elicitation and validation; In design processes to explore options and

develop a UI design;

Benefits of prototyping

Improved system usability. A closer match to users’ real needs. Improved design quality. Improved maintainability. Reduced development effort.

Throw-away prototypes

Prototypes should be discarded after development as they are not a good basis for a production system: It may be impossible to tune the system to

meet non-functional requirements; Prototypes are normally undocumented; The prototype structure is usually degraded

through rapid change; The prototype probably will not meet normal

organisational quality standards.

Key points An iterative approach to software development

leads to faster delivery of software. Agile methods are iterative development

methods that aim to reduce development overhead and so produce software faster.

Extreme programming includes practices such as systematic testing, continuous improvement and customer involvement.

A throw-away prototype is used to explore requirements and design options.

History of BASIC

• Beginner’s All-purpose Symbolic Instruction Code• Dartmouth College, 1964• primarily intended as instructional tool before more complex languages (FORTRAN) can be tackled by students • easy to use, needed only 4K memory to run:

05 a = 5010 b = 10015 c = a + b20 print c25 end

• popular language in business schools • in late 1980s, visual components were added

Evolution of Programming

Machine Code, Assembly Languages High Level Languages: Structured (flowcharts,

pseudo code) and Procedural FORTRAN, Pascal, Cobol

Object Based and Object Oriented Programming (OOP) C++, Java, VB.Net Building block approach: software reuse Definition of programming skill is fundamentally changed

Structure of Visual Basic

VISUAL

BASICProgram code

Graphical User Interface

History of Visual BASIC

VB 1: May 1991 VB 2: November 1992 VB 3: June 1993 VB 4: October 1996 VB 5: April 1997 VB 6: October 1998 VB. Net: 2002

The .Net Framework

The goal is to access information anywhere and anytime with any device using the common infrastructure of the Internet.

http://www.microsoft.com/net/basics/framework.asp

MS .Net Architecture

Source code: Visual Basic, C++, COBOL, etc.

Microsoft Intermediate Language (MSIL)

Platform-specific code

compiler

Development tool

VB .Net vs. VB 6

Enhanced development environment for desk top applications

Enhanced development environment for Web-based applications (ASP.Net, XML)

Enhanced database management (ADO.Net) Fully object-oriented

The Object Model in VB: examples

Objects: forms , controls, textboxes Properties: text, name, size, location Methods: Form.close, messagebox.show Events: clicking of a button, closing a

window, changing the state of a radio button Class (button) vs. Instance of a class (OK

button)

Characteristics of VB

proprietary dynamic (ever improving) complex (features laden) powerful (productivity enhancing) the most popular programming

language (3.2 million programmers)

Popular Business Oriented programming languages

COBOL Visual Basic

Mainframes Desktop

Transaction processing

Individual users

Web-based applications