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Introduction to Information Technology Turban, Rainer and Potter John Wiley & Sons, Inc.Copyright 2005

A Technical View of System Analysis and

Design

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Chapter Outline

Developing an IT architectureOverview the Traditional SDLCAlternative methods and tools for systems developmentComponent- based development and web services

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Learning Objectives

Describe the hierarchy and steps of IT architecture.Describe the SDLC and its advantages and limitations.Describe the major alternative methods and tools for building information systems.Describe the use of component- based development and web services.

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TG6.1 Developing an IT Architecture

Koontz (2000) suggested a six-step process for developing an IT architecture

Step1: Business goals and vision. The system analyst reviews the relevant business goals and vision.

Step 2 : Information architecture. A company analyst defines the information necessary to fulfil the objectives of step 1.

Step 3: Data architecture. What data you have and what you want to get form customers, including Web-generated data.

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Step 4: Application architecture. Define the components or modules of the applications that will interface with the required data. Build the conceptual framework of an application, but not the infrastructure that will support it.

Step 5: Technical architecture. Formally examine the specific hardware and software required to support the analysis in previous step.

Step 6: Organizational architecture. An organizational architecture deals with the human resources and procedure required by steps 1 through 5

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TG6.2 Overview of SDLC

Systems development life cycle (SDLC) is a structured framework used for large IT projects, that consists of sequential processes by which information systems are developed.

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An eight- stage system development life cycle (SDLC)

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Waterfall approach. SDLC approach in which tasks in one stage were completed before the work proceeded to next stage Systems analysts. IS professionals who specialize in analyzing and designing information systems.Programmers. IS professionals who modify existing computer programs or write new computer programs to satisfy user requirements.Technical specialist. Experts on a certain type of technology, such as databases or telecommunications

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Systems stakeholders

All people who are affected by changes in information systems

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Systems investigation begins with the business problem (or business opportunity).

The next task in the systems investigation stage is the feasibility study that gauges the probability of success of a proposed project and provides rough assessment of the project's feasibility.

Systems investigation

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Technical feasibility: Assessment of whether hardware, software and communications components can be developed and /or acquired to solve a business problem.

Economic feasibility: Assessment of whether a project is an acceptable financial risk and if the organization can afford the expense and time needed to complete it.

Feasibility study

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Return on investment. The ratio of the net income attributable to a project divided by the average assets invested in the project.Net present value. The net amount by which project benefits exceed project costs of capital and the time value of money.Breakeven analysis. Method that determines the point at which the cumulative cash flow from a project equals the investment made in the project.

Economic feasibility

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Organizational feasibility . organization’s ability to access the proposed project.Behavioural feasibility. Assessment of the human issues involved in a proposed project, including resistance to change and skills and training needs.

Feasibility study cont…

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Systems analysis

The examination of the business problem that the organization plans to solve with an information system. This stage defines the business problem, identifies its causes, specifies the solution and identifies the information requirements that the solution must satisfy

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Organization have three basic solutions to any business problem relating to an information system:

Do nothing and continue to use the existing system unchanged,

Modify or enhance the existing system,

Develop a new system.

Systems Analysis cont…

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There are problems associated with eliciting information requirement, regardless of the method used by the analyst.

The business problem may be poorly defined The users may not know exactly what the problem is, what they want or what they need.Users may disagree with each other about business procedures or even about the business problem. The problem may not be information related, but may require other solutions, such as a change in management or additional training.

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The system analysis stage produces the following information: Strengths and weaknesses of the existing system Functions that the new system must have to

solve the business problem. User information requirements for the new

system.

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System analysis describes what a system must do to solve the business problem and systems design describes how the system will accomplish this task . The deliverable of the systems design phase is the technical design that specifies the following :System outputs, inputs and user interfacesHardware, software, databases, telecommunications, personnel and proceduresHow these components are integrated

This output represents the set of system specification

Systems design

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System design encompasses two major aspects of the new system:

Logical system design: states what the system will do, using abstract specifications.

Physical system design: states how the system will perform its functions, with actual physical specification.

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The translation of a system’s design specification into computer code.

Programming

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Testing check to see if the computer code will produce the expected and desired results under certain conditions

Testing is designed to delete errors (bugs) in the computer code. These errors are of two types . Syntax errors ( e.g., misspelled word or a misplaced comma) and logic errors that permit the program to run but result in incorrect output

Testing

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Implementation or deployment is the process of converting from the old system to the new system. Organizations use four major conversion strategies ; parallel , direct , pilot and phased.

Parallel conversion. Implementation process in which the old system and the new system operate simultaneously for a period of time.

Direct conversion. Implementation process in which the old system is cut off and the new system turned on at a certain point in time.

Implementation

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Pilot conversion. Implementation process that introduces the new system in one part of the organization on a trial basis, when new system is working property, it is introduced in other parts of the organization.Phased conversion. Implementation process that introduces components of the new system in stages, until the entire new system is operational.

Implementation cont…

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Operation and maintenance

Systems need several types of maintenance.

Debugging: A process that continues throughout the life of the system.

Updating: updating the system to accommodate changes in business conditions.

Maintenance: that adds new functionally to the system –adding new features to the existing system without disturbing its operation.

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Prototyping

Joint application design (JAD)

Rapid application development (RAD)

Object- oriented development

Other methods

TG6.3 Alternative methods and tools for systems development

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Prototyping. Approach that defines an initial list of user requirements, builds a prototype system and then improves the system in several iterations based on users’ feedback.

Joint application design (JAD). A group –based tool for collecting user requirements and creating system designs.

Alternative methods cont…

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Rapid application development . A development method that uses special tools and an iterative approach to rapidly produce a high-quality system.

Computer-aided software engineering (CASE). Development approach that uses specialized tools to automate many of the tasks in the SDLC; upper CASE tools in SDLC automate the early stages of the SDLC, and lower case tools automate the later stages.

Alternative methods cont…

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Integrated Computer Assisted software Engineering (ICASE) Tools . CASE tools that provide links between upper CASE and lower CASE tools.

Object- oriented development. Begins with aspects of the real world that must be modelled to perform a task.

Alternative methods cont…

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CBD: A method that uses pre-programmed components to develop application.

Web service in system development: Self-contained, self-describing business and consumer modular applications, delivered over the Internet, that users can select and combine through almost any device.

TG6.4 Component-based development (CBD) and web service

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Web services advantages and limitations

Advantage Disadvantage

Greater interoperability and lower costs due to universal, open, text-based standards

Standards still being defined

Enable software running on different platforms to communicate with each other

Require programming skill to implement

Promote modular programming and reuse of existing software.

Security: applications may be able to bypass security barriers

Operate on existing Infrastructure, so are easy and inexpensive to implement.

Can be implemented incrementally

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