Overview of Software Engineering

• •The System Development Life Cycle (SDLC) is a process of understanding how an Information System can support business needs by designing a system, building it and  delivering it to users
• The System Analysis is not an easy task:

  -1996 survey shows that 42% of the corporate IS Projects were abandon before completion.

  -Many of the systems that are not abandoned are delivered late, cost far more than planned and have fewer features than originally planned.
• The key person in the SDLC is the system analyst, who analyzes the business situation, identifies opportunities for improvements and design information system.
• The main objective of the system analyst is not to create system but create a value for the organization.
• The SDLC has 7 fundamental phases each is itself composed of series of steps which relies upon techniques and produce deliverables.

  -Planning

  -Analysis

  -Design

  -Development

  -Testing

  -Deployment

  -Maintenance
• The two important points to understand about SDLC.

  -Get a general sense of the phases and steps through which the IT projects move and some of the techniques that produce certain deliverables.

  -SDLC is a process of “gradual refinement”.
• Planning Phase :

  Fundamental process of understanding why an information system should be build and determining how the project team will go about building it.

  It has two steps:

  -Project Initiation

  -Project Management
• Planning:

  -During Project Initiation

  ->The system’s business value is identified in the form of system’s request.

  ->Analyze feasibility

  -->Technical feasibility

  -->Economic feasibility

  -->Organizational Feasibility

  -->Schedule Feasibility
• Planning :

  -During Project Management

  ->Create a work plan

  ->Staff the project

  ->Control and direct the project through the entire SDLC

  -->The deliverable for project management is the Project Plan, which describes how the project team will go about developing the system.
• _____ Phase:

  -The analysis phase answers the questions of who will use the system, what the system will do, and where and when it will be used.

  -During this phase, the analyst:

  ->Investigate current systems

  ->Identifies opportunities for improvement

  ->Develops concept for new system
• Analysis Phase Three Steps

  -Analysis Strategy- is developed to guide the project team’s effort. Includes analysis of current system (as-is system) and the new system (to-be system)

  -Requirements Gathering –develop concepts, business model e.g data and process model.

  -System Proposal- presented to the project sponsor and other key decision makers who decide whether the project will move forward.
• _____ Phase

  -The design phase decides how the system will operate, in terms of hardware, software and network infrastructure; the user interface, forms and reports; and the specific programs, databases, and files that will be needed.

  -The design phase has 4 steps:

  ->Design strategy

  ->Architectural design

  ->Database and file specification

  ->Program design
• -Design Strategy:

  It clarifies whether the system will be developed by the company’s own programmer or outsourced, or buy an existing package.

  -Architectural Design :

  This describes the hardware, software and network infrastructure to be used. The interface design specifies how the users will move through the system and reports that the system will use.

  -Database and file specification:

  These defines what data will be stored and where the data will be stored .

  -Program Design :

  Defines the programs that need to be written and exactly what each program will do.
• Development:

  This is where the actual system is build. This is the phase that gets the most attention, because it is the longest and most expensive part of the development process.

  - It has three steps:

  ->System Construction

  -> Installation

  ->Support Plan
• -System Construction :

  The system is built and tested to ensure it performs as designed. Testing is one of the most critical steps in implementation

  -Installation:

  is the act of making the program ready for execution. Installation typically involves code being copied/generated from the installation files to new files on the local computer for easier access by the operating system.

  -Support Plan:

  This include a formal or informal post implementation review as well as systematic way for identifying major and minor changes needed for the system
• System Analysis and Design, Shelly et.al

  A) Direct Cutover

  B) Parallel Operation

  C) Pilot Operation

  D) Phased Operation

  
• The Installation Process:

  -Direct Cut Over Approach

  ->The new system replaces the old system.
• The Installation Process:

  -Parallel Operation:

  ->Both the old and new system is operated for a month or two until it is clear that there is no bug in the system.

  ->Data is input into both systems, and output generated by the new system is compared with the equivalent output from the old system.

  ->The obvious advantage is lower risk

  ->If the new system does not work correctly, you can use the old system as a backup

  ->Easier to verify that the new system is working properly under parallel operation than under direct cutover
• The Installation Process:

  -Pilot Operation :

  ->The pilot operation changeover method involves implementing the complete new system at a selected location of the company.

  ->The group that uses the new system first is called the pilot site

  ->The old system continues to operate for the entire organization

  -> After the system proves successful at the pilot site, it is implemented in the rest of the organization, usually using the direct cutover method . Restricting the implementation to a pilot site reduces the risk of system failure.
• The Installation Process :

  -Phased Operation:

  The new system was installed in one part of organization as an initial trial and gradually installed in others.
• Risk & Cose

  A) Direct Cutover

  B) Pilot Operation

  C) Phased Operation

  D) Parallel Operation

  
• Post-Implementation Tasks:

  Post-Implementation Evaluation

  --Includes feedback for the following areas:

  ->Accuracy, completeness, and timeliness of information system output

  ->User satisfaction

  ->System reliability and maintainability

  ->Adequacy of system controls and security measures

  ->Hardware efficiency and platform performance