Les 02
This document was uploaded by user and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this DMCA report form. Report DMCA
Overview
Download & View Les 02 as PDF for free.
More details
- Words: 1,388
- Pages: 6
Lesson 2
System Development Methodology
LESSON 2 SYSTEM DEVELOPMENT METHODOLOGY 1. DEFINITION Literally, the word "methodology" means a study of methods. But in the context of systems development, the word does not means 'a study of methods', but a method i.e. a defined way of doing things. In systems development context, a method can mean two different things: 1. A set of processes required to successfully build/develop a system, or 2. A technique or set of techniques used in systems development. The first meaning refers to the processes needed to develop systems. The collection of these processes is commonly called the systems development life cycle. The life cycle indicates all possible activities needed to complete a systems project. The processes specify what is to be done. They indicate there is a need to do something and produce some result. The second meaning of methodology refers to the way or how a process is to be carried out. These are the specific technique that must be used. These techniques are sometimes called the tools of systems development. Different techniques may be used given different conditions. 2. THE SYSTEM DEVELOPMENT LIFE CYCLE (SDLC) One approach of SDLC is the Structured Systems Analysis and Design (SSAD) developed by Ed Yourdon and his colleagues, which uses five stages of system development.
1. 2. 3. 4. 5.
Preliminary Investigation Systems analysis Systems design Systems Development Systems Implementation and Evaluation
3. SOME BASIC PRINCIPLES OF SYSTEMS DEVELOPMENT
Page 4
Lesson 2
• • • • •
System Development Methodology
The system is for the end-user. Get the end-user actively involved throughout systems development. Establish phases and tasks to better manage systems development project. Systems development tasks are not strictly sequential, they can overlap. Systems are capital investments. They should be economically justified as such. Establish checkpoints to reevaluate feasibility, and do not be afraid to cancel non-feasible projects despite sunk costs.
SYSTEMS REQUEST A written request from management or an end user triggers the start of the systems development life cycle. This written request is called a systems request. On the systems request, the end user or manager identifies the information system and the nature of the work that must be done for the information system. The work to be done usually is expressed as a problem statement that is a definition of the deficiencies in the information system or of the improvements desired. The work requested can be substantial; for example, the request could be for the creation of an information system to meet a newly identified business requirement, or it could be for the replacement of an existing information system that can no longer handle changing business requirements. In contrast, the work requested can be minor; the addition of a new report or changes to existing calculations are examples of minor systems requests. Substantial systems requests require many months or years of effort, while some minor systems requests require as little as a few hours of effort. PRELIMINARY INVESTIGATION The purpose of the preliminary investigation phase is to identify clearly the nature and scope of the problems mentioned in the systems request. Since identifying the problem is the focus of the preliminary investigation, this phase is sometimes called the problem definition phase. During the preliminary investigation phase you would not conduct a complete examination of the information system and its problems. Rather, your objective would be to spend a limited amount of time to produce the preliminary investigation report. This document is a report to management specifying the identified problems within the system and what further action you recommend. As shown in diagram, you would recommend one of three actions : •
If no problem exists and no further action is needed, then you will not conduct phases two through five of the systems development life cycle.
•
If the problem and its solution are minor, then your recommended action would be to proceed directly to phase four, systems development.
•
The majority of systems requests, however, require further detailed investigation. In these cases, your recommended action would be to begin the next phase, systems analysis.
SYSTEMS ANALYSIS The purpose of the systems analysis phase is to learn exactly what takes place in the current Page 5
Lesson 2
System Development Methodology
system, to determine and fully document in detail what should take place, and to make recommendations to management on the alternative solutions and their costs. Through the process of fact-finding or requirements determination, you first define all the functions performed by the current information system. At the same time, you determine what modifications are needed by the organization in the improved version of the information system. After you have obtained the facts, you then analyze and evaluate them in a systematic fashion in order to develop alternative plans to solve the problems found in the current information system. This process is called requirements analysis The end product you create for this life cycle phase is the system requirements document, which documents all end user and management requirements, all alternative plans and their costs, and your recommendations to management. After you present your results from this phase to management, management decides on the best alternative. There are three possible alternatives: •
If the selected choice involves the use of a software package, then your company must purchase the package, and you would continue on to either phase four, systems development (if package modifications are needed), or phase five, systems implementation and evaluation (if the package can be used as is).
•
If management's choice of alternatives is for in-house developed software, then you enter the third phase, systems design.
•
Finally, management might decide to terminate development. Management might choose to terminate development at any point of the SDLC due to high costs, changing priorities, or failure to meet objectives.
SYSTEMS DESIGN The purpose of the systems design phase is to determine how to construct the information system to best satisfy the documented requirements. You must design all required information system outputs, files, inputs, application software programs, and manual procedures. Also, you must design the internal and external controls, which are computer-based and manual steps that guarantee the information system will be reliable, accurate, and secure. The design is documented in the system design specification and presented to management and the end users for their review and approval. Management and end user involvement is critical so that there is no misunderstanding about what the information system is to do, how it will do it, and what it will cost. After all systems design steps have been completed and if the Page 6
Lesson 2
System Development Methodology
development is not terminated, you then enter the next phase, systems development.
SYSTEMS DEVELOPMENT Systems development is the phase during which the information system is actually constructed: applications programs are written, tested, and documented; operational documentation and procedures are completed; and end user and management review and approval is obtained. The end product of this phase is a completely functioning and documented information system. As is true with all other phases, the systems development phase ends after management has reviewed and approved all results of the phase.
SYSTEMS IMPLEMENTATION AND EVALUATION After the systems development phase is completed, you then proceed to systems implementation. Activities for this phase include conversion of data to the new system's files, final training of the end users, and the transition from the old system to the new system. It is at this point that the end users and management actually begin to use the constructed information system. As part of a complete systems development life cycle, provision is made to allow for post implementation systems evaluation at regular intervals. The purpose of these evaluations is to determine if the information system operates as proposed, and if the costs and benefits are as anticipated.
Page 7
Lesson 2
System Development Methodology
System Request
Phase 1 Preliminary Investigation
Preliminary Investigation report
Terminate Development
Phase 2 Systems Analysis
System Requirements Document
Terminate Development
Phase 3 Systems Design
System Design Specification
Terminate Development
Phase 4 Systems Development
Complete Functioning Info.System
Phase 5 – System Implementation & Evaluation
Operational Info.System
Replace Info.System
The Five Phases of the Systems Development Life Cycle & their Respective Outputs
Page 8
Lesson 2
System Development Methodology
The Three Phases of the Systems Development Life Cycle
Page 9
System Development Methodology
LESSON 2 SYSTEM DEVELOPMENT METHODOLOGY 1. DEFINITION Literally, the word "methodology" means a study of methods. But in the context of systems development, the word does not means 'a study of methods', but a method i.e. a defined way of doing things. In systems development context, a method can mean two different things: 1. A set of processes required to successfully build/develop a system, or 2. A technique or set of techniques used in systems development. The first meaning refers to the processes needed to develop systems. The collection of these processes is commonly called the systems development life cycle. The life cycle indicates all possible activities needed to complete a systems project. The processes specify what is to be done. They indicate there is a need to do something and produce some result. The second meaning of methodology refers to the way or how a process is to be carried out. These are the specific technique that must be used. These techniques are sometimes called the tools of systems development. Different techniques may be used given different conditions. 2. THE SYSTEM DEVELOPMENT LIFE CYCLE (SDLC) One approach of SDLC is the Structured Systems Analysis and Design (SSAD) developed by Ed Yourdon and his colleagues, which uses five stages of system development.
1. 2. 3. 4. 5.
Preliminary Investigation Systems analysis Systems design Systems Development Systems Implementation and Evaluation
3. SOME BASIC PRINCIPLES OF SYSTEMS DEVELOPMENT
Page 4
Lesson 2
• • • • •
System Development Methodology
The system is for the end-user. Get the end-user actively involved throughout systems development. Establish phases and tasks to better manage systems development project. Systems development tasks are not strictly sequential, they can overlap. Systems are capital investments. They should be economically justified as such. Establish checkpoints to reevaluate feasibility, and do not be afraid to cancel non-feasible projects despite sunk costs.
SYSTEMS REQUEST A written request from management or an end user triggers the start of the systems development life cycle. This written request is called a systems request. On the systems request, the end user or manager identifies the information system and the nature of the work that must be done for the information system. The work to be done usually is expressed as a problem statement that is a definition of the deficiencies in the information system or of the improvements desired. The work requested can be substantial; for example, the request could be for the creation of an information system to meet a newly identified business requirement, or it could be for the replacement of an existing information system that can no longer handle changing business requirements. In contrast, the work requested can be minor; the addition of a new report or changes to existing calculations are examples of minor systems requests. Substantial systems requests require many months or years of effort, while some minor systems requests require as little as a few hours of effort. PRELIMINARY INVESTIGATION The purpose of the preliminary investigation phase is to identify clearly the nature and scope of the problems mentioned in the systems request. Since identifying the problem is the focus of the preliminary investigation, this phase is sometimes called the problem definition phase. During the preliminary investigation phase you would not conduct a complete examination of the information system and its problems. Rather, your objective would be to spend a limited amount of time to produce the preliminary investigation report. This document is a report to management specifying the identified problems within the system and what further action you recommend. As shown in diagram, you would recommend one of three actions : •
If no problem exists and no further action is needed, then you will not conduct phases two through five of the systems development life cycle.
•
If the problem and its solution are minor, then your recommended action would be to proceed directly to phase four, systems development.
•
The majority of systems requests, however, require further detailed investigation. In these cases, your recommended action would be to begin the next phase, systems analysis.
SYSTEMS ANALYSIS The purpose of the systems analysis phase is to learn exactly what takes place in the current Page 5
Lesson 2
System Development Methodology
system, to determine and fully document in detail what should take place, and to make recommendations to management on the alternative solutions and their costs. Through the process of fact-finding or requirements determination, you first define all the functions performed by the current information system. At the same time, you determine what modifications are needed by the organization in the improved version of the information system. After you have obtained the facts, you then analyze and evaluate them in a systematic fashion in order to develop alternative plans to solve the problems found in the current information system. This process is called requirements analysis The end product you create for this life cycle phase is the system requirements document, which documents all end user and management requirements, all alternative plans and their costs, and your recommendations to management. After you present your results from this phase to management, management decides on the best alternative. There are three possible alternatives: •
If the selected choice involves the use of a software package, then your company must purchase the package, and you would continue on to either phase four, systems development (if package modifications are needed), or phase five, systems implementation and evaluation (if the package can be used as is).
•
If management's choice of alternatives is for in-house developed software, then you enter the third phase, systems design.
•
Finally, management might decide to terminate development. Management might choose to terminate development at any point of the SDLC due to high costs, changing priorities, or failure to meet objectives.
SYSTEMS DESIGN The purpose of the systems design phase is to determine how to construct the information system to best satisfy the documented requirements. You must design all required information system outputs, files, inputs, application software programs, and manual procedures. Also, you must design the internal and external controls, which are computer-based and manual steps that guarantee the information system will be reliable, accurate, and secure. The design is documented in the system design specification and presented to management and the end users for their review and approval. Management and end user involvement is critical so that there is no misunderstanding about what the information system is to do, how it will do it, and what it will cost. After all systems design steps have been completed and if the Page 6
Lesson 2
System Development Methodology
development is not terminated, you then enter the next phase, systems development.
SYSTEMS DEVELOPMENT Systems development is the phase during which the information system is actually constructed: applications programs are written, tested, and documented; operational documentation and procedures are completed; and end user and management review and approval is obtained. The end product of this phase is a completely functioning and documented information system. As is true with all other phases, the systems development phase ends after management has reviewed and approved all results of the phase.
SYSTEMS IMPLEMENTATION AND EVALUATION After the systems development phase is completed, you then proceed to systems implementation. Activities for this phase include conversion of data to the new system's files, final training of the end users, and the transition from the old system to the new system. It is at this point that the end users and management actually begin to use the constructed information system. As part of a complete systems development life cycle, provision is made to allow for post implementation systems evaluation at regular intervals. The purpose of these evaluations is to determine if the information system operates as proposed, and if the costs and benefits are as anticipated.
Page 7
Lesson 2
System Development Methodology
System Request
Phase 1 Preliminary Investigation
Preliminary Investigation report
Terminate Development
Phase 2 Systems Analysis
System Requirements Document
Terminate Development
Phase 3 Systems Design
System Design Specification
Terminate Development
Phase 4 Systems Development
Complete Functioning Info.System
Phase 5 – System Implementation & Evaluation
Operational Info.System
Replace Info.System
The Five Phases of the Systems Development Life Cycle & their Respective Outputs
Page 8
Lesson 2
System Development Methodology
The Three Phases of the Systems Development Life Cycle
Page 9
