 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | |
| By N2H | ||||||||||||||||||||||
System development Lifecycle (SDLC)
October 25, 2007
If you're new here, you may want to subscribe to my RSS feed. Thanks for visiting and have a nice day!
The System Development Life Cycles!
The waterfall model also knows as the SDLC was originally published in 1970 by W. Royce. This is a step by step way of developing projects.
The waterfall model is broken down into stages and each stage is completed before proceeding to the next.
Stages of the waterfall model
In the waterfall model there are seven stages of the development of a project.
-
Problem Definition
In this stage the users or the manager realizes that the Information system is no longer reflective of the existing business which may have expanded or that they need to computerize their manual operations.
This problem could come about due to complaints by users or by formal review of the Information system.
An Analyst examines whether there is a problem and then studies the problem in depth, and an authorization to conduct a feasibility study is given. This authorization is the output or the deliverable at this stage. Thus users, managers and Analyst are used in this stage.
-
Feasibility Study:
In this stage the Analyst examines whether a new system is feasible. He assesses the magnitude of this problem and decides the scope of the project. He examines the problem of the current system and what will be required of the new system.
Economical, technical and operational feasibilities are done. The output is a feasibility study report.
Tools used in this stage are fact gathering Techniques and Estimation Techniques. Users and the Analyst plus management are heavily involved.
-
Analysis
In this stage detailed investigation are done about the current system. This include
-
reading existing documentation
-
Interviewing the users
-
Observing work being done
-
Observing current procedures
-
Questionnaires
After gathering the needed facts about the existing system the Analyst diagrams the current system and then considers the functions of the new system. A new set of diagrams which incorporate new functions is made. A prototype is also generated using these gathered facts to help uncertain users know what they want in the new system. Thus it helps to reveal new requirements. The Analysts makes a problem specification using fact gathering tools, prototypes, DFD, Data models process specifically etc. Users are involved so is the Analysts
-
Design:
In this stage basically the hardware and software are ordered so that they can arrive in time for construction.
Functional diagrams are translated into hierarchial diagrams by the analyst so as to identify what programs are needed and how they relate to one another. The analyst decides on the program structure, program interface and the hierarchy in which programs will be arranged.
The Analyst ensures quality designs, incorporates security measures, designs easy to use input forms, output reports interfaces.
The Database designer fulfills the file requirements. The output is a design specification.
Tools used are DFD, Data Dictionary, Data models, prototypes, system flowcharts: The personnel involved are users, Analysts, Database Designer.
-
Construction
The computer environment is prepared, the programs to be written are done and they are tested, user documentation and training manuals are developed.
Computer environment being prepared means electrical wires, network cables are installed, furniture, air conditioning are in place. The computers are installed and tested.
Programs are written per the program and design specifications. The programs are tested using walk through and group reviews. The Analyst supervises the writing of training manuals and user documentations. User documentation includes user manuals, user quick reference guides, on-screen help etc.
People involved are programmers and analysts. Tools used are structured, walkthroughs, CASE tools etc
6. Conversion
The Analyst helps the staff to convert from the old system to the new one. The Analysts oversees the transfer of data files electronically to the new system.
Conversion can be done in various ways
-
-
Phase Conversion
-
Parallel Conversion
-
Direct Conversion
- Pilot Conversion
-
Output is that the system is operational and the tools used are automated data transfer programs.
7. Maintenance:
System modifications are made to the system after the system is operational. Maintenance can be
(1) Perfective (3) preventive
(2) Corrective (4) adaptive
The traditional SDLC has a number of good features. It has been well tried and tested. However this method has been known to have several drawbacks.
Some of the drawbacks of SDLC are user dissatisfaction. SDLC assumes that the user already knows all their requirements thus they expect the users to tell them their requirements and once documented the requirements should remain unchanged, thus they develop the system with these requirements only to find that when the system is implemented, it does not provide for their need or their changed requirements, hence they become dissatisfied with the system.
Failure to meet the needs of the management in that the system developed with the approach are mainly operational processing systems such as payroll, invoicing which deals with low level operational tasks, thus ignoring the information needs of the tactical and top management, that they require to make decisions e.g. which products to stop selling e.t.c.
Unambitious system design, in that the systems developed by this approach often tend to computerize the manual operational tasks like invoicing, thus they tend to come up with systems design that are similar to the existing manual process.
Application backlog, this approach has many phases with sub phases, It may take many weeks to complete a phase, thus the overall development time of a single project may be months and if there are other system waiting to be developed using this process, it may cause a backlog.
Maintenance workload since the firm may have many systems to develop, the development is often quick and ‘dirty’ so as to make the delivery date, thus brings about systems which take a huge effort to maintain.
Problems with documentation, this approach provides for documentation of the implementation process which is very ideal, but the notation of the documentation is towards the computer person in that the documentation is highly technical and not easy to understand by the user.
Comments
Got something to say?
You must be logged in to post a comment.
Powered by FireStats