SDLC

SDLC is the process of developing information systems through investigation, analysis, design, implementation and maintenance. SDLC is also known as information systems development or application development. It is also known as Waterfall Model

The software development life cycle (SDLC) is the entire process of formal, logical steps taken to develop a software product. The phases of SDLC can vary somewhat but generally include the following:

Requirements Analysis

Extracting the requirements of a desired software product is the first task in creating it. While customers probably believe they know what the software is to do, it may require skill and experience in software engineering to recognize incomplete, ambiguous or contradictory requirements.

Specification

Specification is the task of precisely describing the software to be written, in a mathematically rigorous way. In practice, most successful specifications are written to understand and fine-tune applications that were already well-developed, although safety-critical software systems are often carefully specified prior to application development. Specifications are most important for external interfaces that must remain stable.

Software architecture

The architecture of a software system refers to an abstract representation of that system. Architecture is concerned with making sure the software system will meet the requirements of the product, as well as ensuring that future requirements can be addressed. The architecture step also addresses interfaces between the software system and other software products, as well as the underlying hardware or the host operating system.

Coding

Reducing a design to code may be the most obvious part of the software engineering job, but it is not necessarily the largest portion.

Testing

Testing of parts of software, especially where code by two different engineers must work together, falls to the software engineer.

Documentation

An important task is documenting the internal design of software for the purpose of future maintenance and enhancement. Documentation is most important for external interfaces.

Software Training and Support

A large percentage of software projects fail because the developers fail to realize that it doesn't matter how much time and planning a development team puts into creating software if nobody in an organization ends up using it. People are occasionally resistant to change and avoid venturing into an unfamiliar area, so as a part of the deployment phase, its very important to have training classes for the most enthusiastic software users (build excitement and confidence), shifting the training towards the neutral users intermixed with the avid supporters, and finally incorporate the rest of the organization into adopting the new software. Users will have lots of questions and software problems which leads to the next phase of Software.

Maintenance

Maintaining and enhancing software to cope with newly discovered problems or new requirements can take far more time than the initial development of the software. Not only may it be necessary to add code that does not fit the original design but just determining how software works at some point after it is completed may require significant effort by a software engineer. About 2/3 of all software engineering work is maintenance, but this statistic can be misleading. A small part of that is fixing bugs.

Process Models

There are several methodologies or models that can be used to guide the software development lifecycle. Some of these include:
--Linear or Waterfall Model
--Rapid Application Development (RAD)
--Joint Application Development (JAD)
--Prototyping Model
--Fountain Model
--Spiral Model--Build
--Synchronize-and-Stabilize

Rapid Application Development

“Rapid Application Development (RAD) is an incremental software development process model that emphasises a very short development cycle typically 60-90 days”.The RAD approach encompasses the following phases:

1.Business Modelling
2.Data Modelling
3.Process Modelling
4.Application Generation
5.Testing and Turnover

Business Modelling

The information flow among business functions is modeled in am way that answers the following questions:1.What information drives the business process?2.What information is generated?3.Who generates it?4.Where does the information go?5.Who processes it?

Data Modelling

The information flow defined as part of the business modelling phase is refined into a set of data objects that are needed to support the business.The characteristic of each object is identified and the relationship between these objects are defined.

Process Modelling

The data objects defined in the data-modelling phase are transformed to achieve the information flow necessary to implement a business function. Processing the descriptions are created for adding,modifying,deleting or retrieving data object.

Application Generation

RAD assumes the use of the RAD tools like VB,VC++,Delphi etc rather than creatingsoftware using conventional third generation programming languages. The RAD works to reuse existing program components or create reusable components. In all cases,automated tools are used to facilitate construction of the software.

Testing and Turnover

Since the RAD process emphasizes reuse,many of the program components have already been tested. This minimize the testing and development time.