Thursday, May 17, 2007

Software Development Life-cycle


Definition: A systematic and orderly approach to solving problems related to software systems.

General problem-solving steps:

 • Planning - identify the scope and boundary of the problem, and plan the development strategy and goals.

    As software is always of a large system (or business), work begins by establishing the requirements for all system elements and then allocating some subset of these requirements to software. This system view is essential when the software must interface with other elements such as hardware, people and other resources. System is the basic and very critical requirement for the existence of software in any entity. So if the system is not in place, the system should be engineered and put in place. In some cases, to extract the maximum output, the system should be re-engineered and spruced up. Once the ideal system is engineered or tuned, the development team studies the software requirement for the system.

• Analysis - study and analyze the problems, causes, and effects. Then, identify and analyze the requirements that must be fulfilled by any successful solution.

This process is also known as feasibility study. In this phase, the development team visits the customer and studies their system. They investigate the need for possible software automation in the given system. By the end of the feasibility study, the team furnishes a document that holds the different specific recommendations for the candidate system. It also includes the personnel assignments, costs, project schedule, target dates etc.... The requirement gathering process is intensified and focussed specially on software. To understand the nature of the program(s) to be built, the system engineer or "Analyst" must understand the information domain for the software, as well as required function, behavior, performance and interfacing. The essential purpose of this phase is to find the need and to define the problem that needs to be solved .

• Design - if necessary, design the solution - not all solutions require design.

In this phase, the software development process, the software's overall structure and its nuances are defined. In terms of the client/server technology, the number of tiers needed for the package architecture, the database design, the data structure design etc... are all defined in this phase. A software development model is thus created. Analysis and Design are very crucial in the whole development cycle. Any glitch in the design phase could be very expensive to solve in the later stage of the software development. Much care is taken during this phase. The logical system of the product is developed in this phase.

• Implementation - implement the solution.

The design must be translated into a machine-readable form. The code generation step performs this task. If the design is performed in a detailed manner, code generation can be accomplished without much complication. Programming tools like compilers, interpreters, debuggers etc... are used to generate the code. Different high level programming languages like C, C++, Pascal, Java are used for coding. With respect to the type of application, the right programming language is chosen.

• Testingverify the solution works.

Once the code is generated, the software program testing begins. Different testing methodologies are available to unravel the bugs that were committed during the previous phases. Different testing tools and methodologies are already available. Some companies build their own testing tools that are tailor made for their own development operations.

• Support - analyze the implemented solution, refine the design, and implement improvements to the solution. Different support situations can thread back into the previous steps.

The software will definitely undergo change once it is delivered to the customer. There can be many reasons for this change to occur. Change could happen because of some unexpected input values into the system. In addition, the changes in the system could directly affect the software operations. The software should be developed to accommodate changes that could happen during the post implementation period.


DefinitionAn organized, documented set of procedures and guidelines for one or more phases of the software life cycle.

The physical implementation of the logical life cycle that incorporates

  1. step-by-step activities for each phase
  2. individual and group roles to be played in each activity
  3. deliverables and quality standards for each activity
  4. tools and techniques to be used for each activity.

A methodology is “how” the software development life-cycle is executed. There are many ways in which this can be achieved.

The Waterfall Model

The Spiral Model