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The systems development life cycle (SDLC), or software development process, or Software Development Life Cycle in systems engineering, information systems and software engineering, is a process of creating or altering information systems, and the models and methodologies that people use to develop these systems. In software engineering, the SDLC concept underpins many kinds of software development methodologies. These methodologies form the framework for planning and controlling the creation of an information system: the software development process.
The systems life cycle (SLC) is a methodology used to describe the process for building information systems, intended to develop information systems in a very deliberate, structured and methodical way, reiterating each stage of the life cycle. The systems development life cycle, according to Elliott & Strachan & Radford (2004), "originated in the 1960s, to develop large scale functional business systems in an age of large scale business conglomerates. Information systems activities revolved around heavy data processing and number crunching routines".
Several systems development frameworks have been partly based on SDLC, such as the structured systems analysis and design method (SSADM) produced for the UK government Office of Government Commerce in the 1980s. Ever since, according to Elliott (2004), "the traditional life cycle approaches to systems development have been increasingly replaced with alternative approaches and frameworks, which attempted to overcome some of the inherent deficiencies of the traditional SDLC".
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The System Development Life Cycle framework provides a sequence of activities for system designers and developers to follow. It consists of a set of steps or phases in which each phase of the SDLC uses the results of the previous one.
A Systems Development Life Cycle (SDLC) adheres to important phases that are essential for developers, such as planning, analysis, design, and implementation, and are explained in the section below.It include evaluation of present system, information gathering, feasibility study and request approval. A number of system development life cycle (SDLC) models have been created: waterfall, fountain, spiral, build and fix, rapid prototyping, incremental, and synchronize and stabilize. The oldest of these, and the best known, is the waterfall model: a sequence of stages in which the output of each stage becomes the input for the next. These stages can be characterized and divided up in different ways, including the following:
In the following example (see picture) these stage of the systems development life cycle are divided in ten steps from definition to creation and modification of IT work products:
Not every project will require that the phases be sequentially executed. However, the phases are interdependent. Depending upon the size and complexity of the project, phases may be combined or may overlap.
The system investigation stage addresses the needs or opportunities that can be achieved by a sponsor or IT proposal. During this step, we must consider all current priorities that would be affected and how they should be handled. Before any system planning is done, a feasibility study should be conducted to determine if creating a new or improved system is a viable solution. This will help to determine the costs, benefits, resource requirements, and specific user needs required for completion. The development process can only continue once management approves of the recommendations from the feasibility study.
Following are different components of the feasibility study:
The goal of system analysis is to determine where the problem is in an attempt to fix the system.This step involves breaking down the system in different pieces to analyze the situation, analyzing project goals, breaking down what needs to be created and attempting to engage users so that definite requirements can be defined.
In systems design the design functions and operations are described in detail, including screen layouts, business rules, process diagrams and other documentation. The output of this stage will describe the new system as a collection of modules or subsystems.
The design stage takes as its initial input the requirements identified in the approved requirements document. For each requirement, a set of one or more design elements will be produced as a result of interviews, workshops, and/or prototype efforts.
Design elements describe the desired software features in detail, and generally include functional hierarchy diagrams, screen layout diagrams, tables of business rules, business process diagrams, pseudo-code, and a complete entity-relationship diagram with a full data dictionary. These design elements are intended to describe the software in sufficient detail that skilled programmers may develop the software with minimal additional input design.
The code is tested at various levels in software testing. Unit, system and user acceptance testings are often performed. This is a grey area as many different opinions exist as to what the stages of testing are and how much, if any iteration occurs. Iteration is not generally part of the waterfall model, but usually some occur at this stage. In the testing the whole system is test one by one
Following are the types of testing:
The deployment of the system includes changes and enhancements before the decommissioning or sunset of the system. Maintaining the system is an important aspect of SDLC. As key personnel change positions in the organization, new changes will be implemented. There are two approaches to System Development, there are traditional approach (structured) and Object Oriented. Information Engineering includes traditional system approach or it also called as Structured Analysis and Design Technique. Object Oriented approach views information system as the collection of objects that integrated each other's to make a full complete information system.
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The final phase of the SDLC is to measure the effectiveness of the application and evaluate potential enhancements....
The Systems Analysis and Design (SAD) is the process of developing Information Systems (IS) that effectively use hardware, software, data, processes, and people to support the company's businesses objectives. System Analysis and Design can be considered the meta-development activity, which serves to set the stage and bound the problem. SAD can be leveraged to set the correct balance among competing high-level requirements in the functional and non-functional analysis domains. System Analysis and Design interacts strongly with distributed Enterprise Architecture, Enterprise I.T. Architecture, and Business Architecture, and relies heavily on concepts such as partitioning, interfaces, personae and roles, and deployment/operational modeling to arrive at a high-level system description. This high level description is then further broken down into the components and modules which can be analyzed, designed, and constructed separately and integrated to accomplish the business goal. SDLC and SAD are cornerstones of full-lifecycle product and system planning.
Object-oriented analysis (OOA) is the process of analyzing a task (also known as a problem domain), to develop a conceptual model that can then be used to complete the task. A typical OOA model would describe computer software that could be used to satisfy a set of customer-defined requirements. During the analysis phase of problem-solving, a programmer might consider a written requirements statement, a formal vision document, or interviews with stakeholders or other interested parties. The task to be addressed might be divided into several subtasks (or domains), each representing a different business, technological, or other areas of interest. Each subtask would be analyzed separately. Implementation constraints, (e.g., concurrency, distribution, persistence, or how the system is to be built) are not considered during the analysis phase; rather, they are addressed during object-oriented design (OOD).
The conceptual model that results from OOA will typically consist of a set of use cases, one or more UML class diagrams, and a number of interaction diagrams. It may also include some kind of user interface mock-up.
The input for object-oriented design is provided by the output of object-oriented analysis. Realize that an output artifact does not need to be completely developed to serve as input of object-oriented design; analysis and design may occur in parallel, and in practice the results of one activity can feed the other in a short feedback cycle through an iterative process. Both analysis and design can be performed incrementally, and the artifacts can be continuously grown instead of completely developed in one shot.
Some typical input artifacts for object-oriented design are:
The SDLC phases serve as a programmatic guide to project activity and provide a flexible but consistent way to conduct projects to a depth matching the scope of the project. Each of the SDLC phase objectives are described in this section with key deliverables, a description of recommended tasks, and a summary of related control objectives for effective management. It is critical for the project manager to establish and monitor control objectives during each SDLC phase while executing projects. Control objectives help to provide a clear statement of the desired result or purpose and should be used throughout the entire SDLC process. Control objectives can be grouped into major categories (domains), and relate to the SDLC phases as shown in the figure.
To manage and control any SDLC initiative, each project will be required to establish some degree of a Work Breakdown Structure (WBS) to capture and schedule the work necessary to complete the project. The WBS and all programmatic material should be kept in the "project description" section of the project notebook. The WBS format is mostly left to the project manager to establish in a way that best describes the project work.
There are some key areas that must be defined in the WBS as part of the SDLC policy. The following diagram describes three key areas that will be addressed in the WBS in a manner established by the project manager.
The upper section of the work breakdown structure (WBS) should identify the major phases and milestones of the project in a summary fashion. In addition, the upper section should provide an overview of the full scope and timeline of the project and will be part of the initial project description effort leading to project approval. The middle section of the WBS is based on the seven systems development life cycle (SDLC) phases as a guide for WBS task development. The WBS elements should consist of milestones and "tasks" as opposed to "activities" and have a definitive period (usually two weeks or more). Each task must have a measurable output (e.x. document, decision, or analysis). A WBS task may rely on one or more activities (e.g. software engineering, systems engineering) and may require close coordination with other tasks, either internal or external to the project. Any part of the project needing support from contractors should have a statement of work (SOW) written to include the appropriate tasks from the SDLC phases. The development of a SOW does not occur during a specific phase of SDLC but is developed to include the work from the SDLC process that may be conducted by external resources such as contractors and struct.
Baselines are an important part of the systems development life cycle (SDLC). These baselines are established after four of the five phases of the SDLC and are critical to the iterative nature of the model . Each baseline is considered as a milestone in the SDLC.
Complementary software development methods to systems development life cycle (SDLC) are:
|SDLC||RAD||Open source||Objects||JAD||Prototyping||End User|
|Time frame||Long||Short||Medium||Any||Medium||Short||Short |
|Users||Many||Few||Few||Varies||Few||One or two||One|
|MIS staff||Many||Few||Hundreds||Split||Few||One or two||None|
|Documentation and training||Vital||Limited||Internal||In Objects||Limited||Weak||None|
|Integrity and security||Vital||Vital||Unknown||In Objects||Limited||Weak||Weak|
Few people in the modern computing world would use a strict waterfall model for their systems development life cycle (SDLC) as many modern methodologies have superseded this thinking. Some will argue that the SDLC no longer applies to models like Agile computing, but it is still a term widely in use in technology circles. The SDLC practice has advantages in traditional models of software development, that lends itself more to a structured environment. The disadvantages to using the SDLC methodology is when there is need for iterative development or (i.e. web development or e-commerce) where stakeholders need to review on a regular basis the software being designed. Instead of viewing SDLC from a strength or weakness perspective, it is far more important to take the best practices from the SDLC model and apply it to whatever may be most appropriate for the software being designed.
A comparison of the strengths and weaknesses of SDLC:
|Control.||Increased development time.|
|Monitor large projects.||Increased development cost.|
|Detailed steps.||Systems must be defined up front.|
|Evaluate costs and completion targets.||Rigidity.|
|Documentation.||Hard to estimate costs, project overruns.|
|Well defined user input.||User input is sometimes limited.|
|Ease of maintenance.|
|Development and design standards.|
|Tolerates changes in MIS staffing.|
An alternative to the SDLC is rapid application development, which combines prototyping, joint application development and implementation of CASE tools. The advantages of RAD are speed, reduced development cost, and active user involvement in the development process.
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