World Library  
Flag as Inappropriate
Email this Article

System development life cycle

Article Id: WHEBN0023807406
Reproduction Date:

Title: System development life cycle  
Author: World Heritage Encyclopedia
Language: English
Subject: Index of software engineering articles
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

System development life cycle

For other uses, see SDLC (disambiguation).


The Systems development life cycle (SDLC), sometimes referred to as the Application development life-cycle, is used in systems engineering, information systems and software engineering, and represents a process for creating or altering information systems, and the models and methodologies that people use to develop these systems.

The Systems development life-cycle is a methodology that also forms the framework for planning and controlling the creation, testing, and delivery of an information system.[1]

The Systems development life-cycle concept acts as the foundation for multiple different development and delivery methodologies, such as the Hardware development life-cycle and Software development life-cycle. While Hardware development life-cycles deal specifically with hardware and Software development life-cycles deal specifically with software, a Systems development life-cycle differs from each in that it can deal with any combination of hardware and software, as a system can be composed of hardware only, software only, or a combination of both.[2]

Overview

A Systems development life cycle (SDLC) is a process that is composed of a number of clearly defined and distinct work phases which are used by an information technology resources, such as systems engineers and systems developers to plan for, design, build, test, and deliver information systems. Like anything that is manufactured on an assembly line, an SDLC aims to produce high quality systems that meet or exceed customer expectations, based on customer requirements, by delivering systems which move through each clearly defined phase, within scheduled time-frames and cost estimates.[3]

Computer systems are complex and often (especially with the recent rise of service-oriented architecture) link multiple traditional systems potentially supplied by different software vendors. To manage this level of complexity, a number of SDLC models or methodologies have been created, such as "waterfall"; "spiral"; "Agile software development"; "rapid prototyping"; "incremental"; and "synchronize and stabilize".[4]

SDLC can be described along a spectrum of agile to iterative to sequential. Anamorphic Development, tend to focus on a form of development that is guided by project scope and adaptive iterations of feature development.

In project management a project can be defined both with a project life cycle (PLC) and an SDLC, during which slightly different activities occur. According to Taylor (2004) "the project life cycle encompasses all the activities of the project, while the systems development life cycle focuses on realizing the product requirements".[5]

SDLC (systems development life cycle) is used during the development of an IT project, it describes the different stages involved in the project from the drawing board, through the completion of the project.

History

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".[6]

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".[6]

Systems development phases

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.

The 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 includes 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:[7]

  • Preliminary Analysis: The objective of phase 1 is to conduct a preliminary analysis, propose alternative solutions, describe costs and benefits and submit a preliminary plan with recommendations.
Conduct the preliminary analysis: in this step, you need to find out the organization's objectives and the nature and scope of the problem under study. Even if a problem refers only to a small segment of the organization itself then you need to find out what the objectives of the organization itself are. Then you need to see how the problem being studied fits in with them.
Propose alternative solutions: In digging into the organization's objectives and specific problems, you may have already covered some solutions. Alternate proposals may come from interviewing employees, clients, suppliers, and/or consultants. You can also study what competitors are doing. With this data, you will have three choices: leave the system as is, improve it, or develop a new system.
Describe the costs and benefits.
  • Systems analysis, requirements definition: Defines project goals into defined functions and operation of the intended application. Analyzes end-user information needs.
  • Development: The real code is written here.
  • Integration and testing: Brings all the pieces together into a special testing environment, then checks for errors, bugs and interoperability.
  • Acceptance, installation, deployment: The final stage of initial development, where the software is put into production and runs actual business.
  • Maintenance: During the maintenance stage of the SDLC, the system is assessed to ensure it does not become obsolete. This is also where changes are made to initial software. It involves continuous evaluation of the system in terms of its performance.
  • Evaluation: Some companies do not view this as an official stage of the SDLC, but is it an important part of the life cycle. Evaluation step is an extension of the Maintenance stage, and may be referred to in some circles as Post-implementation Review. This is where the system that was developed, as well as the entire process, is evaluated. Some of the questions that need to be answered include: does the newly implemented system meet the initial business requirements and objectives? Is the system reliable and fault-tolerant? Does the system function according to the approved functional requirements. In addition to evaluating the software that was released, it is important to assess the effectiveness of the development process. If there are any aspects of the entire process, or certain stages,that management is not satisfied with, this is the time to improve. Evaluation and assessment is a difficult issue. However, the company must reflect on the process and address weaknesses.
  • Disposal Phase: In this phase, plans are developed for discarding system information, hardware and software in making the transition to a new system. The purpose here is to properly move, archive, discard or destroy information, hardware and software that is being replaced, in a matter that prevents any possibility of unauthorized disclosure of sensitive data. The disposal activities ensure proper migration to a new system. Particular emphasis is given to proper preservation and archival of data processed by the previous system. All of this should be done in accordance with the organization's security requirements.[8]

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.[9]

System Investigation

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.[10]

Following are different components of the feasibility study:

System analysis

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.

Design

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 system 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 system in sufficient detail, such that skilled developers and engineers may develop and deliver the system with minimal additional input design.

Environments

Environments are controlled areas where systems developers can build, distribute, install, configure, test, and execute systems that move through the SDLC. Each environment is aligned with different areas of the SDLC and is intended to have specific purposes. Examples of such environments include the:

  • Development environment, where developers can work independently of each other before trying to merge their work with the work of others,
  • Common build environment, where merged work can be built, together, as a combined system,
  • Systems integration testing environment, where basic testing of a system's integration points to other upstream or downstream systems can be tested,
  • User acceptance testing environment, where business stakeholders can test against their original business requirements,
  • Production environment, where systems finally get deployed to, for final use by their intended end users.

The planning for, provisioning, and operating of such environments is known as practice of IT environment management.[11]

Testing

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:

Training and transition

Once a system has been stabilized through adequate testing, the SDLC ensures that proper training on the system is performed or documented before transitioning the system to its support staff and end users.

Training usually covers operational training for those people who will be responsible for supporting the system as well as training for those end users who will be using the system after its delivery to a production operating environment.

After training has been successfully completed, systems engineers and developers transition the system to its final production environment, where it is intended to be used by its end users and supported by its support and operations staff.

Operations and maintenance

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 is the traditional approach (structured) and Object Oriented. Information Engineering includes the traditional system approach, which is also called the Structured Analysis and Design Technique. The Object Oriented approach views the information system as a collection of objects that are integrated with each other to make a full and complete information system.

Evaluation

The final phase of the SDLC is to measure the effectiveness of the application and evaluate potential enhancements.... ""Please, take over control""

Systems analysis and design

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

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:

  • Conceptual model: Conceptual model is the result of object-oriented analysis, it captures concepts in the problem domain. The conceptual model is explicitly chosen to be independent of implementation details, such as concurrency or data storage.
  • Use case: Use case is a description of sequences of events that, taken together, lead to a system doing something useful. Each use case provides one or more scenarios that convey how the system should interact with the users called actors to achieve a specific business goal or function. Use case actors may be end users or other systems. In many circumstances use cases are further elaborated into use case diagrams. Use case diagrams are used to identify the actor (users or other systems) and the processes they perform.
  • System Sequence Diagram: System Sequence diagram (SSD) is a picture that shows, for a particular scenario of a use case, the events that external actors generate, their order, and possible inter-system events.
  • User interface documentations (if applicable): Document that shows and describes the look and feel of the end product's user interface. It is not mandatory to have this, but it helps to visualize the end-product and therefore helps the designer.
  • Relational data model (if applicable): A data model is an abstract model that describes how data is represented and used. If an object database is not used, the relational data model should usually be created before the design, since the strategy chosen for object-relational mapping is an output of the OO design process. However, it is possible to develop the relational data model and the object-oriented design artifacts in parallel, and the growth of an artifact can stimulate the refinement of other artifacts.

Systems development life cycle

Management and control


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.[12]

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.[12]

Work breakdown structured organization

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.[12]

Baselines in the SDLC

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 .[13] Each baseline is considered as a milestone in the SDLC.

  • functional baseline: established after the conceptual design phase.
  • allocated baseline: established after the preliminary design phase.
  • product baseline: established after the detail design and development phase.
  • updated product baseline: established after the production construction phase.

Complementary to SDLC

Complementary software development methods to systems development life cycle (SDLC) are:

Comparison of Methodology Approaches (Post, & Anderson 2006)[14]
SDLC RAD Open source Objects JAD Prototyping End User
Control Formal MIS Weak Standards Joint User 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
Transaction/DSS Transaction Both Both Both DSS DSS DSS
Interface Minimal Minimal Weak Windows Crucial Crucial Crucial
Documentation and training Vital Limited Internal In Objects Limited Weak None
Integrity and security Vital Vital Unknown In Objects Limited Weak Weak
Reusability Limited Some Maybe Vital Limited Weak None

Strengths and weaknesses

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 systems 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:

Strength and Weaknesses of SDLC [14]
Strengths Weaknesses
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.

See also

References

Further reading

  • Blanchard, B. S., & Fabrycky, W. J. (2006) Systems engineering and analysis (4th ed.) New Jersey: Prentice Hall.
  • Cummings, Haag (2006). Management Information Systems for the Information Age. Toronto, McGraw-Hill Ryerson
  • Beynon-Davies P. (2009). Business Information Systems. Palgrave, Basingstoke. ISBN 978-0-230-20368-6
  • Computer World, 2002, Retrieved on June 22, 2006 from the World Wide Web:
  • Management Information Systems, 2005, Retrieved on June 22, 2006 from the World Wide Web:
  • This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.

External links

  • The Agile System Development Lifecycle
  • Pension Benefit Guaranty Corporation – Information Technology Solutions Lifecycle Methodology
  • FSA Life Cycle Framework
  • HHS Enterprise Performance Life Cycle Framework
  • The Open Systems Development Life Cycle
  • System Development Life Cycle Evolution Modeling
  • Zero Deviation Life Cycle
  • Integrated Defense AT&L Life Cycle Management Chart, the U.S. DoD form of this concept.
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.