7.3: Systems Development Life Cycle
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The Systems Development Life Cycle (SDLC) was first developed in the 1960s to manage large software projects running on corporate mainframes. This approach to software development is structured and risk averse, designed to manage large projects that include multiple programmers and systems. It requires a clear, upfront understanding of what the software is supposed to do and is not amenable to design changes. This approach is roughly similar to an assembly line process, where it is clear to all stakeholders what the end product should do and that major changes are difficult and costly to implement. The following is the process of the SDLC. Various definitions of the SDLC methodology exist, but most contain the following phases.
- Preliminary Analysis . A request for a replacement or new system is first reviewed. The review includes questions such as: What is the problem-to-be-solved? Is creating a solution possible? What alternatives exist? What is currently being done about it? Is this project a good fit for our organization? This process is referred to as a needs analysis. After addressing these questions, a feasibility study is launched (this will be discussed later). This step is important in determining if the project should be initiated.
- System Analysis. In this phase one or more system analysts work with different stakeholder groups to determine the specific requirements for the new system. No programming is done in this step. Instead, procedures are documented, key players/users are interviewed, and data requirements are developed in order to get an overall impression of exactly what the system is supposed to do. The result of this phase is a system requirements document and may be done by someone with a title of Systems Analyst.
- System Design. In this phase, a designer takes the system requirements document created in the previous phase and develops the specific technical details required for the system. It is in this phase that the business requirements are translated into specific technical requirements. The design for the user interface, database, data inputs and outputs, and reporting are developed here. The result of this phase is a system design document. This document will have everything a programmer needs to actually create the system and may be done by someone with a title of Systems Analyst, Developer, or Systems Architect, based on the scale of the project.
- Programming. The code finally gets written in the programming phase. Using the system design document as a guide, programmers develop the software. The result of this phase is an initial working program that meets the requirements specified in the system analysis phase and the design developed in the system design phase. These tasks are done by persons with titles such as Developer, Software Engineer, Programmer, or Coder.
- Testing. In the testing phase the software program developed in the programming phase is put through a series of structured tests. The first is a unit test, which evaluates individual parts of the code for errors or bugs. This is followed by a system test in which the different components of the system are tested to ensure that they work together properly. Finally, the user acceptance test allows those that will be using the software to test the system to ensure that it meets their standards. Any bugs, errors, or problems found during testing are resolved and then the software is tested again. These tasks are done by persons with titles such as Tester, Testing Analyst, or Quality Assurance.
- Implementation. Once the new system is developed and tested, it has to be implemented in the organization. This phase includes training the users, providing documentation, and data conversion from the previous system to the new system. Implementation can take many forms, depending on the type of system, the number and type of users, and how urgent it is that the system becomes operational. These different forms of implementation are covered later in the chapter.
- Maintenance. This final phase takes place once the implementation phase is complete. In the maintenance phase the system has a structured support process in place. Reported bugs are fixed and requests for new features are evaluated and implemented. Also, system updates and backups of the software are made for each new version of the program. Since maintenance is normally an Operating Expense (OPEX) while much of development is a Capital Expense (CAPEX), funds normally come out of different budgets or cost centers.
The following table summarizes the important tasks in the stages of the SDLC and highlights the main deliverables from each task.
| Stage | Tasks | Deliverables |
|---|---|---|
| Preliminary Analysis | Problem Definition Scope and Objectives Data Gathering Risk Assessment Feasibility Analysis | Project Charter Feasibility Study |
| Systems Analysis | Data Gathering Systems Modeling User Requirements Definition | User Requirements Specification |
| Systems Design | Make or Buy Decision Physical Systems Design Technical Design | Detailed Systems Specification |
| Programming & Testing | Programming and testing Platform Implementation | Production System |
| Systems Implementation | User Training Data Conversion Systems Conversion Post-Implementation Review | Live System |
| Systems Maintenance | Fix system “bugs” System enhancement | Working System |
The SDLC methodology is sometimes referred to as the waterfall methodology to represent how each step is a separate part of the process. Only when one step is completed can another step begin. After each step an organization must decide when to move to the next step. This methodology has been criticized for being quite rigid, allowing movement in only one direction, namely, forward in the cycle. For example, changes to the requirements are not allowed once the process has begun. No software is available until after the programming phase.
Again, SDLC was developed for large, structured projects. Projects using SDLC can sometimes take months or years to complete. Because of its inflexibility and the availability of new programming techniques and tools, many other software development methodologies have been developed. Many of these retain some of the underlying concepts of SDLC, but are not as rigid. Other development approaches are explored in the next section