Requirement Engineering Process: Feasibility
Studies, Requirements elicitation and analysis
The Systems Development Life Cycle (SDLC),
or Software Development Life Cycle in
systems engineering, information systems and software engineering, is the
process of creating or altering systems, and the models and methodologies that
people use to develop these systems. The concept generally refers to computer
or information 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 Development Life Cycle (SDLC),
or Software Development Life Cycle in
systems engineering, information systems and software engineering, is the
process of creating or altering systems, and the models and methodologies that
people use to develop these systems. The concept generally refers to computer
or information 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.
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.
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. 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
·
Project planning, feasibility
study: Establishes a high-level view of the intended project and determines its goals.
·
Systems analysis,
requirements definition: Refines project goals into defined functions and operation of the intended application.
Analyzes end-user information needs.
·
Systems design: Describes desired features
and operations in detail, including screen layouts, business rules, process diagrams, pseudocode and other
documentation.
·
Implementation: 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: What happens during the
rest of the software's life: changes, correction, additions, moves to a different computing platform and more. This,
the least glamorous and perhaps most important step of all, goes on seemingly
forever.
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.
Requirements
analysis sometimes requires individuals/teams from client as well as service
provider sides to get detailed and accurate requirements; often there has to be
a lot of communication to and from to understand these requirements.
Requirement gathering is the most crucial aspect as many times communication
gaps arise in this phase and this leads to validation errors and bugs in the
software program.
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 software features in detail, and generally
include functional hierarchy diagrams, screen layout diagrams, tables of
business rules, business process diagrams, pseudocode, 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.
Implementation
Modular
and subsystem programming code will be accomplished during this stage. Unit
testing and module testing are done in this stage by the developers. This stage
is intermingled with the next in that individual modules will need testing
before integration to the main project.
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:
·
Defect testing
·
Path testing
·
Data set testing
·
Unit testing
·
System testing
·
Integration testing
·
Black box testing
·
White box testing
·
Regression testing
·
Automation testing
·
User acceptance testing
·
Performance testing
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, which will require system updates.
SYSTEMS ANALYSIS AND DESIGN
The Systems Analysis and Design (SAD) is
the process of developing Information Systems (IS) that effectively use of
hardware, software, data, process, and people to support the company’s business
objectives.
SYSTEMS DEVELOPMENT LIFE CYCLE TOPICS
Management and control
SDLC
Phases Related to Management Controls.
The
Systems Development Life Cycle (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.
Work breakdown structured organization
Work
Breakdown Structure.
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 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
.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:
·
Open Source Development
· End-user development
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