Systems Analysis and Design
The Big Picture
Systems Analysis and Design
- Systems analysis is the process of studying
an existing system to determine how it works and how it meets
user needs.
- Systems design is the process of developing
a plan for an improved system, based on the results of the systems
analysis.
The Systems Analyst
- The systems analyst performs both analysis and
design. A programmer/analyst also performs the programming.
- A client is the person or organization contracting
to have the work done.
- Users are the people who have contact with the
system, usually employees and customers.
The Systems Development Life Cycle
- Preliminary investigation - determining the
problem.
- Analysis - understanding the existing system.
- Design - planning the new system.
- Development - doing the work to bring the new
system into being.
- Implementation - converting to the new system.
Phase 1: Preliminary Investigation
- The preliminary investigation - often called
the feasibility study, or system survey -
is the initial investigation, a brief study of the problem.
- You must define the nature of the problem, the
scope of the new or revised system, and the objectives
of the project.
Phase 2: Systems Analysis
- In order to understand the existing system, you must gather
all the data about it, then organize and analyze the data.
- Common data sources are written documents, interviews, questionnaires,
observation, and sampling.
- A variety of tools such as data flow diagrams and
decision tables are used to analyze the data.
Phase 3: Systems Design
- Systems design involves designing the new system, and is broken
down into two subphases: preliminary design, and
detailed design.
- Preliminary design often involves alternative plans and often
makes use of devices such as prototyping and CASE
tools.
Prototyping
- A prototype is a limited working system - or
a subset of a system - that is developed quickly so users can
see how the system will work before it is fully developed.
- Prototyping exploits advances in computer technology and uses
powerful high-level software tools.
CASE Tools
- CASE (Computer-Aided Software Engineering) tools go beyond
prototyping to provide an automated means of designing and changing
systems.
- In some CASE tools, data flow diagrams drawn on screen generate
the necessary code and databases.
Detail Design
- Every facet of the system is considered in detail.
- Normally, the following parts of the system are considered:
output requirements, input requirements, files and databases,
system processing, system controls, and backup.
- A systems flowchart is used to show the flow
of data in the new system.
Phase 4: Systems Development
- Scheduling of the development is often accomplished
using Gantt charts, bar charts used to depict schedule
deadlines and milestones.
- Programming is begun after detailed design specifications
are established.
- Testing is done on the program to ensure it
does what it is supposed to do.
Phase 5: Implementation
- Implementation of the system includes the following activities:
- Training of users via manuals, on-line help,
and hands-on training.
- Equipment, file, and system conversion to accommodate
the new system.
- Evaluation of the system by the systems analyst
and the client organization.
- Ongoing maintenance of the system, making revisions
and additions to fix problems and add enhancements.