System design

1. SYSTEM DESIGN

2. OVERVIEW ON SYSTEM DESIGN
• Systems design is the process of defining the architecture,
components, modules, interfaces, and data for a system to satisfy
specified requirements. Systems design could be seen as the
application of systems theory to product development. There is
some overlap with the disciplines of systems analysis, systems
architecture and systems engineering.
• Systems design is therefore the process of defining and
developing systems to satisfy specified requirements of the user.

3. WHAT DOES SYSTEM DESIGN MEAN?
• System design is the process of defining the elements of a
system such as the architecture, modules and components, the
different interfaces of those components and the data that goes
through that system. It is meant to satisfy specific needs and
requirements of a business or organization through the
engineering of a coherent and well-running system.

4. SYSTEM DESIGN EXPLAINED IN MORE
DETAIL
• Systems design implies a systematic approach to the design of
a system. It may take a bottom-up or top-down approach, but
either way the process is systematic wherein it takes into
account all related variables of the system that needs to be
created—from the architecture, to the required hardware and
software, right down to the data and how it travels and
transforms throughout its travel through the system. Systems
design then overlaps with systems analysis, systems
engineering and systems architecture.

5. SSADM - STRUCTURED SYSTEMS ANALYSIS AND
DESIGN METHOD
• Short for Structured Systems Analysis and Design Method, a set
of standards developed in the early 1980s for systems analysis
and application design widely used for government computing
projects in the United Kingdom. SSADM uses a combination of
text and diagrams throughout the whole life cycle of a
systemdesign, from the initial design idea to the actual physical
design of the application.

6. CONTINUATION
• SSADM uses a combination of three techniques:
• Logical Data Modeling -- the process of identifying, modeling and
documenting the data requirements of the system being designed.
The data is separated into entities (things about which a business
needs to record information) and relationships(the associations
between the entities.
• Data Flow Modeling -- the process of identifying, modeling and
documenting how data moves around an information system. Data
Flow Modeling examines processes (activities that transform data from
one form to another), data stores (the holding areas for data), external
entities (what sends data into a system or receives data from a system,
and data flows(routes by which data can flow).
• Entity Behavior Modeling -- the process of identifying, modeling and
documenting the events that affect each entity and the sequence in

7. SSADM application development projects are divided into five modules that are further
broken down into a hierarchy of stages, steps and tasks:
Feasibility Study-- the business area is analyzed to determine whether a system can cost
effectively support the business requirements.
Requirements Analysis-- the requirements of the system to be developed are identified and
the current business environment is modeled in terms of the processes carried out and the
data structures involved.
Requirements Specification-- detailed functional and non-functional requirements are
identified and new techniques are introduced to define the required processing and data
structures.
Logical System Specification-- technical systems options are produced and the logical
design of update and enquiry processing and system dialogues.
Physical Design -- a physical database design and a set of program specifications are
created using the logical system specification and technical system specification.
Unlike rapid application development, which conducts steps in parallel, SSADM builds each
step on the work that was prescribed in the previous step with no deviation from the model.
Because of the rigid structure of the methodology, SSADM is praised for its control over
projects and its ability to develop better quality systems.