Information Technology Reference
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around the data. Each process transforms a part of the system data in some
way. When all of the processes are executed, the system data is transformed as
desired. The data flows from one process to another until information is
extracted and presented as output of the system. This model is presently
referred to as process modeling. During requirements analysis, we model the
existing processes and during design, we model the proposed system.
3.
Entity Behavior Modeling—It is modeling the sequence of operations in the
system. Events in the processes impact and transform the entities. We model
each event and the behavior of the impacted entities and the sequence of events
in a process from the first input to the final output, diagrammatically in this
modeling.
SSADM, from the day it was implemented, held its place among the other various
software development methodologies. The original model was modified by many
organizations and researchers. I would rather go to the extent of saying that all other
methodologies that have emerged since, still contain a streak of SSADM in them. In
the spiral model and the iterative model, each increment/iteration is still a waterfall
model. The logical data modeling which later transformed into ERD (Entity Rela-
tionship Diagram) is the only way to model system data even today. The process
standards like the ISO 9000 and CMMI
implement the philosophy of SSADM.
IEEE also followed the SSADM model in defining the software engineering stan-
dards when they released the first set in 1988. The agile methods denounce the heavy
reliance of SSADM on documentation but still implement the waterfall model in
each of the iterations. In outsourced development SSADM is still significantly uti-
lized to drive software development contracts.
13.2.9 Requirements Engineering and Management in SSADM
SSADM accorded significant importance to the aspect of requirements engineering
and management by designating a separate phase for this activity. During this
phase, the activities of elicitation, gathering, analysis and establishment are carried
out. The deliverable of this phase is the Requirements Specifications Document.
The technique of logical data modeling to model the system data was the
originally suggested technique but now, ERDs are being used to model data. The
technique of dataflow diagrams is used to model process flow in SSADM.
13.2.10 ER Diagrams
Data modeling deals with establishing the relationship between various data
entities in the system. In any information transaction, data is transmitted between
entities. Let us take a simplified purchase transaction:
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