15
2. An entity is in second
normal form (2NF)
if it is already in 1NF and if the values
of all nonprimary key attributes are dependent on the full primary key—not
just
part
of
it.
Any
nonkey
attributes
that
are
dependent
on
only
part
of
the
primary
key should be moved to any entity where that partial key is actually the full key.
This may require creating a new entity and relationship on the model.
3. An entity
is
in
third
normal
form
(3NF)
if
it
is already
in 2NF and
if the
values
of
its
nonprimary
key
attributes
are
not
dependent
on
any
other
non-primary key
attributes.
Any
nonkey
attributes
that
are
dependent
on
other
nonkey
attributes
must be moved or deleted. Again, new entities and relationships may have to be
added to the data model.
2.1.4 Data Flow Diagram
Data
Flow
Diagram
is
essential
in
structuring
the
flow
of
the
data
throughout
the
system. More about Data Flow Diagram is further explained below.
2.1.4.1 DFD Definition
Process
modeling
is
a
technique
used
in
organizing
and
documenting
a
data
flow
through a system’s processes.
A
data
flow diagram (DFD)
is software
tools
used
in software development
in order
to displays the flow of data through system and the work or processing done by that
system. Nowadays,
DFD
used commonly by system analyst to know
how the data
flow
through
the
system.
This
tool
helps
most
system
analyst
to
know
the
data
flow
through
the system is correct or not.
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