A
data
dictionary
lists
all
data
items
appearing
in
the
DFD
model
of
a
system
.
The
data
items
listed
include
all
data
flows
and
the
contents
of
all
data
stores
appearing
on
the
DFDs
in
the
of
a
system
.
A
data
dictionary
lists
the
purpose
of
all
data
items
and
the
definition
of
all
composite
data
items
in
terms
of
their
component
data
items
.
For
example
,
a
data
dictionary
entry
may
that
the
data
grossPay
consists
of
the
components
regularPay
and
overtimePay
.
grossPay
=
+
For
the
smallest
units
of
data
items
,
the
data
dictionary
lists
their
name
and
their
type
.
Composite
data
items
can
be
defined
in
terms
of
primitive
data
items
using
the
following
data
definition
operators
:
+
:
denotes
composition
of
two
data
items
,
e
.
g
.
a
+
b
represents
data
a
and
b
.
[
,
,
]
:
represents
selection
,
i
.
e
.
any
one
of
the
data
items
listed
in
the
brackets
can
occur
.
For
example
,
[
a
,
b
]
represents
either
a
occurs
or
b
occurs
.
(
)
:
the
contents
inside
the
bracket
represent
optional
data
which
may
or
may
not
.
e
.
g
.
a
+
(
b
)
either
a
occurs
or
a
+
b
occurs
.
{
}
:
represents
iterative
data
definition
,
e
.
g
.
{
name
}
5
represents
five
name
data
.
{
name
}
*
represents
zero
or
more
instances
of
name
data
.
=
:
represents
equivalence
,
e
.
g
.
a
=
b
+
c
means
that
a
represents
b
and
c
.
/
*
*
/
:
Anything
appearing
within
/
*
and
*
/
is
considered
as
a
comment
.
Example
1
:
Tic
-
Tac
-
Toe
Tic
-
tac
-
toe
is
a
computer
game
in
which
a
human
player
and
the
computer
make
alternative
moves
on
a
3×3
square
.
A
move
consists
of
marking
previously
unmarked
square
.
The
player
who
first
places
three
consecutive
marks
along
a
straight
line
on
the
square
(
i
.
e
.
along
a
row
,
column
,
or
diagonal
)
wins
the
game
.
As
as
either
the
human
player
or
the
computer
wins
,
a
message
congratulating
the
winner
should
be
displayed
.
If
neither
player
manages
to
get
consecutive
marks
along
a
straight
,
but
all
the
squares
on
the
board
are
filled
up
,
then
the
game
is
drawn
.
The
computer
always
tries
to
win
a
game
.
Specific
Instructional
Objectives
At
the
of
this
lesson
the
student
will
be
able
to
:
?
Identify
the
activities
carried
out
during
the
structured
analysis
phase
.
?
what
a
DFD
is
.
?
Explain
why
constructing
DFDs
are
important
in
arriving
at
a
good
software
design
.
?
what
a
data
dictionary
is
.
?
Explain
the
importance
of
data
dictionary
.
?
Identify
whether
a
DFD
is
balanced
.
Structured
Analysis
Structured
analysis
is
used
to
carry
out
the
top
-
down
of
a
set
of
high
-
level
functions
depicted
in
the
problem
description
and
to
represent
them
graphically
.
During
analysis
,
functional
decomposition
of
the
system
is
achieved
.
That
is
,
each
function
that
the
system
performs
is
analyzed
and
decomposed
into
more
detailed
functions
.
Structured
analysis
technique
is
based
on
the
following
underlying
principles
:
?
Top
-
down
approach
.
?
Divide
and
conquer
principle
.
Each
function
is
decomposed
independently
.
?
Graphical
representation
of
the
analysis
results
using
Data
Flow
Diagrams
(
DFDs
)
.