<s>
A	O
data	O
structure	B-Language
diagram	I-Language
(	O
DSD	O
)	O
is	O
the	O
visual	O
representation	O
of	O
a	O
certain	O
kind	O
of	O
data	B-Application
model	I-Application
that	O
contains	O
entities	O
,	O
their	O
relationships	B-Architecture
,	O
and	O
the	O
constraints	O
that	O
are	O
placed	O
on	O
them	O
.	O
</s>
<s>
The	O
arrow	O
symbol	O
represents	O
relationships	B-Architecture
.	O
</s>
<s>
Data	O
structure	B-Language
diagrams	I-Language
are	O
most	O
useful	O
for	O
documenting	O
complex	O
data	O
entities	O
.	O
</s>
<s>
Data	O
Structure	B-Language
Diagram	I-Language
is	O
a	O
diagram	O
type	O
that	O
is	O
used	O
to	O
depict	O
the	O
structure	O
of	O
data	O
elements	O
in	O
the	O
data	B-Application
dictionary	I-Application
.	O
</s>
<s>
The	O
data	O
structure	B-Language
diagram	I-Language
is	O
a	O
graphical	O
alternative	O
to	O
the	O
composition	O
specifications	O
within	O
such	O
data	B-Application
dictionary	I-Application
entries	O
.	O
</s>
<s>
The	O
data	O
structure	B-Language
diagrams	I-Language
is	O
a	O
predecessor	O
of	O
the	O
entity	B-Architecture
–	I-Architecture
relationship	I-Architecture
model	I-Architecture
(	O
E	O
–	O
R	O
model	O
)	O
.	O
</s>
<s>
In	O
DSDs	O
,	O
attributes	O
are	O
specified	O
inside	O
the	O
entity	O
boxes	O
rather	O
than	O
outside	O
of	O
them	O
,	O
while	O
relationships	B-Architecture
are	O
drawn	O
as	O
boxes	O
composed	O
of	O
attributes	O
which	O
specify	O
the	O
constraints	O
that	O
bind	O
entities	O
together	O
.	O
</s>
<s>
DSDs	O
differ	O
from	O
the	O
E	O
–	O
R	O
model	O
in	O
that	O
the	O
E	O
–	O
R	O
model	O
focuses	O
on	O
the	O
relationships	B-Architecture
between	O
different	O
entities	O
,	O
whereas	O
DSDs	O
focus	O
on	O
the	O
relationships	B-Architecture
of	O
the	O
elements	O
within	O
an	O
entity	O
.	O
</s>
<s>
There	O
are	O
several	O
styles	O
for	O
representing	O
data	O
structure	B-Language
diagrams	I-Language
,	O
with	O
the	O
notable	O
difference	O
in	O
the	O
manner	O
of	O
defining	O
cardinality	B-Application
.	O
</s>
<s>
The	O
choices	O
are	O
between	O
arrow	O
heads	O
,	O
inverted	O
arrow	O
heads	O
(	O
crow	B-Architecture
's	I-Architecture
feet	I-Architecture
)	O
,	O
or	O
numerical	O
representation	O
of	O
the	O
cardinality	B-Application
.	O
</s>
<s>
A	O
Bachman	B-Application
diagram	I-Application
is	O
a	O
certain	O
type	O
of	O
data	O
structure	B-Language
diagram	I-Language
,	O
and	O
is	O
used	O
to	O
design	O
the	O
data	O
with	O
a	O
network	O
or	O
relational	O
"	O
logical	O
"	O
model	O
,	O
separating	O
the	O
data	B-Application
model	I-Application
from	O
the	O
way	O
the	O
data	O
is	O
stored	O
in	O
the	O
system	O
.	O
</s>
<s>
In	O
a	O
relational	B-Architecture
model	I-Architecture
,	O
a	O
relation	O
is	O
the	O
cohesion	O
of	O
attributes	O
that	O
are	O
fully	O
and	O
not	O
of	O
every	O
key	O
in	O
that	O
relation	O
.	O
</s>
<s>
On	O
the	O
edge	O
of	O
each	O
line	O
,	O
arrows	O
indicate	O
the	O
cardinality	B-Application
.	O
</s>
