<s>
A	O
logical	B-Application
data	I-Application
model	I-Application
or	O
logical	B-Application
schema	I-Application
is	O
a	O
data	B-Application
model	I-Application
of	O
a	O
specific	O
problem	O
domain	O
expressed	O
independently	O
of	O
a	O
particular	O
database	O
management	O
product	O
or	O
storage	O
technology	O
(	O
physical	B-Application
data	I-Application
model	I-Application
)	O
but	O
in	O
terms	O
of	O
data	O
structures	O
such	O
as	O
relational	O
tables	O
and	O
columns	O
,	O
object-oriented	B-Application
classes	O
,	O
or	O
XML	O
tags	O
.	O
</s>
<s>
This	O
is	O
as	O
opposed	O
to	O
a	O
conceptual	B-Application
data	I-Application
model	I-Application
,	O
which	O
describes	O
the	O
semantics	O
of	O
an	O
organization	O
without	O
reference	O
to	O
technology	O
.	O
</s>
<s>
Logical	B-Application
data	I-Application
models	I-Application
represent	O
the	O
abstract	O
structure	O
of	O
a	O
domain	O
of	O
information	O
.	O
</s>
<s>
Once	O
validated	O
and	O
approved	O
,	O
the	O
logical	B-Application
data	I-Application
model	I-Application
can	O
become	O
the	O
basis	O
of	O
a	O
physical	B-Application
data	I-Application
model	I-Application
and	O
form	O
the	O
design	O
of	O
a	O
database	O
.	O
</s>
<s>
Logical	B-Application
data	I-Application
models	I-Application
should	O
be	O
based	O
on	O
the	O
structures	O
identified	O
in	O
a	O
preceding	O
conceptual	B-Application
data	I-Application
model	I-Application
,	O
since	O
this	O
describes	O
the	O
semantics	O
of	O
the	O
information	O
context	O
,	O
which	O
the	O
logical	O
model	O
should	O
also	O
reflect	O
.	O
</s>
<s>
Even	O
so	O
,	O
since	O
the	O
logical	B-Application
data	I-Application
model	I-Application
anticipates	O
implementation	O
on	O
a	O
specific	O
computing	O
system	O
,	O
the	O
content	O
of	O
the	O
logical	B-Application
data	I-Application
model	I-Application
is	O
adjusted	O
to	O
achieve	O
certain	O
efficiencies	O
.	O
</s>
<s>
The	O
term	O
'	O
Logical	B-Application
Data	I-Application
Model	I-Application
 '	O
is	O
sometimes	O
used	O
as	O
a	O
synonym	B-Application
of	O
'	O
domain	B-Application
model	I-Application
 '	O
or	O
as	O
an	O
alternative	O
to	O
the	O
domain	B-Application
model	I-Application
.	O
</s>
<s>
While	O
the	O
two	O
concepts	O
are	O
closely	O
related	O
,	O
and	O
have	O
overlapping	O
goals	O
,	O
a	O
domain	B-Application
model	I-Application
is	O
more	O
focused	O
on	O
capturing	O
the	O
concepts	O
in	O
the	O
problem	O
domain	O
rather	O
than	O
the	O
structure	O
of	O
the	O
data	O
associated	O
with	O
that	O
domain	O
.	O
</s>
<s>
When	O
ANSI	O
first	O
laid	O
out	O
the	O
idea	O
of	O
a	O
logical	B-Application
schema	I-Application
in	O
1975	O
,	O
the	O
choices	O
were	O
hierarchical	O
and	O
network	O
.	O
</s>
<s>
The	O
relational	B-Architecture
model	I-Architecture
–	O
where	O
data	O
is	O
described	O
in	O
terms	O
of	O
tables	O
and	O
columns	O
–	O
had	O
just	O
been	O
recognized	O
as	O
a	O
data	O
organization	O
theory	O
but	O
no	O
software	O
existed	O
to	O
support	O
that	O
approach	O
.	O
</s>
<s>
Since	O
that	O
time	O
,	O
an	O
object-oriented	B-Application
approach	O
to	O
data	O
modelling	O
–	O
where	O
data	O
is	O
described	O
in	O
terms	O
of	O
classes	O
,	O
attributes	O
,	O
and	O
associations	O
–	O
has	O
also	O
been	O
introduced	O
.	O
</s>
<s>
A	O
logical	B-Application
data	I-Application
model	I-Application
is	O
sometimes	O
incorrectly	O
called	O
a	O
physical	B-Application
data	I-Application
model	I-Application
,	O
which	O
is	O
not	O
what	O
the	O
ANSI	O
people	O
had	O
in	O
mind	O
.	O
</s>
<s>
Conceptual	O
,	O
logical	O
and	O
physical	B-Application
data	I-Application
models	I-Application
are	O
very	O
different	O
in	O
their	O
objectives	O
,	O
goals	O
and	O
content	O
.	O
</s>
<s>
Conceptual	B-Application
Data	I-Application
Model	I-Application
(	O
CDM	O
)	O
Logical	B-Application
Data	I-Application
Model	I-Application
(	O
LDM	O
)	O
Physical	B-Application
Data	I-Application
Model	I-Application
(	O
PDM	O
)	O
Includes	O
high-level	O
data	O
constructs	O
Includes	O
entities	O
(	O
tables	O
)	O
,	O
attributes	O
(	O
columns/fields	O
)	O
and	O
relationships	O
(	O
keys	O
)	O
Includes	O
tables	O
,	O
columns	O
,	O
keys	O
,	O
data	O
types	O
,	O
validation	O
rules	O
,	O
database	O
triggers	O
,	O
stored	O
procedures	O
,	O
domains	O
,	O
and	O
access	O
constraints	O
Non-technical	O
names	O
,	O
so	O
that	O
executives	O
and	O
managers	O
at	O
all	O
levels	O
can	O
understand	O
the	O
data	O
basis	O
of	O
Architectural	O
Description	O
Uses	O
business	O
names	O
for	O
entities	O
&	O
attributes	O
Uses	O
more	O
defined	O
and	O
less	O
generic	O
specific	O
names	O
for	O
tables	O
and	O
columns	O
,	O
such	O
as	O
abbreviated	O
column	O
names	O
,	O
limited	O
by	O
the	O
database	O
management	O
system	O
(	O
DBMS	O
)	O
and	O
any	O
company	O
defined	O
standards	O
Uses	O
general	O
high-level	O
data	O
constructs	O
from	O
which	O
Architectural	O
Descriptions	O
are	O
created	O
in	O
non-technical	O
terms	O
Is	O
independent	O
of	O
technology	O
(	O
platform	O
,	O
DBMS	O
)	O
Includes	O
primary	O
keys	O
and	O
indices	O
for	O
fast	O
data	O
access	O
.	O
</s>
