<s>
A	O
database	B-Application
server	I-Application
is	O
a	O
server	O
which	O
uses	O
a	O
database	B-Application
application	I-Application
that	O
provides	O
database	O
services	O
to	O
other	O
computer	O
programs	O
or	O
to	O
computers	O
,	O
as	O
defined	O
by	O
the	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
model	I-Operating_System
.	O
</s>
<s>
Database	O
management	O
systems	O
(	O
DBMSs	O
)	O
frequently	O
provide	O
database-server	O
functionality	O
,	O
and	O
some	O
database	O
management	O
systems	O
(	O
such	O
as	O
MySQL	B-Application
)	O
rely	O
exclusively	O
on	O
the	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
model	I-Operating_System
for	O
database	O
access	O
(	O
while	O
others	O
,	O
like	O
SQLite	B-Language
,	O
are	O
meant	O
for	O
use	O
as	O
an	O
embedded	B-Application
database	I-Application
)	O
.	O
</s>
<s>
Users	O
access	O
a	O
database	B-Application
server	I-Application
either	O
through	O
a	O
"	O
front	B-Architecture
end	I-Architecture
"	O
running	O
on	O
the	O
user	O
's	O
computerwhich	O
displays	O
requested	O
dataor	O
through	O
the	O
"	O
back	B-Architecture
end	I-Architecture
"	O
,	O
which	O
runs	O
on	O
the	O
server	O
and	O
handles	O
tasks	O
such	O
as	O
data	O
analysis	O
and	O
storage	O
.	O
</s>
<s>
In	O
a	O
master	B-Operating_System
–	I-Operating_System
slave	I-Operating_System
model	B-Language
,	O
database	O
master	O
servers	O
are	O
central	O
and	O
primary	O
locations	O
of	O
data	O
while	O
database	B-Operating_System
slave	I-Operating_System
servers	O
are	O
synchronized	O
backups	O
of	O
the	O
master	O
acting	O
as	O
proxies	B-Application
.	O
</s>
<s>
Most	O
database	B-Application
applications	I-Application
respond	O
to	O
a	O
query	B-Language
language	I-Language
.	O
</s>
<s>
Each	O
database	O
understands	O
its	O
query	B-Language
language	I-Language
and	O
converts	O
each	O
submitted	O
query	O
to	O
server-readable	O
form	O
and	O
executes	O
it	O
to	O
retrieve	O
results	O
.	O
</s>
<s>
Examples	O
of	O
proprietary	O
database	B-Application
applications	I-Application
include	O
Oracle	B-General_Concept
,	O
IBM	B-Application
Db2	I-Application
,	O
Informix	B-Application
,	O
and	O
Microsoft	B-Application
SQL	I-Application
Server	I-Application
.	O
</s>
<s>
Examples	O
of	O
free	B-Application
software	I-Application
database	B-Application
applications	I-Application
include	O
PostgreSQL	B-Application
;	O
and	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
Licence	I-License
include	O
Ingres	B-Application
and	O
MySQL	B-Application
.	O
</s>
<s>
The	O
SQL	B-Language
(	O
Structured	B-Language
Query	I-Language
Language	I-Language
)	O
query	B-Language
language	I-Language
is	O
more	O
or	O
less	O
the	O
same	O
on	O
all	O
relational	B-Application
database	I-Application
applications	O
.	O
</s>
<s>
For	O
clarification	O
,	O
a	O
database	B-Application
server	I-Application
is	O
simply	O
a	O
server	O
that	O
maintains	O
services	O
related	O
to	O
clients	O
via	O
database	B-Application
applications	I-Application
.	O
</s>
<s>
DB-Engines	B-Application
lists	O
over	O
300	O
DBMSs	O
in	O
its	O
ranking	O
.	O
</s>
<s>
Bachman	O
introduced	O
Data	B-Application
Structure	I-Application
Diagrams	I-Application
(	O
DSDs	O
)	O
as	O
a	O
means	O
to	O
graphically	O
represent	O
data	O
.	O
</s>
<s>
Codd	O
proposed	O
the	O
"	O
relational	O
view	O
"	O
of	O
data	O
which	O
later	O
evolved	O
into	O
the	O
Relational	B-Architecture
Model	I-Architecture
which	O
most	O
databases	O
use	O
today	O
.	O
</s>
<s>
In	O
1971	O
,	O
the	O
Database	O
Task	O
Report	O
Group	O
of	O
CODASYL	B-Language
(	O
the	O
driving	O
force	O
behind	O
the	O
development	O
of	O
the	O
programming	O
language	O
COBOL	B-Application
)	O
first	O
proposed	O
a	O
"	O
data	O
description	O
language	O
for	O
describing	O
a	O
database	O
,	O
a	O
data	O
description	O
language	O
for	O
describing	O
that	O
part	O
of	O
the	O
data	O
base	O
known	O
to	O
a	O
program	O
,	O
and	O
a	O
data	O
manipulation	O
language.	O
"	O
</s>
<s>
Most	O
of	O
the	O
research	O
and	O
development	O
of	O
databases	O
focused	O
on	O
the	O
relational	B-Architecture
model	I-Architecture
during	O
the	O
1970s	O
.	O
</s>
<s>
In	O
1975	O
,	O
Bachman	O
demonstrated	O
how	O
the	O
relational	B-Architecture
model	I-Architecture
and	O
the	O
data	O
structure	O
set	O
were	O
similar	O
and	O
"	O
congruent	O
"	O
ways	O
of	O
structuring	O
data	O
while	O
working	O
for	O
Honeywell	O
.	O
</s>
<s>
The	O
entity	B-Architecture
–	I-Architecture
relationship	I-Architecture
model	I-Architecture
was	O
first	O
proposed	O
in	O
its	O
current	O
form	O
by	O
Peter	O
Chen	O
in	O
1976	O
while	O
he	O
was	O
conducting	O
research	O
at	O
MIT	O
.	O
</s>
<s>
This	O
model	B-Language
became	O
the	O
most	O
frequently	O
used	O
model	B-Language
to	O
describe	O
relational	B-Application
databases	I-Application
.	O
</s>
<s>
Chen	O
was	O
able	O
to	O
propose	O
a	O
model	B-Language
that	O
was	O
superior	O
to	O
the	O
navigational	O
model	B-Language
and	O
was	O
more	O
applicable	O
to	O
the	O
"	O
real	O
world	O
"	O
than	O
the	O
relational	B-Architecture
model	I-Architecture
proposed	O
by	O
Codd	O
.	O
</s>
