<s>
A	O
database	B-General_Concept
refactoring	I-General_Concept
is	O
a	O
simple	O
change	O
to	O
a	O
database	B-Application
schema	I-Application
that	O
improves	O
its	O
design	O
while	O
retaining	O
both	O
its	O
behavioral	O
and	O
informational	O
semantics	O
.	O
</s>
<s>
Database	B-General_Concept
refactoring	I-General_Concept
does	O
not	O
change	O
the	O
way	O
data	O
is	O
interpreted	O
or	O
used	O
and	O
does	O
not	O
fix	O
bugs	B-Error_Name
or	O
add	O
new	O
functionality	O
.	O
</s>
<s>
A	O
database	B-General_Concept
refactoring	I-General_Concept
is	O
conceptually	O
more	O
difficult	O
than	O
a	O
code	O
refactoring	O
;	O
code	O
refactorings	O
only	O
need	O
to	O
maintain	O
behavioral	O
semantics	O
while	O
database	B-General_Concept
refactorings	I-General_Concept
also	O
must	O
maintain	O
informational	O
semantics	O
.	O
</s>
<s>
A	O
database	B-Application
schema	I-Application
is	O
typically	O
refactored	O
for	O
one	O
of	O
several	O
reasons	O
:	O
</s>
<s>
To	O
develop	O
the	O
schema	B-Application
in	O
an	O
evolutionary	O
manner	O
in	O
parallel	O
with	O
the	O
evolutionary	O
design	O
of	O
the	O
rest	O
of	O
the	O
system	O
.	O
</s>
<s>
To	O
fix	O
design	O
problems	O
with	O
an	O
existing	O
legacy	O
database	B-Application
schema	I-Application
.	O
</s>
<s>
Database	B-General_Concept
refactorings	I-General_Concept
are	O
often	O
motivated	O
by	O
the	O
desire	O
for	O
database	B-Application
normalization	I-Application
of	O
an	O
existing	O
production	O
database	O
,	O
typically	O
to	O
"	O
clean	O
up	O
"	O
the	O
design	O
of	O
the	O
database	O
.	O
</s>
<s>
In	O
2006	O
Scott	O
Ambler	O
,	O
Pramod	O
Sadalage	O
describe	O
the	O
following	O
categories	O
of	O
database	B-General_Concept
refactoring	I-General_Concept
:	O
</s>
<s>
A	O
change	O
to	O
the	O
table	O
structure	O
of	O
your	O
database	B-Application
schema	I-Application
.	O
</s>
<s>
A	O
change	O
which	O
changes	O
the	O
semantics	O
of	O
your	O
database	B-Application
schema	I-Application
by	O
adding	O
new	O
elements	O
to	O
it	O
or	O
by	O
modifying	O
existing	O
elements	O
.	O
</s>
<s>
In	O
2019	O
Vladislav	O
Struzik	O
supplemented	O
the	O
categories	O
of	O
database	B-General_Concept
refactoring	I-General_Concept
with	O
a	O
new	O
one	O
:	O
</s>
<s>
Methods	O
of	O
the	O
Access	O
Refactoring	O
category	O
:	O
Change	O
Authentication	O
Attributes	O
;	O
Revoke	O
Authorization	O
Privileges	O
;	O
Grant	O
Authorization	O
Privileges	O
;	O
Extract	O
Database	B-Application
Schema	I-Application
;	O
Merge	O
Database	B-Application
Schemas	I-Application
.	O
</s>
<s>
The	O
process	O
of	O
database	B-General_Concept
refactoring	I-General_Concept
is	O
the	O
act	O
of	O
applying	O
database	B-General_Concept
refactorings	I-General_Concept
to	O
evolve	O
an	O
existing	O
database	B-Application
schema	I-Application
(	O
database	B-General_Concept
refactoring	I-General_Concept
is	O
a	O
core	O
practice	O
of	O
evolutionary	O
database	O
design	O
)	O
.	O
</s>
