<s>
Polyinstantiation	B-Application
in	O
computer	B-General_Concept
science	I-General_Concept
is	O
the	O
concept	O
of	O
type	O
(	O
class	O
,	O
database	O
row	O
or	O
otherwise	O
)	O
being	O
instantiated	O
into	O
multiple	O
independent	O
instances	O
(	O
objects	O
,	O
copies	O
)	O
.	O
</s>
<s>
It	O
may	O
also	O
indicate	O
,	O
such	O
as	O
in	O
the	O
case	O
of	O
database	O
polyinstantiation	B-Application
,	O
that	O
two	O
different	O
instances	O
have	O
the	O
same	O
name	O
(	O
identifier	O
,	O
primary	O
key	O
)	O
.	O
</s>
<s>
In	O
Operating	O
system	O
security	O
,	O
polyinstantiation	B-Application
is	O
the	O
concept	O
of	O
creating	O
a	O
user	O
or	O
process	O
specific	O
view	O
of	O
a	O
shared	O
resource	O
.	O
</s>
<s>
Process	O
A	O
cannot	O
affect	O
process	O
B	O
by	O
writing	O
malicious	O
code	O
to	O
a	O
shared	O
resource	O
,	O
such	O
as	O
UNIX	B-Application
directory	O
/tmp	O
.	O
</s>
<s>
Polyinstantiation	B-Application
of	O
shared	O
resources	O
have	O
similar	O
goals	O
as	O
process	O
isolation	O
,	O
an	O
application	O
of	O
virtual	B-Architecture
memory	I-Architecture
,	O
where	O
processes	O
are	O
assigned	O
their	O
own	O
isolated	O
virtual	B-General_Concept
address	I-General_Concept
space	I-General_Concept
to	O
prevent	O
process	O
A	O
writing	O
into	O
the	O
memory	O
space	O
of	O
process	O
B	O
.	O
</s>
<s>
In	O
databases	O
,	O
polyinstantiation	B-Application
is	O
database-related	O
SQL	B-Language
(	O
structured	B-Language
query	I-Language
language	I-Language
)	O
terminology	O
.	O
</s>
<s>
Although	O
useful	O
from	O
a	O
security	O
standpoint	O
,	O
polyinstantiation	B-Application
raises	O
several	O
problems	O
:	O
</s>
<s>
In	O
cryptography	O
,	O
polyinstantiation	B-Application
is	O
the	O
existence	O
of	O
a	O
cryptographic	O
key	O
in	O
more	O
than	O
one	O
secure	O
physical	O
location	O
.	O
</s>
