<s>
Polyhedra	O
is	O
a	O
family	O
of	O
relational	B-Application
database	I-Application
management	I-Application
systems	I-Application
offered	O
by	O
ENEA	B-Operating_System
AB	I-Operating_System
,	O
a	O
Swedish	O
company	O
.	O
</s>
<s>
The	O
original	O
version	O
of	O
Polyhedra	O
(	O
now	O
referred	O
to	O
as	O
Polyhedra	O
IMDB	O
)	O
was	O
an	O
in-memory	B-General_Concept
database	I-General_Concept
management	I-General_Concept
system	I-General_Concept
which	O
could	O
be	O
used	O
in	O
high	O
availability	O
configurations	O
;	O
in	O
2006	O
Polyhedra	O
Flash	B-Device
DBMS	O
was	O
introduced	O
to	O
allow	O
databases	O
to	O
be	O
stored	O
in	O
flash	B-Device
memory	I-Device
.	O
</s>
<s>
All	O
versions	O
employ	O
the	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
model	I-Operating_System
to	O
ensure	O
the	O
data	O
are	O
protected	O
from	O
misbehaving	O
application	O
software	O
,	O
and	O
they	O
use	O
the	O
same	O
SQL	B-Language
,	O
ODBC	B-Application
and	O
type-4	O
JDBC	B-Language
interfaces	O
.	O
</s>
<s>
Polyhedra	O
is	O
targeted	O
primarily	O
for	O
embedded	B-Architecture
use	O
by	O
Original	O
Equipment	O
Manufacturers	O
(	O
OEMs	O
)	O
,	O
and	O
big-name	O
customers	O
include	O
Ericsson	O
,	O
ABB	O
,	O
Emerson	O
,	O
Lockheed	O
Martin	O
,	O
United	O
Utilities	O
and	O
Siemens	O
AG	O
.	O
</s>
<s>
Polyhedra	O
plc	O
was	O
in	O
turn	O
acquired	O
by	O
Enea	B-Operating_System
AB	I-Operating_System
in	O
2001	O
.	O
</s>
<s>
Building	O
on	O
these	O
experiences	O
,	O
Polyhedra	O
was	O
originally	O
developed	O
"	O
to	O
bring	O
the	O
benefits	O
of	O
relational	O
technology	O
to	O
the	O
embedded	B-Architecture
market	O
"	O
.	O
</s>
<s>
To	O
this	O
end	O
,	O
it	O
had	O
to	O
be	O
small	O
footprint	O
,	O
very	O
fast	O
...	O
and	O
it	O
had	O
to	O
avoid	O
the	O
need	O
for	O
polling	B-General_Concept
,	O
which	O
is	O
a	O
performance	O
killer	O
.	O
</s>
<s>
keep	O
the	O
working	O
copy	O
of	O
the	O
data	O
in-memory	B-General_Concept
(	O
though	O
there	O
is	O
now	O
a	O
variant	O
that	O
keeps	O
the	O
data	O
in	O
a	O
flash-based	B-Application
file	O
)	O
;	O
</s>
<s>
use	O
a	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
architecture	I-Operating_System
to	O
protect	O
the	O
data	O
from	O
corruption	O
by	O
rogue	O
application	O
code	O
;	O
</s>
<s>
have	O
an	O
'	O
active	O
query	B-Language
 '	O
mechanism	O
to	O
update	O
client	O
applications	O
when	O
relevant	O
database	O
changes	O
occur	O
;	O
</s>
<s>
have	O
a	O
very	O
simple	O
processing	O
model	O
where	O
a	O
transaction	B-General_Concept
is	O
either	O
a	O
schema	O
change	O
,	O
a	O
query	B-Language
,	O
or	O
a	O
request	O
for	O
a	O
set	O
of	O
inserts	O
,	O
updates	O
and/or	O
deletes	O
-	O
such	O
alterations	O
can	O
either	O
be	O
expressed	O
via	O
SQL	B-Language
statements	O
or	O
by	O
updating	O
through	O
the	O
active	O
queries	B-Language
with	O
(	O
in	O
conjunction	O
with	O
active	O
queries	B-Language
)	O
an	O
optimistic	B-Operating_System
concurrency	I-Operating_System
mechanism	I-Operating_System
to	O
handle	O
clashing	O
updates	O
;	O
</s>
<s>
have	O
a	O
table	O
inheritance	B-Language
mechanism	O
which	O
,	O
when	O
combined	O
with	O
Database	B-Language
triggers	I-Language
(	O
via	O
the	O
CL	O
language	O
,	O
see	O
below	O
)	O
,	O
allows	O
the	O
database	O
designer	O
to	O
program	O
the	O
database	O
in	O
an	O
object-oriented	O
fashion	O
.	O
</s>
<s>
Table	O
inheritance	B-Language
also	O
avoids	O
or	O
reduces	O
the	O
need	O
for	O
supplementary	O
tables	O
whose	O
primary	O
key	O
is	O
a	O
foreign	O
key	O
to	O
another	O
table	O
,	O
and	O
thus	O
can	O
simplify	O
many	O
queries	B-Language
and	O
updates	O
.	O
</s>
<s>
have	O
a	O
Historian	B-General_Concept
module	O
to	O
allow	O
large	O
volumes	O
of	O
times-series	O
data	O
to	O
be	O
captured	O
,	O
stored	O
,	O
archived	O
and	O
queried	O
in	O
an	O
efficient	O
fashion	O
.	O
</s>
<s>
Polyhedra	O
IMDB	O
achieves	O
data	O
persistence	O
through	O
the	O
use	O
of	O
snapshots	O
and	O
journal	B-General_Concept
logging	I-General_Concept
;	O
Polyhedra	O
Flash	B-Device
DBMS	O
uses	O
shadow	B-Application
paging	I-Application
,	O
with	O
2	O
levels	O
of	O
recursion	O
.	O
</s>
<s>
In	O
addition	O
,	O
Polyhedra	O
can	O
be	O
used	O
in	O
hot-standby	B-General_Concept
configurations	O
for	O
improved	O
availability	O
.	O
</s>
<s>
The	O
transactional	O
model	O
used	O
by	O
all	O
Polyhedra	O
products	O
ensures	O
atomicity	O
,	O
consistency	O
and	O
isolation	O
(	O
as	O
defined	O
by	O
the	O
ACID	O
properties	O
)	O
;	O
durability	O
is	O
enforced	O
in	O
Polyhedra	O
Flash	B-Device
DBMS	O
,	O
while	O
in	O
Polyhedra	O
IMDB	O
clients	O
can	O
choose	O
the	O
durability	O
model	O
when	O
they	O
issue	O
their	O
transactions	O
.	O
</s>
<s>
"	O
The	O
Polyhedra	B-Application
DBMS	I-Application
system	O
is	O
fundamentally	O
different	O
compared	O
to	O
other	O
relational	O
systems	O
,	O
because	O
of	O
its	O
active	O
behaviour	O
.	O
</s>
<s>
This	O
is	O
achieved	O
through	O
two	O
mechanisms	O
,	O
active	O
queries	B-Language
and	O
by	O
the	O
control	O
language	O
(	O
CL	O
)	O
.	O
</s>
<s>
An	O
active	O
query	B-Language
looks	O
quite	O
like	O
a	O
normal	O
query	B-Language
where	O
some	O
data	O
is	O
retrieved	O
and/or	O
written	O
,	O
but	O
instead	O
the	O
query	B-Language
stays	O
in	O
the	O
database	O
until	O
explicitly	O
aborted	O
.	O
</s>
<s>
When	O
a	O
change	O
in	O
the	O
data	O
occurs	O
that	O
would	O
alter	O
the	O
result	O
of	O
the	O
query	B-Language
,	O
the	O
application	O
is	O
notified	O
.	O
</s>
<s>
The	O
CL	O
,	O
which	O
is	O
a	O
fully	O
object-oriented	O
script	O
language	O
that	O
supports	O
encapsulation	O
,	O
information	O
hiding	O
and	O
inheritance	B-Language
,	O
can	O
determine	O
the	O
behaviour	O
of	O
data	O
in	O
the	O
database	O
.	O
</s>
<s>
Polyhedra	O
is	O
not	O
a	O
general-purpose	O
DBMS	O
,	O
as	O
the	O
restricted	O
transactional	O
model	O
does	O
not	O
meet	O
all	O
needs	O
,	O
and	O
its	O
fault-tolerance	O
model	O
is	O
based	O
on	O
the	O
hot-standby	B-General_Concept
approach	O
(	O
to	O
minimise	O
hardware	O
costs	O
)	O
rather	O
than	O
clustering	B-Architecture
(	O
which	O
is	O
better	O
for	O
load-sharing	O
)	O
.	O
</s>
<s>
However	O
,	O
its	O
limitations	O
are	O
benefits	O
in	O
embedded	B-Architecture
use	O
,	O
where	O
the	O
emphasis	O
in	O
a	O
deployed	O
application	O
is	O
on	O
performance	O
and	O
cost	O
rather	O
than	O
handling	O
continually	O
varying	O
usage	O
patterns	O
.	O
</s>
<s>
Most	O
of	O
the	O
Polyhedra	O
products	O
are	O
made	O
available	O
for	O
purchase	O
under	O
a	O
proprietary	B-Application
license	I-Application
,	O
but	O
in	O
2012	O
Enea	O
released	O
Polyhedra	O
Lite	O
under	O
a	O
freeware	B-License
license	O
.	O
</s>
<s>
1993	O
Polyhedra	O
1.0	O
:	O
first	O
commercial	O
release	O
of	O
an	O
in-memory	B-General_Concept
Relational	O
DBMS	O
(	O
RDBMS	B-Application
)	O
.	O
</s>
<s>
1995	O
Ported	O
to	O
Windows	B-Application
and	O
Linux	B-Application
.	O
</s>
<s>
1996	O
Polyhedra	O
2.0	O
:	O
added	O
hot	B-General_Concept
standby	I-General_Concept
configurations	O
for	O
use	O
in	O
applications	O
needing	O
high	O
availability	O
.	O
</s>
<s>
1997	O
Polyhedra	O
3.0	O
:	O
new	O
in-memory	B-General_Concept
data	O
storage	O
engine	O
,	O
for	O
improved	O
space	O
and	O
time	O
efficiency	O
.	O
</s>
<s>
1999	O
Polyhedra	O
3.1	O
:	O
adds	O
new	O
data	O
types	O
,	O
ODBC	B-Application
API	B-General_Concept
.	O
</s>
<s>
2001	O
Polyhedra	O
4.0	O
:	O
JDBC	B-Language
support	O
,	O
additional	O
index	O
type	O
,	O
read-only	O
replicas	O
,	O
multi-threading	O
.	O
</s>
<s>
2002	O
Polyhedra	O
4.1	O
:	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
comms	O
overhauled	O
for	O
substantial	O
performance	O
improvements	O
,	O
especially	O
for	O
client	O
apps	O
using	O
the	O
ODBC	B-Application
API	B-General_Concept
(	O
now	O
deemed	O
the	O
'	O
native	O
 '	O
API	B-General_Concept
for	O
all	O
platforms	O
)	O
.	O
</s>
<s>
2003	O
Polyhedra	O
5.0	O
:	O
UNICODE	O
,	O
schema	O
migration	O
(	O
SQL	B-Language
'	O
ALTER	O
TABLE	O
 '	O
)	O
.	O
</s>
<s>
2004	O
Polyhedra	O
6.0	O
:	O
64-bit	O
support	O
re-introduced	O
,	O
for	O
Linux	B-Application
and	O
Solaris	B-Application
.	O
</s>
<s>
(	O
It	O
previously	O
had	O
been	O
available	O
on	O
DEC	B-Device
Alpha	I-Device
under	O
Digital	B-Operating_System
UNIX	I-Operating_System
until	O
usage	O
of	O
that	O
platform	O
generally	O
died	O
out	O
.	O
)	O
</s>
<s>
Polyhedra64	O
has	O
subsequently	O
been	O
ported	O
to	O
Windows	B-Application
x64	O
.	O
</s>
<s>
2006	O
Polyhedra	O
Flash	B-Device
DBMS	O
introduced	O
,	O
based	O
on	O
a	O
fork	O
of	O
the	O
Polyhedra	O
IMDB	O
code	O
base	O
.	O
</s>
<s>
2007	O
Polyhedra	O
7.0	O
:	O
Polyhedra	O
IMDB	O
and	O
Polyhedra	O
Flash	B-Device
DBMS	O
code	O
bases	O
unified	O
,	O
for	O
ease	O
of	O
support	O
and	O
greater	O
commonality	O
of	O
features	O
.	O
</s>
<s>
2008	O
Polyhedra	O
8.0	O
:	O
Polyhedra	O
Flash	B-Device
DBMS	O
now	O
supports	O
hot	B-General_Concept
standby	I-General_Concept
configurations	O
for	O
use	O
in	O
applications	O
needing	O
high	O
availability	O
,	O
in	O
a	O
similar	O
way	O
to	O
Polyhedra	O
IMDB	O
.	O
</s>
<s>
Polyhedra	O
8.1	O
added	O
Linux/MIPS	O
support	O
,	O
the	O
ability	O
to	O
monitor	O
active	O
queries	B-Language
,	O
and	O
enhancements	O
to	O
the	O
historian	B-General_Concept
.	O
</s>
<s>
Polyhedra	O
8.3	O
:	O
Some	O
SQL	B-Language
enhancements	O
and	O
streaming	O
output	O
from	O
historian	B-General_Concept
.	O
</s>
<s>
2011	O
Polyhedra	O
8.5	O
:	O
better	O
integration	O
with	O
3rd-party	O
tools	O
,	O
and	O
improved	O
performance	O
on	O
Windows	B-Application
.	O
</s>
<s>
Polyhedra	O
Lite	O
introduced	O
:	O
a	O
free-to-use	O
,	O
reduced-functionality	O
version	O
of	O
Polyhedra32	O
IMDB	O
,	O
available	O
for	O
Windows	B-Application
,	O
and	O
for	O
Linux	B-Application
on	O
x86	O
and	O
the	O
Raspberry	B-Operating_System
Pi	I-Operating_System
.	O
</s>
<s>
Polyhedra	O
8.7	O
:	O
locking	O
and	O
cascaded	B-Application
deletes	I-Application
.	O
</s>
<s>
2014	O
Polyhedra	O
8.9	O
:	O
SQL	B-Language
enhancements	O
(	O
GROUP	O
BY	O
and	O
HAVING	O
,	O
DISTINCT	O
,	O
outer	B-Language
joins	I-Language
)	O
,	O
security	O
enhancements	O
,	O
and	O
online	O
backups	O
for	O
time-series	O
data	O
.	O
</s>
<s>
2015	O
Polyhedra	O
9.0	O
:	O
read-only	O
partial	O
database	O
replication	O
via	O
a	O
subscription	O
mechanism	O
,	O
an	O
ADO.NET	B-Device
data	I-Device
provider	I-Device
for	O
Polyhedra	O
,	O
and	O
enhancements	O
to	O
the	O
proprietary	B-Application
'	O
callback	O
API	B-General_Concept
 '	O
that	O
can	O
yield	O
significant	O
performance	O
enhancements	O
.	O
</s>
<s>
2016	O
Polyhedra	O
9.1	O
:	O
bi-directional	O
subscription	O
and	O
partial	O
table	O
replication	O
,	O
internal	O
resource	O
monitoring	O
,	O
and	O
a	O
Python	B-Language
DB-API	O
module	O
with	O
extensions	O
for	O
Polyhedra-specific	O
features	O
such	O
as	O
active	O
queries	B-Language
.	O
</s>
<s>
Polyhedra	O
9.2	O
:	O
reduced	O
memory	O
usage	O
,	O
RDI	O
(	O
Remove	O
Device	O
Interface	O
)	O
API	B-General_Concept
,	O
OPC	O
UA	O
RDI	O
,	O
and	O
SQL	B-Language
EXPLAIN	O
command	O
.	O
</s>
<s>
2018	O
Polyhedra	O
9.4	O
:	O
Embedded	B-Architecture
database	O
API	B-General_Concept
and	O
limited	O
SQL	B-Language
function-based	O
indexes	O
.	O
</s>
<s>
2020	O
Polyhedra	O
9.6	O
:	O
REST	O
API	B-General_Concept
,	O
WebSocket	O
Server	O
and	O
IMDB	O
API	B-General_Concept
Enhancements	O
.	O
</s>
<s>
2021	O
Polyhedra	O
9.7	O
:	O
IMDB	O
API	B-General_Concept
BLOB	O
caching	O
,	O
multiple	O
database	O
support	O
.	O
</s>
