<s>
Metakit	B-Language
is	O
an	O
embedded	B-Application
database	I-Application
library	O
with	O
a	O
small	O
footprint	O
.	O
</s>
<s>
It	O
fills	O
the	O
gap	O
between	O
flat-file	B-Application
,	O
relational	B-Architecture
,	O
object-oriented	B-Application
,	O
and	O
tree-structured	B-General_Concept
databases	O
,	O
supporting	O
relational	B-Architecture
joins	B-Language
,	O
serialization	O
,	O
nested	O
structures	O
,	O
and	O
instant	O
schema	O
evolution	O
.	O
</s>
<s>
Interfaces	O
for	O
C++	B-Language
(	O
native	O
)	O
,	O
Python	B-Language
and	O
Tcl	B-Operating_System
are	O
the	O
most	O
used	O
.	O
</s>
<s>
Metakit	B-Language
was	O
written	O
by	O
Jean-Claude	O
Wippler	O
,	O
a	O
software	O
developer	O
from	O
the	O
Netherlands	O
.	O
</s>
<s>
Its	O
development	O
started	O
around	O
1997	O
and	O
in	O
2001	O
it	O
released	O
as	O
open	O
source	O
under	O
the	O
MIT	B-License
X11	I-License
license	I-License
.	O
</s>
<s>
In	O
the	O
last	O
few	O
years	O
,	O
however	O
,	O
Wippler	O
has	O
spent	O
less	O
time	O
on	O
Metakit	B-Language
and	O
more	O
on	O
his	O
other	O
projects	O
.	O
</s>
<s>
The	O
database	O
is	O
used	O
in	O
several	O
commercial	O
products	O
(	O
including	O
Address	B-Operating_System
Book	I-Operating_System
in	O
Mac	O
OS	O
X	O
10.4	O
and	O
earlier	O
)	O
and	O
in	O
several	O
open	O
source	O
(	O
for	O
example	O
KDE	B-Application
's	I-Application
feed	O
reader	O
Akregator	O
)	O
and	O
in-house	O
projects	O
(	O
typically	O
using	O
Python	B-Language
or	O
TCL	B-Operating_System
interface	O
)	O
.	O
</s>
<s>
A	O
related	O
project	O
,	O
Starkit	O
(	O
virtual	B-Application
file	I-Application
system	I-Application
for	O
TCL	B-Operating_System
)	O
,	O
written	O
by	O
Wippler	O
,	O
reached	O
popularity	O
among	O
TCL	B-Operating_System
programmers	O
.	O
</s>
<s>
The	O
mailing-list	O
of	O
Metakit	B-Language
has	O
active	O
subscribers	O
and	O
is	O
regularly	O
posted	O
to	O
by	O
Wippler	O
.	O
</s>
<s>
Unlike	O
most	O
other	O
database	O
systems	O
which	O
store	O
rows	O
of	O
a	O
database	B-Application
table	I-Application
in	O
one	O
place	O
(	O
row-oriented	O
architecture	O
)	O
Metakit	B-Language
stores	O
individual	O
columns	O
separately	O
(	O
column-oriented	B-General_Concept
architecture	I-General_Concept
)	O
.	O
</s>
<s>
For	O
many	O
years	O
only	O
linear	O
access	O
to	O
the	O
tables	O
was	O
possible	O
(	O
with	O
complexity	O
O(1 )	O
for	O
access	O
and	O
O(N )	O
for	O
search	O
)	O
,	O
later	O
hash	B-Algorithm
structures	I-Algorithm
and	O
B-tree	B-Architecture
like	O
structures	O
were	O
added	O
(	O
reducing	O
typical	O
search	O
complexity	O
to	O
O(1 )	O
)	O
.	O
</s>
<s>
Relational	B-Architecture
operations	O
(	O
like	O
group-by	O
and	O
joins	B-Language
)	O
were	O
also	O
added	O
over	O
years	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
combine	O
and	O
process	O
table	B-Application
data	O
via	O
flexible	O
mechanisms	O
called	O
views	O
.	O
</s>
<s>
Disk	O
space	O
overhead	O
of	O
Metakit	B-Language
is	O
very	O
low	O
—	O
several	O
techniques	O
are	O
employed	O
automatically	O
to	O
reduce	O
it	O
as	O
much	O
as	O
possible	O
.	O
</s>
<s>
Viewer	O
of	O
Metakit	B-Language
database	O
structures	O
(	O
named	O
Kitview	O
)	O
is	O
provided	O
.	O
</s>
<s>
Practical	O
limit	O
to	O
database	O
size	O
is	O
around	O
1GB	O
(	O
even	O
on	O
64-bit	B-Device
platforms	O
)	O
.	O
</s>
<s>
Multithreaded	O
and	O
multiuser	O
access	O
requires	O
manual	O
support	O
from	O
the	O
programmer	O
and	O
is	O
discouraged	O
(	O
in	O
C++	B-Language
,	O
TCL	B-Operating_System
and	O
Python	B-Language
use	O
one	O
automatically	O
global	O
lock	O
)	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
obtain	O
somewhat	O
better	O
performance	O
than	O
with	O
other	O
databases	O
(	O
published	O
benchmarks	O
include	O
SQLite	B-Language
and	O
Berkeley	B-Language
DB	I-Language
)	O
but	O
it	O
requires	O
lot	O
of	O
testing	O
and	O
lot	O
of	O
knowledge	O
of	O
Metakit	B-Language
internals	O
.	O
</s>
<s>
Metakit	B-Language
's	O
API	B-Application
is	O
low	O
level	O
,	O
compared	O
to	O
SQL	B-Language
.	O
</s>
<s>
The	O
biggest	O
weakness	O
of	O
Metakit	B-Language
is	O
its	O
rather	O
spotty	O
and	O
sometimes	O
obsolete	O
documentation	O
.	O
</s>
<s>
Full	O
understanding	O
of	O
its	O
API	B-Application
and	O
performance	O
tuning	O
requires	O
deep	O
study	O
of	O
library	O
's	O
source	O
code	O
.	O
</s>
<s>
Metakits	B-Language
terminology	O
has	O
many	O
differences	O
to	O
standard	O
database	O
terminology	O
.	O
</s>
<s>
The	O
API	B-Application
and	O
file	O
format	O
has	O
changed	O
several	O
times	O
over	O
time	O
.	O
</s>
<s>
Metakit	B-Language
is	O
tested	O
on	O
Windows	B-Application
,	O
Unix	B-Application
and	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
.	O
</s>
<s>
C++	B-Language
(	O
native	O
)	O
:	O
Metakit	B-Language
is	O
written	O
in	O
C++	B-Language
(	O
without	O
using	O
its	O
new	O
features	O
so	O
even	O
very	O
old	O
compilers	O
can	O
handle	O
it	O
)	O
.	O
</s>
<s>
Tcl	B-Operating_System
:	O
called	O
Mk4tcl	O
,	O
with	O
an	O
optional	O
OO	O
binding	O
on	O
top	O
called	O
Oomk	O
.	O
</s>
<s>
Other	O
languages	O
can	O
be	O
interfaced	O
with	O
help	O
of	O
SWIG	B-Application
.	O
</s>
