<s>
PostGIS	B-Application
(	O
)	O
is	O
an	O
open	O
source	O
software	O
program	O
that	O
adds	O
support	O
for	O
geographic	O
objects	O
to	O
the	O
PostgreSQL	B-Application
object-relational	O
database	O
.	O
</s>
<s>
PostGIS	B-Application
follows	O
the	O
Simple	O
Features	O
for	O
SQL	O
specification	O
from	O
the	O
Open	O
Geospatial	O
Consortium	O
(	O
OGC	O
)	O
.	O
</s>
<s>
Technically	O
PostGIS	B-Application
was	O
implemented	O
as	O
a	O
PostgreSQL	B-Application
external	O
extension	O
.	O
</s>
<s>
Since	O
PostGIS	B-Application
3	O
,	O
is	O
a	O
separate	O
PostgreSQL	B-Application
extension	O
called	O
postgis_raster	O
.	O
</s>
<s>
SQL/MM	O
Topology	O
support	O
-	O
via	O
PostgreSQL	B-Application
extension	O
postgis_topology	O
.	O
</s>
<s>
Spatial	O
predicates	O
for	O
determining	O
the	O
interactions	O
of	O
geometries	O
using	O
the	O
3x3	O
DE-9IM	B-Algorithm
(	O
provided	O
by	O
the	O
GEOS	O
software	O
library	O
)	O
.	O
</s>
<s>
R-tree-over-GiST	O
(	O
Generalized	O
Search	O
Tree	O
)	O
spatial	O
indexes	O
for	O
high	O
speed	O
spatial	O
querying	O
.	O
</s>
<s>
Index	O
selectivity	O
support	O
,	O
to	O
provide	O
high	O
performance	O
query	B-Language
plans	I-Language
for	O
mixed	O
spatial/non	O
-spatial	O
queries	O
.	O
</s>
<s>
The	O
PostGIS	B-Application
implementation	O
is	O
based	O
on	O
"	O
light-weight	O
"	O
geometries	O
and	O
indexes	O
optimized	O
to	O
reduce	O
disk	O
and	O
memory	O
footprint	O
.	O
</s>
<s>
PostGIS	B-Application
is	O
registered	O
as	O
"	O
implements	O
the	O
specified	O
standard	O
"	O
for	O
"	O
Simple	O
Features	O
for	O
SQL	O
"	O
by	O
the	O
OGC	O
.	O
</s>
<s>
PostGIS	B-Application
has	O
not	O
been	O
certified	O
as	O
compliant	O
by	O
the	O
OGC	O
.	O
</s>
<s>
Refractions	O
Research	O
released	O
the	O
first	O
version	O
of	O
PostGIS	B-Application
in	O
2001	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
<s>
In	O
2006	O
the	O
OGC	O
registered	O
PostGIS	B-Application
as	O
"implement[ing]	O
the	O
specified	O
standard	O
"	O
for	O
"	O
Simple	O
Features	O
for	O
SQL	O
"	O
.	O
</s>
<s>
Many	O
software	O
products	O
can	O
use	O
PostGIS	B-Application
as	O
a	O
database	O
backend	O
,	O
including	O
:	O
</s>
