<s>
The	O
Spatiotemporal	B-Application
Epidemiological	I-Application
Modeler	I-Application
(	O
STEM	O
)	O
is	O
free	B-Application
software	I-Application
available	O
through	O
the	B-Application
Eclipse	I-Application
Foundation	I-Application
.	O
</s>
<s>
STEM	O
uses	O
a	O
component	B-Architecture
software	I-Architecture
architecture	I-Architecture
based	O
on	O
the	O
OSGi	B-Application
standard	O
.	O
</s>
<s>
The	O
Eclipse	B-Language
Equinox	I-Language
platform	O
is	O
a	O
reference	O
implementation	O
of	O
that	O
standard	O
.	O
</s>
<s>
By	O
using	O
a	O
component	B-Architecture
software	I-Architecture
architecture	I-Architecture
,	O
all	O
of	O
the	O
components	O
or	O
elements	O
required	O
for	O
a	O
disease	O
model	O
,	O
including	O
the	O
code	O
and	O
the	O
data	O
are	O
available	O
as	O
software	O
building	O
blocks	O
that	O
can	O
be	O
independently	O
exchanged	O
,	O
extended	O
,	O
reused	O
,	O
or	O
replaced	O
.	O
</s>
<s>
These	O
building	O
blocks	O
or	O
plug-ins	B-Application
are	O
called	O
eclipse	O
"	O
plug-ins	B-Application
"	O
or	O
"	O
extensions	O
"	O
.	O
</s>
<s>
STEM	O
plug-ins	B-Application
contain	O
denominator	O
data	O
for	O
administrative	O
regions	O
of	O
interest	O
.	O
</s>
<s>
STEM	O
currently	O
includes	O
a	O
large	O
number	O
of	O
plug-ins	B-Application
for	O
the	O
244	O
countries	O
and	O
dependent	O
areas	O
defined	O
by	O
the	O
Geographic	O
Coding	O
Standard	O
maintained	O
by	O
the	O
International	O
Organization	O
for	O
Standardization	O
.	O
</s>
<s>
These	O
plug-ins	B-Application
contain	O
global	O
data	O
including	O
geographic	B-General_Concept
data	I-General_Concept
,	O
population	O
data	O
,	O
demographics	O
,	O
and	O
basic	O
models	O
of	O
disease	O
.	O
</s>
<s>
Other	O
plug-ins	B-Application
describe	O
relationships	O
between	O
regions	O
including	O
nearest-neighbor	O
or	O
adjacency	O
relationships	O
as	O
well	O
as	O
information	O
about	O
transportation	O
,	O
such	O
as	O
connections	O
by	O
roads	O
and	O
a	O
model	O
of	O
air	O
transportation	O
.	O
</s>
<s>
This	O
graphical	O
representation	O
is	O
implemented	O
using	O
the	O
Eclipse	B-Language
Modeling	I-Language
Framework	I-Language
(	O
EMF	O
)	O
.	O
</s>
<s>
Since	O
a	O
model	O
can	O
be	O
built	O
up	O
using	O
separate	O
subgraphs	O
,	O
STEM	O
enables	O
model	O
composition	B-Language
.	O
</s>
<s>
As	O
an	O
open	B-Application
source	I-Application
project	O
,	O
users	O
are	O
encouraged	O
to	O
create	O
their	O
own	O
plug-ins	B-Application
(	O
both	O
data	O
and	O
models	O
)	O
and	O
,	O
if	O
appropriate	O
,	O
to	O
contribute	O
their	O
work	O
back	O
to	O
the	O
project	O
.	O
</s>
