<s>
Sensor	B-Algorithm
web	I-Algorithm
is	O
a	O
type	O
of	O
sensor	B-Architecture
network	I-Architecture
that	O
heavily	O
utilizes	O
the	O
World	O
Wide	O
Web	O
and	O
is	O
especially	O
suited	O
for	O
environmental	O
monitoring	O
.	O
</s>
<s>
OGC	O
's	O
Sensor	B-Algorithm
Web	I-Algorithm
Enablement	O
(	O
SWE	O
)	O
framework	O
defines	O
a	O
suite	O
of	O
web	O
service	O
interfaces	O
and	O
communication	O
protocols	O
abstracting	O
from	O
the	O
heterogeneity	O
of	O
sensor	O
(	O
network	O
)	O
communication	O
.	O
</s>
<s>
The	O
term	O
"	O
sensor	B-Algorithm
web	I-Algorithm
"	O
was	O
first	O
used	O
by	O
Kevin	O
Delin	O
of	O
NASA	O
in	O
1997	O
,	O
</s>
<s>
to	O
describe	O
a	O
novel	O
wireless	B-Architecture
sensor	I-Architecture
network	I-Architecture
architecture	O
where	O
the	O
individual	O
pieces	O
could	O
act	O
and	O
coordinate	O
as	O
a	O
whole	O
.	O
</s>
<s>
In	O
this	O
sense	O
,	O
the	O
term	O
describes	O
a	O
specific	O
type	O
of	O
sensor	B-Architecture
network	I-Architecture
:	O
an	O
amorphous	O
network	O
of	O
spatially	O
distributed	O
sensor	O
platforms	O
(	O
pods	O
)	O
that	O
wirelessly	O
communicate	O
with	O
each	O
other	O
.	O
</s>
<s>
This	O
amorphous	O
architecture	O
is	O
unique	O
since	O
it	O
is	O
both	O
synchronous	O
and	O
router-free	O
,	O
making	O
it	O
distinct	O
from	O
the	O
more	O
typical	O
TCP/IP	B-Protocol
-like	O
network	O
schemes	O
.	O
</s>
<s>
Hence	O
,	O
the	O
architecture	O
allows	O
every	O
pod	O
to	O
know	O
what	O
is	O
going	O
on	O
with	O
every	O
other	O
pod	O
throughout	O
the	O
sensor	B-Algorithm
web	I-Algorithm
at	O
each	O
measurement	O
cycle	O
.	O
</s>
<s>
Delin	O
's	O
definition	O
of	O
a	O
sensor	B-Algorithm
web	I-Algorithm
was	O
an	O
autonomous	O
,	O
stand-alone	O
,	O
sensing	O
entity	O
–	O
capable	O
of	O
interpreting	O
and	O
reacting	O
to	O
the	O
data	O
measured	O
–	O
that	O
does	O
not	O
necessarily	O
require	O
the	O
presence	O
of	O
the	O
World	O
Wide	O
Web	O
to	O
function	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
on-the-fly	O
data	O
fusion	O
,	O
such	O
as	O
false-positive	O
identification	O
and	O
plume	O
tracking	O
,	O
can	O
occur	O
within	O
the	O
sensor	B-Algorithm
web	I-Algorithm
itself	O
and	O
the	O
system	O
subsequently	O
reacts	O
as	O
a	O
coordinated	O
,	O
collective	O
whole	O
to	O
the	O
incoming	O
data	O
stream	O
.	O
</s>
<s>
For	O
example	O
,	O
instead	O
of	O
having	O
uncoordinated	O
smoke	O
detectors	O
,	O
a	O
sensor	B-Algorithm
web	I-Algorithm
can	O
react	O
as	O
a	O
single	O
,	O
spatially	O
dispersed	O
,	O
fire	O
locator	O
.	O
</s>
<s>
The	O
term	O
"	O
sensor	B-Algorithm
web	I-Algorithm
"	O
has	O
also	O
morphed	O
into	O
sometimes	O
being	O
associated	O
with	O
an	O
additional	O
layer	O
connecting	O
sensors	O
to	O
the	O
World	O
Wide	O
Web	O
.	O
</s>
<s>
The	O
Sensor	B-Algorithm
Web	I-Algorithm
Enablement	O
(	O
SWE	O
)	O
initiative	O
of	O
the	O
Open	O
Geospatial	O
Consortium	O
(	O
OGC	O
)	O
defines	O
service	O
interfaces	O
which	O
enable	O
an	O
interoperable	O
usage	O
of	O
sensor	O
resources	O
by	O
enabling	O
their	O
discovery	O
,	O
access	O
,	O
tasking	O
,	O
as	O
well	O
as	O
eventing	O
and	O
alerting	O
.	O
</s>
<s>
By	O
defining	O
standardized	O
service	O
interfaces	O
,	O
a	O
sensor	B-Algorithm
web	I-Algorithm
based	O
on	O
SWE	O
services	O
hides	O
the	O
heterogeneity	O
of	O
an	O
underlying	O
sensor	B-Architecture
network	I-Architecture
,	O
its	O
communication	O
details	O
and	O
various	O
hardware	O
components	O
,	O
from	O
the	O
applications	O
built	O
on	O
top	O
of	O
it	O
.	O
</s>
<s>
OGC	O
's	O
SWE	O
initiative	O
defines	O
the	O
term	O
"	O
sensor	B-Algorithm
web	I-Algorithm
"	O
as	O
an	O
infrastructure	O
enabling	O
access	O
to	O
sensor	B-Architecture
networks	I-Architecture
and	O
archived	O
sensor	O
data	O
that	O
can	O
be	O
discovered	O
and	O
accessed	O
using	O
standard	O
protocols	O
and	O
application	O
programming	O
interfaces	O
.	O
</s>
<s>
Delin	O
designed	O
a	O
sensor	B-Algorithm
web	I-Algorithm
as	O
a	O
web	O
of	O
interconnected	O
pods	O
.	O
</s>
<s>
All	O
pods	O
in	O
a	O
sensor	B-Algorithm
web	I-Algorithm
are	O
equivalent	O
in	O
hardware	O
(	O
there	O
are	O
no	O
special	O
"	O
gateway	O
"	O
or	O
"	O
slave	O
"	O
pods	O
)	O
.	O
</s>
<s>
Nevertheless	O
,	O
there	O
are	O
additional	O
functions	O
that	O
pods	O
can	O
perform	O
besides	O
participating	O
in	O
the	O
general	O
sensor	B-Algorithm
web	I-Algorithm
function	O
.	O
</s>
<s>
Any	O
pod	O
of	O
a	O
sensor	B-Algorithm
web	I-Algorithm
can	O
be	O
a	O
portal	O
pod	O
and	O
provides	O
users	O
access	O
to	O
the	O
sensor	B-Algorithm
web	I-Algorithm
(	O
both	O
input	O
and	O
output	O
)	O
.	O
</s>
<s>
The	O
term	O
of	O
mother	O
pod	O
refers	O
to	O
the	O
pod	O
that	O
contains	O
the	O
master	O
clock	O
of	O
the	O
synchronous	O
sensor	B-Algorithm
web	I-Algorithm
system	O
.	O
</s>
<s>
Because	O
of	O
the	O
inherent	O
hopping	O
of	O
data	O
within	O
a	O
sensor	B-Algorithm
web	I-Algorithm
,	O
a	O
pod	O
with	O
no	O
attached	O
sensors	O
can	O
be	O
deployed	O
as	O
a	O
relay	O
with	O
the	O
single	O
purpose	O
of	O
facilitating	O
communication	O
between	O
the	O
other	O
pods	O
and	O
to	O
expand	O
the	O
communication	O
range	O
to	O
a	O
particular	O
end-point	O
(	O
such	O
as	O
a	O
mother	O
pod	O
)	O
.	O
</s>
<s>
a	O
processing	O
unit	O
such	O
as	O
a	O
micro-controller	B-Architecture
or	O
microprocessor	B-Architecture
,	O
</s>
<s>
The	O
number	O
of	O
pods	O
may	O
vary	O
,	O
with	O
examples	O
of	O
sensor	B-Algorithm
webs	I-Algorithm
with	O
12	O
to	O
30	O
pods	O
.	O
</s>
<s>
Sensor	B-Algorithm
web	I-Algorithm
measurement	O
cycles	O
have	O
typically	O
been	O
between	O
30	O
seconds	O
and	O
15	O
minutes	O
for	O
deployed	O
systems	O
thus	O
far	O
.	O
</s>
<s>
Sensor	B-Algorithm
webs	I-Algorithm
consisting	O
of	O
pods	O
have	O
been	O
deployed	O
that	O
have	O
spanned	O
miles	O
and	O
run	O
continuously	O
for	O
years	O
.	O
</s>
