<s>
For	O
instant	B-Application
messaging	I-Application
,	O
a	O
presence	B-Protocol
information	I-Protocol
watcher	B-Protocol
is	O
an	O
entity	O
that	O
requests	O
presence	B-Protocol
information	I-Protocol
about	O
a	O
presentity	B-Protocol
from	O
a	O
presence	B-Protocol
service	I-Protocol
.	O
</s>
<s>
Usually	O
in	O
order	O
to	O
get	O
presence	B-Protocol
information	I-Protocol
a	O
watcher	B-Protocol
have	O
to	O
subscribe	O
for	O
it	O
to	O
a	O
presence	O
server	O
.	O
</s>
<s>
When	O
subscribed	O
,	O
the	O
watcher	B-Protocol
receives	O
event	O
notifications	O
as	O
presence	B-Protocol
information	I-Protocol
changes	O
.	O
</s>
<s>
Alternatively	O
watcher	B-Protocol
may	O
fetch	O
presence	B-Protocol
information	I-Protocol
without	O
subscribing	O
to	O
it	O
.	O
</s>
