<s>
Sessions	O
are	O
also	O
used	O
in	O
operational	B-Architecture
analytics	I-Architecture
and	O
provision	O
of	O
user-specific	B-Application
recommendations	I-Application
.	O
</s>
<s>
There	O
are	O
two	O
primary	O
methods	O
used	O
to	O
define	O
a	O
session	O
:	O
time-oriented	O
approaches	O
based	O
on	O
continuity	O
in	O
user	O
activity	O
and	O
navigation-based	O
approaches	O
based	O
on	O
continuity	O
in	O
a	O
chain	O
of	O
requested	B-Protocol
pages	O
.	O
</s>
<s>
The	O
definition	O
of	O
"	O
session	O
"	O
varies	O
,	O
particularly	O
when	O
applied	O
to	O
search	B-Application
engines	I-Application
.	O
</s>
<s>
In	O
the	O
context	O
of	O
search	B-Application
engines	I-Application
,	O
"	O
sessions	O
"	O
and	O
"	O
query	O
sessions	O
"	O
have	O
at	O
least	O
two	O
definitions	O
.	O
</s>
<s>
Sessions	O
are	O
also	O
used	O
for	O
operational	B-Architecture
analytics	I-Architecture
,	O
data	O
anonymization	O
,	O
identifying	O
networking	O
anomalies	O
,	O
and	O
synthetic	O
workload	O
generation	O
for	O
testing	O
servers	O
with	O
artificial	O
traffic	O
.	O
</s>
<s>
This	O
is	O
known	O
as	O
"	O
session	B-Protocol
reconstruction	I-Protocol
"	O
.	O
</s>
<s>
Approaches	O
to	O
session	B-Protocol
reconstruction	I-Protocol
can	O
be	O
divided	O
into	O
two	O
main	O
categories	O
:	O
time-oriented	O
,	O
and	O
navigation-oriented	O
.	O
</s>
<s>
Time-oriented	O
approaches	O
to	O
session	B-Protocol
reconstruction	I-Protocol
look	O
for	O
a	O
set	O
period	O
of	O
user	O
inactivity	O
commonly	O
called	O
an	O
"	O
inactivity	O
threshold.	O
"	O
</s>
<s>
A	O
simpler	O
approach	O
,	O
which	O
does	O
not	O
take	O
backtracking	O
into	O
account	O
,	O
is	O
to	O
simply	O
require	O
that	O
the	O
HTTP	B-Protocol
referer	I-Protocol
of	O
each	O
request	O
be	O
a	O
page	O
that	O
is	O
already	O
in	O
the	O
session	O
.	O
</s>
<s>
This	O
class	O
of	O
heuristics	O
"	O
exhibits	O
very	O
poor	O
performance	O
"	O
on	O
websites	O
that	O
contain	O
framesets	B-General_Concept
.	O
</s>
