<s>
Sequential	B-Algorithm
pattern	I-Algorithm
mining	I-Algorithm
is	O
a	O
topic	O
of	O
data	B-Application
mining	I-Application
concerned	O
with	O
finding	O
statistically	O
relevant	O
patterns	O
between	O
data	O
examples	O
where	O
the	O
values	O
are	O
delivered	O
in	O
a	O
sequence	O
.	O
</s>
<s>
Sequential	B-Algorithm
pattern	I-Algorithm
mining	I-Algorithm
is	O
a	O
special	O
case	O
of	O
structured	B-Algorithm
data	I-Algorithm
mining	I-Algorithm
.	O
</s>
<s>
In	O
general	O
,	O
sequence	B-Algorithm
mining	I-Algorithm
problems	O
can	O
be	O
classified	O
as	O
string	O
mining	O
which	O
is	O
typically	O
based	O
on	O
string	O
processing	O
algorithms	O
and	O
itemset	B-Algorithm
mining	I-Algorithm
which	O
is	O
typically	O
based	O
on	O
association	B-Algorithm
rule	I-Algorithm
learning	I-Algorithm
.	O
</s>
<s>
Local	O
process	O
models	O
extend	O
sequential	B-Algorithm
pattern	I-Algorithm
mining	I-Algorithm
to	O
more	O
complex	O
patterns	O
that	O
can	O
include	O
(	O
exclusive	O
)	O
choices	O
,	O
loops	O
,	O
and	O
concurrency	O
constructs	O
in	O
addition	O
to	O
the	O
sequential	O
ordering	O
construct	O
.	O
</s>
<s>
String	O
mining	O
typically	O
deals	O
with	O
a	O
limited	O
alphabet	B-Application
for	O
items	O
that	O
appear	O
in	O
a	O
sequence	O
,	O
but	O
the	O
sequence	O
itself	O
may	O
be	O
typically	O
very	O
long	O
.	O
</s>
<s>
Examples	O
of	O
an	O
alphabet	B-Application
can	O
be	O
those	O
in	O
the	O
ASCII	B-Protocol
character	I-Protocol
set	I-Protocol
used	O
in	O
natural	O
language	O
text	O
,	O
nucleotide	O
bases	O
'	O
A	O
 '	O
,	O
'	O
G	O
 '	O
,	O
'	O
C	O
 '	O
and	O
'	O
T	O
 '	O
in	O
DNA	O
sequences	O
,	O
or	O
amino	O
acids	O
for	O
protein	O
sequences	O
.	O
</s>
<s>
In	O
biology	O
applications	O
analysis	O
of	O
the	O
arrangement	O
of	O
the	O
alphabet	B-Application
in	O
strings	O
can	O
be	O
used	O
to	O
examine	O
gene	O
and	O
protein	O
sequences	O
to	O
determine	O
their	O
properties	O
.	O
</s>
<s>
Repeat-related	O
problems	O
:	O
that	O
deal	O
with	O
operations	O
on	O
single	O
sequences	O
and	O
can	O
be	O
based	O
on	O
exact	B-Algorithm
string	I-Algorithm
matching	I-Algorithm
or	O
approximate	B-Algorithm
string	I-Algorithm
matching	I-Algorithm
methods	O
for	O
finding	O
dispersed	O
fixed	O
length	O
and	O
maximal	O
length	O
repeats	O
,	O
finding	O
tandem	O
repeats	O
,	O
and	O
finding	O
unique	O
subsequences	O
and	O
missing	O
(	O
un-spelled	O
)	O
subsequences	O
.	O
</s>
<s>
Alignment	O
problems	O
:	O
that	O
deal	O
with	O
comparison	O
between	O
strings	O
by	O
first	O
aligning	O
one	O
or	O
more	O
sequences	O
;	O
examples	O
of	O
popular	O
methods	O
include	O
BLAST	B-Application
for	O
comparing	O
a	O
single	O
sequence	O
with	O
multiple	O
sequences	O
in	O
a	O
database	O
,	O
and	O
ClustalW	B-Application
for	O
multiple	O
alignments	O
.	O
</s>
<s>
See	O
sequence	B-Algorithm
alignment	I-Algorithm
.	O
</s>
<s>
Some	O
problems	O
in	O
sequence	B-Algorithm
mining	I-Algorithm
lend	O
themselves	O
to	O
discovering	O
frequent	O
itemsets	O
and	O
the	O
order	O
they	O
appear	O
,	O
for	O
example	O
,	O
one	O
is	O
seeking	O
rules	O
of	O
the	O
form	O
"	O
if	O
a	O
{	O
customer	O
buys	O
a	O
car}	O
,	O
he	O
or	O
she	O
is	O
likely	O
to	O
{	O
buy	O
insurance}	O
within	O
1	O
week	O
"	O
,	O
or	O
in	O
the	O
context	O
of	O
stock	O
prices	O
,	O
"	O
if	O
{	O
Nokia	O
up	O
and	O
Ericsson	O
up}	O
,	O
it	O
is	O
likely	O
that	O
{	O
Motorola	O
up	O
and	O
Samsung	O
up}	O
within	O
2	O
days	O
"	O
.	O
</s>
<s>
Traditionally	O
,	O
itemset	B-Algorithm
mining	I-Algorithm
is	O
used	O
in	O
marketing	O
applications	O
for	O
discovering	O
regularities	O
between	O
frequently	O
co-occurring	O
items	O
in	O
large	O
transactions	O
.	O
</s>
<s>
The	O
two	O
common	O
techniques	O
that	O
are	O
applied	O
to	O
sequence	O
databases	O
for	O
frequent	B-Algorithm
itemset	I-Algorithm
mining	O
are	O
the	O
influential	O
apriori	B-Algorithm
algorithm	I-Algorithm
and	O
the	O
more-recent	O
FP-growth	O
technique	O
.	O
</s>
<s>
To	O
solve	O
this	O
problem	O
,	O
George	O
and	O
Binu	O
(	O
2013	O
)	O
have	O
proposed	O
an	O
approach	O
to	O
mine	O
user	O
buying	O
patterns	O
using	O
PrefixSpan	B-Algorithm
algorithm	O
and	O
place	O
the	O
products	O
on	O
shelves	O
based	O
on	O
the	O
order	O
of	O
mined	O
purchasing	O
patterns	O
.	O
</s>
