<s>
Structure	B-Algorithm
mining	I-Algorithm
or	O
structured	B-Algorithm
data	I-Algorithm
mining	I-Algorithm
is	O
the	O
process	O
of	O
finding	O
and	O
extracting	O
useful	O
information	O
from	O
semi-structured	B-Application
data	I-Application
sets	O
.	O
</s>
<s>
Graph	B-Algorithm
mining	I-Algorithm
,	O
sequential	B-Algorithm
pattern	I-Algorithm
mining	I-Algorithm
and	O
molecule	O
mining	O
are	O
special	O
cases	O
of	O
structured	B-Algorithm
data	I-Algorithm
mining	I-Algorithm
.	O
</s>
<s>
The	O
growth	O
of	O
the	O
use	O
of	O
semi-structured	B-Application
data	I-Application
has	O
created	O
new	O
opportunities	O
for	O
data	B-Application
mining	I-Application
,	O
which	O
has	O
traditionally	O
been	O
concerned	O
with	O
tabular	O
data	O
sets	O
,	O
reflecting	O
the	O
strong	O
association	O
between	O
data	B-Application
mining	I-Application
and	O
relational	B-Application
databases	I-Application
.	O
</s>
<s>
Much	O
of	O
the	O
world	O
's	O
interesting	O
and	O
mineable	O
data	O
does	O
not	O
easily	O
fold	O
into	O
relational	B-Application
databases	I-Application
,	O
though	O
a	O
generation	O
of	O
software	O
engineers	O
have	O
been	O
trained	O
to	O
believe	O
this	O
was	O
the	O
only	O
way	O
to	O
handle	O
data	O
,	O
and	O
data	B-Application
mining	I-Application
algorithms	O
have	O
generally	O
been	O
developed	O
only	O
to	O
cope	O
with	O
tabular	O
data	O
.	O
</s>
<s>
XML	B-Protocol
,	O
being	O
the	O
most	O
frequent	O
way	O
of	O
representing	O
semi-structured	B-Application
data	I-Application
,	O
is	O
able	O
to	O
represent	O
both	O
tabular	O
data	O
and	O
arbitrary	O
trees	O
.	O
</s>
<s>
Any	O
particular	O
representation	O
of	O
data	O
to	O
be	O
exchanged	O
between	O
two	O
applications	O
in	O
XML	B-Protocol
is	O
normally	O
described	O
by	O
a	O
schema	O
often	O
written	O
in	O
XSD	O
.	O
</s>
<s>
Messages	O
and	O
data	O
,	O
therefore	O
,	O
that	O
are	O
transmitted	O
or	O
encoded	O
using	O
XML	B-Protocol
and	O
that	O
conform	O
to	O
the	O
same	O
schema	O
are	O
liable	O
to	O
contain	O
very	O
different	O
data	O
depending	O
on	O
what	O
is	O
being	O
transmitted	O
.	O
</s>
<s>
Such	O
data	O
presents	O
large	O
problems	O
for	O
conventional	O
data	B-Application
mining	I-Application
.	O
</s>
<s>
Building	O
a	O
training	O
set	O
from	O
such	O
data	O
means	O
that	O
if	O
one	O
were	O
to	O
try	O
to	O
format	O
it	O
as	O
tabular	O
data	O
for	O
conventional	O
data	B-Application
mining	I-Application
,	O
large	O
sections	O
of	O
the	O
tables	O
would	O
or	O
could	O
be	O
empty	O
.	O
</s>
<s>
There	O
is	O
a	O
tacit	O
assumption	O
made	O
in	O
the	O
design	O
of	O
most	O
data	B-Application
mining	I-Application
algorithms	O
that	O
the	O
data	O
presented	O
will	O
be	O
complete	O
.	O
</s>
<s>
For	O
instance	O
methods	O
based	O
on	O
neural	B-Architecture
networks	I-Architecture
.	O
</s>
<s>
or	O
Ross	O
Quinlan	O
's	O
ID3	B-Algorithm
algorithm	I-Algorithm
.	O
</s>
<s>
A	O
particularly	O
relevant	O
area	O
where	O
finding	O
the	O
appropriate	O
structure	O
and	O
model	O
is	O
the	O
key	O
issue	O
is	O
text	B-Algorithm
mining	I-Algorithm
.	O
</s>
<s>
XPath	B-Language
is	O
the	O
standard	O
mechanism	O
used	O
to	O
refer	O
to	O
nodes	O
and	O
data	O
items	O
within	O
XML	B-Protocol
.	O
</s>
<s>
To	O
data	O
and	O
structure	O
mine	O
XML	B-Protocol
data	O
of	O
any	O
form	O
,	O
at	O
least	O
two	O
extensions	O
are	O
required	O
to	O
conventional	O
data	B-Application
mining	I-Application
.	O
</s>
<s>
These	O
are	O
the	O
ability	O
to	O
associate	O
an	O
XPath	B-Language
statement	O
with	O
any	O
data	O
pattern	O
and	O
sub	O
statements	O
with	O
each	O
data	O
node	O
in	O
the	O
data	O
pattern	O
,	O
and	O
the	O
ability	O
to	O
mine	O
the	O
presence	O
and	O
count	O
of	O
any	O
node	O
or	O
set	O
of	O
nodes	O
within	O
the	O
document	O
.	O
</s>
<s>
As	O
an	O
example	O
,	O
if	O
one	O
were	O
to	O
represent	O
a	O
family	O
tree	O
in	O
XML	B-Protocol
,	O
using	O
these	O
extensions	O
one	O
could	O
create	O
a	O
data	O
set	O
containing	O
all	O
the	O
individuals	O
node	O
in	O
the	O
tree	O
,	O
data	O
items	O
such	O
as	O
name	O
and	O
age	O
at	O
death	O
,	O
and	O
counts	O
of	O
related	O
nodes	O
,	O
such	O
as	O
number	O
of	O
children	O
.	O
</s>
<s>
The	O
addition	O
of	O
these	O
data	O
types	O
related	O
to	O
the	O
structure	O
of	O
a	O
document	O
or	O
message	O
facilitates	O
structure	B-Algorithm
mining	I-Algorithm
.	O
</s>
