<s>
Conceptual	B-Algorithm
clustering	I-Algorithm
is	O
a	O
machine	O
learning	O
paradigm	O
for	O
unsupervised	B-General_Concept
classification	I-General_Concept
that	O
has	O
been	O
defined	O
by	O
Ryszard	O
S	O
.	O
Michalski	O
in	O
1980	O
(	O
Fisher	O
1987	O
,	O
Michalski	O
1980	O
)	O
and	O
developed	O
mainly	O
during	O
the	O
1980s	O
.	O
</s>
<s>
It	O
is	O
distinguished	O
from	O
ordinary	O
data	B-Algorithm
clustering	I-Algorithm
by	O
generating	O
a	O
concept	O
description	O
for	O
each	O
generated	O
class	O
.	O
</s>
<s>
Most	O
conceptual	B-Algorithm
clustering	I-Algorithm
methods	O
are	O
capable	O
of	O
generating	O
hierarchical	O
category	O
structures	O
;	O
see	O
Categorization	O
for	O
more	O
information	O
on	O
hierarchy	O
.	O
</s>
<s>
Conceptual	B-Algorithm
clustering	I-Algorithm
is	O
closely	O
related	O
to	O
formal	B-Algorithm
concept	I-Algorithm
analysis	I-Algorithm
,	O
decision	B-Algorithm
tree	I-Algorithm
learning	I-Algorithm
,	O
and	O
mixture	O
model	O
learning	O
.	O
</s>
<s>
Conceptual	B-Algorithm
clustering	I-Algorithm
is	O
obviously	O
closely	O
related	O
to	O
data	B-Algorithm
clustering	I-Algorithm
;	O
however	O
,	O
in	O
conceptual	B-Algorithm
clustering	I-Algorithm
it	O
is	O
not	O
only	O
the	O
inherent	O
structure	O
of	O
the	O
data	O
that	O
drives	O
cluster	O
formation	O
,	O
but	O
also	O
the	O
Description	B-Application
language	I-Application
which	O
is	O
available	O
to	O
the	O
learner	O
.	O
</s>
<s>
Thus	O
,	O
a	O
statistically	O
strong	O
grouping	O
in	O
the	O
data	O
may	O
fail	O
to	O
be	O
extracted	O
by	O
the	O
learner	O
if	O
the	O
prevailing	O
concept	O
description	B-Application
language	I-Application
is	O
incapable	O
of	O
describing	O
that	O
particular	O
regularity	O
.	O
</s>
<s>
In	O
most	O
implementations	O
,	O
the	O
description	B-Application
language	I-Application
has	O
been	O
limited	O
to	O
feature	O
conjunction	O
,	O
although	O
in	O
COBWEB	B-Algorithm
(	O
see	O
"	O
COBWEB	B-Algorithm
"	O
below	O
)	O
,	O
the	O
feature	O
language	O
is	O
probabilistic	O
.	O
</s>
<s>
A	O
fair	O
number	O
of	O
algorithms	O
have	O
been	O
proposed	O
for	O
conceptual	B-Algorithm
clustering	I-Algorithm
.	O
</s>
<s>
More	O
general	O
discussions	O
and	O
reviews	O
of	O
conceptual	B-Algorithm
clustering	I-Algorithm
can	O
be	O
found	O
in	O
the	O
following	O
publications	O
:	O
</s>
<s>
This	O
section	O
discusses	O
the	O
rudiments	O
of	O
the	O
conceptual	B-Algorithm
clustering	I-Algorithm
algorithm	O
COBWEB	B-Algorithm
.	O
</s>
<s>
There	O
are	O
many	O
other	O
algorithms	O
using	O
different	O
heuristics	O
and	O
"	O
category	B-General_Concept
goodness	I-General_Concept
"	O
or	O
category	O
evaluation	O
criteria	O
,	O
but	O
COBWEB	B-Algorithm
is	O
one	O
of	O
the	O
best	O
known	O
.	O
</s>
<s>
The	O
COBWEB	B-Algorithm
data	O
structure	O
is	O
a	O
hierarchy	O
(	O
tree	O
)	O
wherein	O
each	O
node	O
represents	O
a	O
given	O
concept	O
.	O
</s>
<s>
Each	O
concept	O
represents	O
a	O
set	O
(	O
actually	O
,	O
a	O
multiset	B-Language
or	O
bag	O
)	O
of	O
objects	O
,	O
each	O
object	O
being	O
represented	O
as	O
a	O
binary-valued	O
property	O
list	O
.	O
</s>
<s>
In	O
Fisher	O
's	O
(	O
1987	O
)	O
description	O
of	O
COBWEB	B-Algorithm
,	O
he	O
indicates	O
that	O
only	O
the	O
total	O
attribute	O
counts	O
(	O
not	O
conditional	O
probabilities	O
,	O
and	O
not	O
object	O
lists	O
)	O
are	O
stored	O
at	O
the	O
nodes	O
.	O
</s>
<s>
The	O
description	B-Application
language	I-Application
of	O
COBWEB	B-Algorithm
is	O
a	O
"	O
language	O
"	O
only	O
in	O
a	O
loose	O
sense	O
,	O
because	O
being	O
fully	O
probabilistic	O
it	O
is	O
capable	O
of	O
describing	O
any	O
concept	O
.	O
</s>
<s>
In	O
Fisher	O
's	O
(	O
1987	O
)	O
description	O
of	O
COBWEB	B-Algorithm
,	O
the	O
measure	O
he	O
uses	O
to	O
evaluate	O
the	O
quality	O
of	O
the	O
hierarchy	O
is	O
Gluck	O
and	O
Corter	O
's	O
(	O
1985	O
)	O
category	B-General_Concept
utility	I-General_Concept
(	O
CU	O
)	O
measure	O
,	O
which	O
he	O
re-derives	O
in	O
his	O
paper	O
.	O
</s>
<s>
The	O
motivation	O
for	O
the	O
measure	O
is	O
highly	O
similar	O
to	O
the	O
"	O
information	B-Algorithm
gain	I-Algorithm
"	O
measure	O
introduced	O
by	O
Quinlan	O
for	O
decision	B-Algorithm
tree	I-Algorithm
learning	I-Algorithm
.	O
</s>
