<s>
The	O
terms	O
schema	B-General_Concept
matching	I-General_Concept
and	O
mapping	B-General_Concept
are	O
often	O
used	O
interchangeably	O
for	O
a	O
database	O
process	O
.	O
</s>
<s>
For	O
this	O
article	O
,	O
we	O
differentiate	O
the	O
two	O
as	O
follows	O
:	O
Schema	B-General_Concept
matching	I-General_Concept
is	O
the	O
process	O
of	O
identifying	O
that	O
two	O
objects	O
are	O
semantically	O
related	O
(	O
scope	O
of	O
this	O
article	O
)	O
while	O
mapping	B-General_Concept
refers	O
to	O
the	O
transformations	B-General_Concept
between	O
the	O
objects	O
.	O
</s>
<s>
and	O
possible	O
transformations	B-General_Concept
or	O
mappings	O
would	O
be	O
:	O
DB1.Marks	O
to	O
DB2.Grades	O
(	O
100-90	O
A	O
;	O
90-80	O
B	O
:	O
etc	O
.	O
</s>
<s>
Automating	O
these	O
two	O
approaches	O
has	O
been	O
one	O
of	O
the	O
fundamental	O
tasks	O
of	O
data	B-General_Concept
integration	I-General_Concept
.	O
</s>
<s>
In	O
general	O
,	O
it	O
is	O
not	O
possible	O
to	O
determine	O
fully	O
automatically	O
the	O
different	O
correspondences	O
between	O
two	O
schemas	B-Application
—	O
primarily	O
because	O
of	O
the	O
differing	O
and	O
often	O
not	O
explicated	O
or	O
documented	O
semantics	O
of	O
the	O
two	O
schemas	B-Application
.	O
</s>
<s>
Among	O
others	O
,	O
common	O
challenges	O
to	O
automating	O
matching	O
and	O
mapping	B-General_Concept
have	O
been	O
previously	O
classified	O
in	O
especially	O
for	O
relational	O
DB	O
schemas	B-Application
;	O
and	O
in	O
–	O
a	O
fairly	O
comprehensive	O
list	O
of	O
heterogeneity	O
not	O
limited	O
to	O
the	O
relational	O
model	O
recognizing	O
schematic	O
vs	O
semantic	O
differences/heterogeneity	O
.	O
</s>
<s>
Most	O
of	O
these	O
heterogeneities	O
exist	O
because	O
schemas	B-Application
use	O
different	O
representations	O
or	O
definitions	O
to	O
represent	O
the	O
same	O
information	O
(	O
schema	B-Application
conflicts	O
)	O
;	O
OR	O
different	O
expressions	O
,	O
units	O
,	O
and	O
precision	O
result	O
in	O
conflicting	O
representations	O
of	O
the	O
same	O
data	O
(	O
data	O
conflicts	O
)	O
.	O
</s>
<s>
Research	O
in	O
schema	B-General_Concept
matching	I-General_Concept
seeks	O
to	O
provide	O
automated	O
support	O
to	O
the	O
process	O
of	O
finding	O
semantic	O
matches	O
between	O
two	O
schemas	B-Application
.	O
</s>
<s>
Discusses	O
a	O
generic	O
methodology	O
for	O
the	O
task	O
of	O
schema	B-Application
integration	O
or	O
the	O
activities	O
involved	O
.	O
</s>
<s>
Preintegration	O
—	O
An	O
analysis	O
of	O
schemas	B-Application
is	O
carried	O
out	O
before	O
integration	O
to	O
decide	O
upon	O
some	O
integration	O
policy	O
.	O
</s>
<s>
This	O
governs	O
the	O
choice	O
of	O
schemas	B-Application
to	O
be	O
integrated	O
,	O
the	O
order	O
of	O
integration	O
,	O
and	O
a	O
possible	O
assignment	O
of	O
preferences	O
to	O
entire	O
schemas	B-Application
or	O
portions	O
of	O
schemas	B-Application
.	O
</s>
<s>
Comparison	O
of	O
the	O
Schemas	B-Application
—	O
Schemas	B-Application
are	O
analyzed	O
and	O
compared	O
to	O
determine	O
the	O
correspondences	O
among	O
concepts	O
and	O
detect	O
possible	O
conflicts	O
.	O
</s>
<s>
Interschema	O
properties	O
may	O
be	O
discovered	O
while	O
comparing	O
schemas	B-Application
.	O
</s>
<s>
Conforming	O
the	O
Schemas	B-Application
—	O
Once	O
conflicts	O
are	O
detected	O
,	O
an	O
effort	O
is	O
made	O
to	O
resolve	O
them	O
so	O
that	O
the	O
merging	O
of	O
various	O
schemas	B-Application
is	O
possible	O
.	O
</s>
<s>
Merging	O
and	O
Restructuring	O
—	O
Now	O
the	O
schemas	B-Application
are	O
ready	O
to	O
be	O
superimposed	O
,	O
giving	O
rise	O
to	O
some	O
intermediate	O
integrated	O
schema(s )	O
.	O
</s>
<s>
Approaches	O
to	O
schema	B-Application
integration	O
can	O
be	O
broadly	O
classified	O
as	O
ones	O
that	O
exploit	O
either	O
just	O
schema	B-Application
information	O
or	O
schema	B-Application
and	O
instance	O
level	O
information	O
.	O
</s>
<s>
Schema-level	O
matchers	O
only	O
consider	O
schema	B-Application
information	O
,	O
not	O
instance	O
data	O
.	O
</s>
<s>
The	O
available	O
information	O
includes	O
the	O
usual	O
properties	O
of	O
schema	B-Application
elements	O
,	O
such	O
as	O
name	O
,	O
description	O
,	O
data	O
type	O
,	O
relationship	O
types	O
(	O
part-of	O
,	O
is-a	O
,	O
etc	O
.	O
</s>
<s>
)	O
,	O
constraints	O
,	O
and	O
schema	B-Application
structure	O
.	O
</s>
<s>
Working	O
at	O
the	O
element	O
(	O
atomic	O
elements	O
like	O
attributes	O
of	O
objects	O
)	O
or	O
structure	O
level	O
(	O
matching	O
combinations	O
of	O
elements	O
that	O
appear	O
together	O
in	O
a	O
structure	O
)	O
,	O
these	O
properties	O
are	O
used	O
to	O
identify	O
matching	O
elements	O
in	O
two	O
schemas	B-Application
.	O
</s>
<s>
Language-based	O
or	O
linguistic	O
matchers	O
use	O
names	O
and	O
text	O
(	O
i.e.	O
,	O
words	O
or	O
sentences	O
)	O
to	O
find	O
semantically	O
similar	O
schema	B-Application
elements	O
.	O
</s>
<s>
Constraint	O
based	O
matchers	O
exploit	O
constraints	O
often	O
contained	O
in	O
schemas	B-Application
.	O
</s>
<s>
Constraints	O
in	O
two	O
input	O
schemas	B-Application
are	O
matched	O
to	O
determine	O
the	O
similarity	O
of	O
the	O
schema	B-Application
elements	O
.	O
</s>
<s>
Instance-level	O
matchers	O
use	O
instance-level	O
data	O
to	O
gather	O
important	O
insight	O
into	O
the	O
contents	O
and	O
meaning	O
of	O
the	O
schema	B-Application
elements	O
.	O
</s>
<s>
These	O
are	O
typically	O
used	O
in	O
addition	O
to	O
schema	B-Application
level	O
matches	O
in	O
order	O
to	O
boost	O
the	O
confidence	O
in	O
match	O
results	O
,	O
more	O
so	O
when	O
the	O
information	O
available	O
at	O
the	O
schema	B-Application
level	O
is	O
insufficient	O
.	O
</s>
<s>
The	O
motivation	O
for	O
this	O
work	O
is	O
that	O
structures	O
or	O
substructures	O
often	O
repeat	O
,	O
for	O
example	O
in	O
schemas	B-Application
in	O
the	O
E-commerce	O
domain	O
.	O
</s>
<s>
It	O
is	O
possible	O
that	O
such	O
a	O
reuse	O
makes	O
sense	O
only	O
for	O
some	O
part	O
of	O
a	O
new	O
schema	B-Application
or	O
only	O
in	O
some	O
domains	O
.	O
</s>
<s>
Among	O
others	O
,	O
an	O
early	O
attempt	O
to	O
use	O
description	O
logics	O
for	O
schema	B-Application
integration	O
and	O
identifying	O
such	O
relationships	O
was	O
presented	O
.	O
</s>
<s>
The	O
quality	O
of	O
schema	B-General_Concept
matching	I-General_Concept
is	O
commonly	O
measured	O
by	O
precision	O
and	O
recall	O
.	O
</s>
