<s>
In	O
artificial	B-Application
intelligence	I-Application
and	O
cognitive	O
science	O
,	O
the	O
structure	B-General_Concept
mapping	I-General_Concept
engine	I-General_Concept
(	O
SME	O
)	O
is	O
an	O
implementation	O
in	O
software	O
of	O
an	O
algorithm	O
for	O
analogical	O
matching	O
based	O
on	O
the	O
psychological	O
theory	O
of	O
Dedre	O
Gentner	O
.	O
</s>
<s>
The	O
structure-mapping	O
engine	O
is	O
a	O
computer	B-Application
simulation	I-Application
of	O
the	O
analogy	O
and	O
similarity	O
comparisons	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
structure	B-General_Concept
mapping	I-General_Concept
engine	I-General_Concept
should	O
ignore	O
isolated	O
source-target	O
mappings	O
unless	O
they	O
are	O
part	O
of	O
a	O
bigger	O
structure	O
.	O
</s>
<s>
The	O
theory	O
also	O
requires	O
that	O
mappings	O
be	O
done	O
one-to-one	B-Algorithm
,	O
which	O
means	O
that	O
no	O
part	O
of	O
the	O
source	O
description	O
can	O
map	O
to	O
more	O
than	O
one	O
item	O
in	O
the	O
target	O
and	O
no	O
part	O
of	O
the	O
target	O
description	O
can	O
be	O
mapped	O
to	O
more	O
than	O
one	O
part	O
of	O
the	O
source	O
.	O
</s>
<s>
Dgroups	O
contain	O
a	O
list	O
of	O
entities	O
and	O
predicates	B-Algorithm
.	O
</s>
<s>
Predicates	B-Algorithm
are	O
one	O
of	O
three	O
types	O
and	O
are	O
a	O
general	O
way	O
to	O
express	O
knowledge	O
for	O
SME	O
.	O
</s>
<s>
Relation	O
predicates	B-Algorithm
contain	O
multiple	O
arguments	O
,	O
which	O
can	O
be	O
other	O
predicates	B-Algorithm
or	O
entities	O
.	O
</s>
<s>
This	O
relation	O
has	O
a	O
functor	B-Language
transmit	O
and	O
takes	O
three	O
arguments	O
:	O
what	O
,	O
from	O
,	O
and	O
to	O
.	O
</s>
<s>
Attribute	B-General_Concept
predicates	B-Algorithm
are	O
the	O
properties	O
of	O
an	O
entity	O
.	O
</s>
<s>
An	O
example	O
of	O
an	O
attribute	B-General_Concept
is	O
(	O
red	O
gear	O
)	O
which	O
means	O
that	O
gear	O
has	O
the	O
attribute	B-General_Concept
red	O
.	O
</s>
<s>
Function	O
predicates	B-Algorithm
map	O
an	O
entity	O
into	O
another	O
entity	O
or	O
constant	O
.	O
</s>
<s>
An	O
example	O
of	O
a	O
function	O
is	O
(	O
joules	B-Language
power	O
source	O
)	O
which	O
maps	O
the	O
entity	O
power	O
source	O
onto	O
the	O
numerical	O
quantity	O
joules	B-Language
.	O
</s>
<s>
All	O
predicates	B-Algorithm
have	O
four	O
parameters	O
.	O
</s>
<s>
They	O
have	O
(	O
1	O
)	O
a	O
functor	B-Language
,	O
which	O
identifies	O
it	O
,	O
and	O
(	O
2	O
)	O
a	O
type	O
,	O
which	O
is	O
either	O
relation	O
,	O
attribute	B-General_Concept
,	O
or	O
function	O
.	O
</s>
<s>
The	O
predicate	O
’s	O
functor	B-Language
is	O
“	O
behavior-set	O
,	O
”	O
its	O
type	O
is	O
“	O
relation	O
,	O
”	O
and	O
its	O
n-ary	O
and	O
commutative	O
parameters	O
are	O
both	O
set	O
to	O
true	O
.	O
</s>
<s>
The	O
“	O
(	O
predicate	O
)	O
”	O
part	O
of	O
the	O
definition	O
specifies	O
that	O
there	O
will	O
be	O
one	O
or	O
more	O
predicates	B-Algorithm
inside	O
an	O
instantiation	O
of	O
behavior-set	O
.	O
</s>
<s>
An	O
example	O
of	O
a	O
filter	O
rule	O
from	O
the	O
true-analogy	O
rule	O
set	O
creates	O
match	O
hypotheses	O
between	O
predicates	B-Algorithm
that	O
have	O
the	O
same	O
functor	B-Language
.	O
</s>
<s>
The	O
true-analogy	O
rule	O
set	O
has	O
an	O
intern	O
rule	O
that	O
iterates	O
over	O
the	O
arguments	O
of	O
any	O
match	O
hypothesis	O
,	O
creating	O
more	O
match	O
hypotheses	O
if	O
the	O
arguments	O
are	O
entities	O
or	O
functions	O
,	O
or	O
if	O
the	O
arguments	O
are	O
attributes	O
and	O
have	O
the	O
same	O
functor	B-Language
.	O
</s>
<s>
In	O
order	O
to	O
illustrate	O
how	O
the	O
match	O
rules	O
produce	O
match	O
hypotheses	O
consider	O
these	O
two	O
predicates	B-Algorithm
:	O
</s>
<s>
The	O
filter	O
match	O
rule	O
generates	O
a	O
match	O
between	O
p1	O
and	O
p2	O
because	O
they	O
share	O
the	O
same	O
functor	B-Language
,	O
transmit	O
.	O
</s>
<s>
If	O
the	O
arguments	O
were	O
functions	O
or	O
attributes	O
instead	O
of	O
entities	O
,	O
the	O
predicates	B-Algorithm
would	O
be	O
expressed	O
as	O
:	O
</s>
<s>
These	O
additional	O
predicates	B-Algorithm
make	O
inputgear	O
,	O
secondgear	O
,	O
switch	O
,	O
and	O
div10	O
functions	O
or	O
attributes	O
depending	O
on	O
the	O
value	O
defined	O
in	O
the	O
language	O
input	O
file	O
.	O
</s>
<s>
When	O
the	O
additional	O
predicates	B-Algorithm
in	O
p3	O
and	O
p4	O
are	O
functions	O
,	O
the	O
results	O
from	O
matching	O
p3	O
and	O
p4	O
are	O
similar	O
to	O
the	O
results	O
from	O
p1	O
and	O
p2	O
except	O
there	O
is	O
an	O
additional	O
match	O
between	O
gear	O
and	O
circuit	O
and	O
the	O
values	O
for	O
the	O
match	O
hypotheses	O
between	O
(	O
inputgear	O
gear	O
)	O
and	O
(	O
switch	O
circuit	O
)	O
,	O
and	O
(	O
secondgear	O
gear	O
)	O
and	O
(	O
div10	O
circuit	O
)	O
,	O
are	O
lower	O
.	O
</s>
<s>
It	O
finds	O
matches	O
only	O
between	O
the	O
transmit	O
predicates	B-Algorithm
and	O
between	O
torque	O
and	O
signal	O
.	O
</s>
<s>
In	O
order	O
to	O
get	O
the	O
two	O
predicates	B-Algorithm
to	O
match	O
,	O
p3	O
would	O
need	O
to	O
be	O
replaced	O
by	O
p5	O
,	O
which	O
is	O
demonstrated	O
below	O
.	O
</s>
<s>
If	O
the	O
source	O
and	O
target	O
have	O
the	O
same	O
functor	B-Language
,	O
the	O
match	O
gets	O
0.2	O
evidence	O
if	O
the	O
source	O
is	O
a	O
function	O
and	O
0.5	O
if	O
the	O
source	O
is	O
a	O
relation	O
.	O
</s>
<s>
The	O
arguments	O
might	O
match	O
if	O
all	O
the	O
pairs	O
of	O
arguments	O
between	O
the	O
source	O
and	O
target	O
are	O
entities	O
,	O
if	O
the	O
arguments	O
have	O
the	O
same	O
functors	B-Language
,	O
or	O
it	O
is	O
never	O
the	O
case	O
that	O
the	O
target	O
is	O
an	O
entity	O
but	O
the	O
source	O
is	O
not	O
.	O
</s>
<s>
For	O
predicates	B-Algorithm
p3	O
and	O
p4	O
,	O
SME	O
assigns	O
less	O
evidence	O
because	O
the	O
arguments	O
of	O
the	O
transmit	O
relations	O
are	O
functions	O
.	O
</s>
<s>
When	O
the	O
predicates	B-Algorithm
in	O
p3	O
and	O
p4	O
are	O
attributes	O
,	O
rule	O
4	O
adds	O
-0.8	O
evidence	O
to	O
the	O
transmit	O
match	O
because	O
—	O
though	O
the	O
functors	B-Language
of	O
the	O
transmit	O
relation	O
match	O
—	O
the	O
arguments	O
do	O
not	O
have	O
the	O
potential	O
to	O
match	O
and	O
the	O
arguments	O
are	O
not	O
functions	O
.	O
</s>
<s>
Rule	O
2	O
adds	O
support	O
for	O
the	O
cases	O
when	O
the	O
functors	B-Language
match	O
.	O
</s>
<s>
Attributes	O
are	O
not	O
specifically	O
dealt	O
with	O
by	O
the	O
intern	O
match	O
rules	O
,	O
but	O
SME	O
’s	O
filter	O
rules	O
ensure	O
that	O
they	O
will	O
only	O
be	O
considered	O
for	O
these	O
rules	O
if	O
they	O
are	O
part	O
of	O
a	O
higher-order	O
relation	O
,	O
and	O
rule	O
2	O
ensures	O
that	O
attributes	O
will	O
only	O
match	O
if	O
they	O
have	O
identical	O
functors	B-Language
.	O
</s>
<s>
SME	O
must	O
ensure	O
that	O
any	O
gmaps	O
that	O
it	O
creates	O
are	O
structurally	O
consistent	O
;	O
in	O
other	O
words	O
,	O
that	O
they	O
are	O
one-to-one	B-Algorithm
—	O
such	O
that	O
no	O
source	O
maps	O
to	O
multiple	O
targets	O
and	O
no	O
target	O
is	O
mapped	O
to	O
multiple	O
sources	O
.	O
</s>
<s>
SME	O
then	O
uses	O
this	O
information	O
to	O
merge	O
match	O
hypotheses	O
—	O
using	O
a	O
greedy	B-Algorithm
algorithm	I-Algorithm
and	O
the	O
structural	O
evaluation	O
score	O
.	O
</s>
<s>
The	O
gmaps	O
show	O
pairs	O
of	O
predicates	B-Algorithm
or	O
entities	O
that	O
match	O
.	O
</s>
<s>
Although	O
p2	O
is	O
compatible	O
with	O
both	O
p1	O
and	O
p6	O
,	O
the	O
one-to-one	B-Algorithm
mapping	O
constraint	O
enforces	O
that	O
both	O
mappings	O
cannot	O
be	O
in	O
the	O
same	O
gmap	O
.	O
</s>
<s>
Chalmers	O
,	O
French	O
,	O
and	O
Hofstadter	O
 [ 1992 ] 	O
criticize	O
SME	O
for	O
its	O
reliance	O
on	O
manually	O
constructed	O
LISP	B-Language
representations	O
as	O
input	O
.	O
</s>
<s>
Turney	O
 [ 2008 ] 	O
presents	O
an	O
algorithm	O
that	O
does	O
not	O
require	O
LISP	B-Language
input	O
,	O
yet	O
follows	O
the	O
principles	O
of	O
Structure	O
Mapping	O
Theory	O
.	O
</s>
