<s>
Referring	B-General_Concept
expression	I-General_Concept
generation	I-General_Concept
(	O
REG	O
)	O
is	O
the	O
subtask	O
of	O
natural	B-General_Concept
language	I-General_Concept
generation	I-General_Concept
(	O
NLG	O
)	O
that	O
received	O
most	O
scholarly	O
attention	O
.	O
</s>
<s>
Graph	B-Algorithm
search	I-Algorithm
which	O
treats	O
relations	O
between	O
targets	O
in	O
the	O
same	O
way	O
as	O
properties	O
.	O
</s>
<s>
Constraint	B-Application
Satisfaction	I-Application
which	O
allows	O
for	O
a	O
separation	O
between	O
problem	O
specification	O
and	O
the	O
implementation	O
.	O
</s>
<s>
Modern	O
Knowledge	O
Representation	O
which	O
offers	O
logical	O
inference	O
in	O
for	O
example	O
Description	B-Language
Logic	I-Language
or	O
Conceptual	O
Graphs	O
.	O
</s>
<s>
Each	O
entity	O
in	O
the	O
domain	O
can	O
be	O
characterised	O
as	O
a	O
set	O
of	O
attribute	B-Application
–	I-Application
value	I-Application
pairs	I-Application
for	O
example	O
type	O
,	O
dog	O
,	O
gender	O
,	O
female	O
or	O
age	O
,	O
10	O
years	O
.	O
</s>
<s>
Then	O
,	O
a	O
set	O
of	O
attribute	B-Application
–	I-Application
value	I-Application
pairs	I-Application
will	O
represent	O
a	O
distinguishing	O
description	O
if	O
the	O
following	O
two	O
conditions	O
hold	O
:	O
</s>
<s>
Every	O
attribute	B-Application
–	I-Application
value	I-Application
pair	I-Application
in	O
applies	O
to	O
:	O
that	O
is	O
,	O
every	O
element	O
of	O
specifies	O
an	O
attribute	B-Application
–	I-Application
value	I-Application
that	O
possesses	O
.	O
</s>
<s>
For	O
every	O
member	O
of	O
,	O
there	O
is	O
at	O
least	O
one	O
element	O
of	O
that	O
does	O
not	O
apply	O
to	O
:	O
that	O
is	O
,	O
there	O
is	O
an	O
in	O
that	O
specifies	O
an	O
attribute	B-Application
–	I-Application
value	I-Application
that	O
does	O
not	O
possess	O
.	O
</s>
