<s>
In	O
artificial	B-Application
intelligence	I-Application
,	O
action	B-Language
description	I-Language
language	I-Language
(	O
ADL	O
)	O
is	O
an	O
automated	B-Application
planning	I-Application
and	I-Application
scheduling	I-Application
system	O
in	O
particular	O
for	O
robots	O
.	O
</s>
<s>
It	O
is	O
considered	O
an	O
advancement	O
of	O
STRIPS	B-Application
.	O
</s>
<s>
It	O
is	O
an	O
example	O
of	O
an	O
action	B-Application
language	I-Application
.	O
</s>
<s>
Pednault	O
observed	O
that	O
the	O
expressive	O
power	O
of	O
STRIPS	B-Application
was	O
susceptible	O
to	O
being	O
improved	O
by	O
allowing	O
the	O
effects	O
of	O
an	O
operator	O
to	O
be	O
conditional	O
.	O
</s>
<s>
This	O
is	O
the	O
main	O
idea	O
of	O
ADL-A	B-Language
,	O
which	O
is	O
basically	O
the	O
propositional	O
fragment	O
of	O
the	O
ADL	O
proposed	O
by	O
Pednault	O
,	O
with	O
ADL-B	B-Language
an	O
extension	O
of	O
-A	O
.	O
</s>
<s>
A	O
third	O
variation	O
of	O
ADL	O
is	O
ADL-C	B-Language
which	O
is	O
similar	O
to	O
-B	O
,	O
in	O
the	O
sense	O
that	O
its	O
propositions	O
can	O
be	O
classified	O
into	O
static	O
and	O
dynamic	O
laws	O
,	O
but	O
with	O
some	O
more	O
particularities	O
.	O
</s>
<s>
Contrary	O
to	O
STRIPS	B-Application
,	O
the	O
principle	O
of	O
the	O
open	B-Application
world	I-Application
applies	O
with	O
ADL	O
:	O
everything	O
not	O
occurring	O
in	O
the	O
conditions	O
is	O
unknown	O
(	O
Instead	O
of	O
being	O
assumed	O
false	O
)	O
.	O
</s>
<s>
In	O
addition	O
,	O
whereas	O
in	O
STRIPS	B-Application
only	O
positive	O
literals	O
and	O
conjunctions	O
are	O
permitted	O
,	O
ADL	O
allows	O
negative	O
literals	O
and	O
disjunctions	O
as	O
well	O
.	O
</s>
<s>
In	O
terms	O
of	O
computational	O
efficiency	O
,	O
ADL	O
can	O
be	O
located	O
between	O
STRIPS	B-Application
and	O
the	O
Situation	O
Calculus	O
.	O
</s>
<s>
Any	O
ADL	O
problem	O
can	O
be	O
translated	O
into	O
a	O
STRIPS	B-Application
instance	O
–	O
however	O
,	O
existing	O
compilation	O
techniques	O
are	O
worst-case	O
exponential	O
.	O
</s>
<s>
This	O
worst	O
case	O
cannot	O
be	O
improved	O
if	O
we	O
are	O
willing	O
to	O
preserve	O
the	O
length	O
of	O
plans	O
polynomially	O
,	O
and	O
thus	O
ADL	O
is	O
strictly	O
more	O
brief	O
than	O
STRIPS	B-Application
.	O
</s>
<s>
Most	O
of	O
the	O
top-performing	O
approaches	O
to	O
classical	O
planning	O
internally	O
utilize	O
a	O
STRIPS	B-Application
like	O
representation	O
.	O
</s>
<s>
In	O
fact	O
most	O
of	O
the	O
planners	O
(	O
FF	O
,	O
LPG	O
,	O
Fast-Downward	O
,	O
SGPLAN5	O
and	O
LAMA	O
)	O
first	O
translate	O
the	O
ADL	O
instance	O
into	O
one	O
that	O
is	O
essentially	O
a	O
STRIPS	B-Application
one	O
(	O
without	O
conditional	O
or	O
quantified	O
effects	O
or	O
goals	O
)	O
.	O
</s>
<s>
The	O
STRIPS	B-Application
language	O
only	O
allows	O
positive	O
literals	O
in	O
the	O
states	O
,	O
while	O
ADL	O
can	O
support	O
both	O
positive	O
and	O
negative	O
literals	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
valid	O
sentence	O
in	O
STRIPS	B-Application
could	O
be	O
Rich∧Beautiful	O
.	O
</s>
<s>
In	O
STRIPS	B-Application
the	O
unmentioned	O
literals	O
are	O
false	O
.	O
</s>
<s>
This	O
is	O
called	O
the	O
closed-world	B-Application
assumption	I-Application
.	O
</s>
<s>
This	O
is	O
known	O
as	O
the	O
Open	B-Application
World	I-Application
Assumption	I-Application
.	O
</s>
<s>
In	O
STRIPS	B-Application
we	O
only	O
can	O
find	O
ground	O
literals	O
in	O
goals	O
.	O
</s>
<s>
In	O
STRIPS	B-Application
the	O
goals	O
are	O
conjunctions	O
,	O
e.g.	O
,	O
(	O
Rich	O
∧	O
Beautiful	O
)	O
.	O
</s>
<s>
The	O
STRIPS	B-Application
language	O
does	O
not	O
support	O
equality	O
.	O
</s>
<s>
STRIPS	B-Application
does	O
not	O
have	O
support	O
for	O
types	O
,	O
while	O
in	O
ADL	O
it	O
is	O
supported	O
(	O
for	O
example	O
,	O
the	O
variable	O
p	O
:	O
Person	O
)	O
.	O
</s>
<s>
The	O
expressiveness	O
of	O
the	O
STRIPS	B-Application
language	O
is	O
constrained	O
by	O
the	O
types	O
of	O
transformations	O
on	O
sets	O
of	O
formulas	O
that	O
can	O
be	O
described	O
in	O
the	O
language	O
.	O
</s>
<s>
Transformations	O
on	O
sets	O
of	O
formulas	O
using	O
STRIPS	B-Application
operators	O
are	O
accomplished	O
by	O
removing	O
some	O
formulas	O
from	O
the	O
set	O
to	O
be	O
transformed	O
and	O
adding	O
new	O
additional	O
formulas	O
.	O
</s>
<s>
For	O
a	O
given	O
STRIPS	B-Application
operator	O
the	O
formulas	O
to	O
be	O
added	O
and	O
deleted	O
are	O
fixed	O
for	O
all	O
sets	O
of	O
formulas	O
to	O
be	O
transformed	O
.	O
</s>
<s>
Consequently	O
,	O
STRIPS	B-Application
operators	O
cannot	O
adequately	O
model	O
actions	O
whose	O
effects	O
depend	O
on	O
the	O
situations	O
in	O
which	O
they	O
are	O
performed	O
.	O
</s>
<s>
It	O
cannot	O
be	O
modelled	O
by	O
means	O
of	O
a	O
STRIPS	B-Application
operator	O
because	O
the	O
formulas	O
that	O
would	O
have	O
to	O
be	O
added	O
and	O
deleted	O
would	O
depend	O
on	O
the	O
set	O
of	O
formulas	O
to	O
be	O
transformed	O
.	O
</s>
<s>
Although	O
an	O
efficient	O
reasoning	O
is	O
possible	O
when	O
the	O
STRIPS	B-Application
language	O
is	O
being	O
used	O
it	O
is	O
generally	O
recognized	O
that	O
the	O
expressiveness	O
of	O
STRIPS	B-Application
is	O
not	O
suitable	O
for	O
modeling	O
actions	O
in	O
many	O
real	O
world	O
applications	O
.	O
</s>
<s>
ADL	O
expressiveness	O
and	O
complexity	O
lies	O
between	O
the	O
STRIPS	B-Application
language	O
and	O
the	O
situation	O
calculus	O
.	O
</s>
<s>
As	O
an	O
example	O
in	O
a	O
more	O
complex	O
version	O
of	O
the	O
blocks	O
world	O
:	O
It	O
could	O
be	O
that	O
block	O
A	B-Application
is	I-Application
twice	O
as	O
big	O
as	O
blocks	O
B	O
and	O
C	O
,	O
so	O
the	O
action	O
xMoveOnto(B,A )	O
might	O
only	O
have	O
the	O
effect	O
of	O
negating	O
Clear(A )	O
if	O
On(A,C )	O
is	O
already	O
true	O
,	O
or	O
creating	O
the	O
conditional	O
effect	O
depending	O
on	O
the	O
size	O
of	O
the	O
blocks	O
.	O
</s>
<s>
This	O
kind	O
of	O
conditional	O
effects	O
would	O
be	O
hard	O
to	O
express	O
in	O
STRIPS	B-Application
notation	O
without	O
the	O
conditional	O
effects	O
.	O
</s>
