<s>
Logtalk	B-Language
is	O
an	O
object-oriented	B-Language
logic	B-Language
programming	I-Language
language	I-Language
that	O
extends	O
and	O
leverages	O
the	O
Prolog	B-Language
language	I-Language
with	O
a	O
feature	O
set	O
suitable	O
for	O
programming	O
in	O
the	O
large	O
.	O
</s>
<s>
It	O
provides	O
support	O
for	O
encapsulation	B-Application
and	I-Application
data	I-Application
hiding	I-Application
,	O
separation	O
of	O
concerns	O
and	O
enhanced	O
code	O
reuse	O
.	O
</s>
<s>
Logtalk	B-Language
uses	O
standard	O
Prolog	B-Language
syntax	O
with	O
the	O
addition	O
of	O
a	O
few	O
operators	O
and	O
directives	O
.	O
</s>
<s>
The	O
Logtalk	B-Language
language	O
implementation	O
is	O
distributed	O
under	O
an	O
open	O
source	O
license	O
and	O
can	O
run	O
using	O
a	O
Prolog	B-Language
implementation	O
(	O
compliant	O
with	O
official	O
and	O
de	O
facto	O
standards	O
)	O
as	O
the	O
back-end	B-Architecture
compiler	O
.	O
</s>
<s>
Logtalk	B-Language
aims	O
to	O
bring	O
together	O
the	O
advantages	O
of	O
object-oriented	B-Language
programming	I-Language
and	O
logic	B-Language
programming	I-Language
.	O
</s>
<s>
Object-orientation	O
emphasizes	O
developing	O
discrete	O
,	O
reusable	O
units	O
of	O
software	O
,	O
while	O
logic	B-Language
programming	I-Language
emphasizes	O
representing	O
the	O
knowledge	O
of	O
each	O
object	O
in	O
a	O
declarative	O
way	O
.	O
</s>
<s>
As	O
an	O
object-oriented	B-Language
programming	I-Language
language	I-Language
,	O
Logtalk	B-Language
's	O
major	O
features	O
include	O
support	O
for	O
both	O
classes	O
(	O
with	O
optional	O
metaclasses	B-Language
)	O
and	O
prototypes	B-Application
,	O
parametric	O
objects	O
,	O
protocols	B-Application
(	O
interfaces	B-Application
)	O
,	O
categories	O
(	O
components	O
,	O
aspects	B-Architecture
,	O
hot	O
patching	O
)	O
,	O
multiple	B-Application
inheritance	I-Application
,	O
public/protected/private	O
inheritance	O
,	O
event-driven	B-Application
programming	I-Application
,	O
high-level	O
multi-threading	O
programming	O
,	O
reflection	B-Language
,	O
and	O
automatic	O
generation	O
of	O
documentation	O
.	O
</s>
<s>
For	O
Prolog	B-Language
programmers	O
,	O
Logtalk	B-Language
provides	O
wide	O
portability	O
,	O
featuring	O
predicate	O
namespaces	O
(	O
supporting	O
both	O
static	O
and	O
dynamic	O
objects	O
)	O
,	O
public/protected/private	O
object	O
predicates	O
,	O
coinductive	B-Application
predicates	I-Application
,	O
separation	O
between	O
interface	O
and	O
implementation	O
,	O
simple	O
and	O
intuitive	O
meta-predicate	O
semantics	O
,	O
lambda	B-Language
expressions	I-Language
,	O
definite	B-Application
clause	I-Application
grammars	I-Application
,	O
term-expansion	O
mechanism	O
,	O
and	O
conditional	O
compilation	O
.	O
</s>
<s>
It	O
also	O
provides	O
a	O
module	O
system	O
based	O
on	O
de	O
facto	O
standard	O
core	O
module	O
functionality	O
(	O
internally	O
,	O
modules	O
are	O
compiled	O
as	O
prototypes	B-Application
)	O
.	O
</s>
<s>
Logtalk	B-Language
's	O
syntax	O
is	O
based	O
on	O
Prolog	B-Language
:	O
</s>
<s>
Supported	O
back-end	B-Architecture
Prolog	B-Language
compilers	O
include	O
B-Prolog	B-Language
,	O
Ciao	B-Application
Prolog	I-Application
,	O
,	O
ECLiPSe	B-Application
,	O
GNU	B-Application
Prolog	I-Application
,	O
,	O
,	O
,	O
SICStus	B-Language
Prolog	I-Language
,	O
SWI-Prolog	B-Application
,	O
,	O
,	O
XSB	B-Language
,	O
and	O
YAP	B-Application
.	O
</s>
<s>
Logtalk	B-Language
allows	O
use	O
of	O
back-end	B-Architecture
Prolog	B-Language
compiler	O
libraries	O
from	O
within	O
object	O
and	O
categories	O
.	O
</s>
<s>
Logtalk	B-Language
features	O
on-line	O
help	O
,	O
a	O
documenting	O
tool	O
(	O
that	O
can	O
generate	O
PDF	O
and	O
HTML	O
files	O
)	O
,	O
an	O
entity	O
diagram	O
generator	O
tool	O
,	O
a	O
built-in	O
debugger	O
(	O
based	O
on	O
an	O
extended	O
version	O
of	O
the	O
traditional	O
Procedure	O
Box	O
model	O
found	O
on	O
most	O
Prolog	B-Language
compilers	O
)	O
,	O
a	O
unit	O
test	O
framework	O
with	O
code	O
coverage	O
analysis	O
,	O
and	O
is	O
also	O
compatible	O
with	O
selected	O
back-end	B-Architecture
Prolog	B-Language
profilers	O
and	O
graphical	O
tracers	O
.	O
</s>
<s>
Logtalk	B-Language
has	O
been	O
used	O
to	O
process	O
STEP	O
data	O
models	O
used	O
to	O
exchange	O
product	B-Application
manufacturing	I-Application
information	I-Application
.	O
</s>
<s>
It	O
has	O
also	O
been	O
used	O
to	O
implement	O
a	O
reasoning	O
system	O
that	O
allows	O
preference	O
reasoning	O
and	O
constraint	B-Application
solving	I-Application
.	O
</s>
