<s>
SableVM	B-Language
was	O
a	O
clean	O
room	O
implementation	O
of	O
Java	B-Language
bytecode	O
interpreter	B-Application
implementing	O
the	O
Java	B-Language
virtual	I-Language
machine	I-Language
(	O
VM	B-Architecture
)	O
specification	O
,	O
second	O
edition	O
.	O
</s>
<s>
SableVM	B-Language
was	O
designed	O
to	O
be	O
a	O
robust	O
,	O
extremely	O
portable	O
,	O
efficient	O
,	O
and	O
fully	O
specifications-compliant	O
(	O
JVM	B-Language
spec	O
,	O
Java	B-Language
Native	I-Language
Interface	I-Language
,	O
Invocation	O
interface	O
,	O
Debug	O
interface	O
,	O
etc	O
.	O
)	O
</s>
<s>
Java	B-Language
Virtual	I-Language
Machine	I-Language
that	O
would	O
be	O
easy	O
to	O
maintain	O
and	O
to	O
extend	O
.	O
</s>
<s>
The	O
implementation	O
was	O
a	O
part	O
of	O
the	O
effort	O
in	O
the	O
early	O
2000s	O
to	O
break	O
the	O
Java	B-Language
ecosystem	O
free	O
from	O
Sun	O
Microsystems	O
's	O
control	O
.	O
</s>
<s>
The	O
core	O
engine	O
is	O
an	O
interpreter	B-Application
which	O
used	O
ground-breaking	O
techniques	O
to	O
deliver	O
performance	O
that	O
can	O
approach	O
that	O
of	O
a	O
"	O
naive	O
"	O
just-in-time	O
(	O
JIT	O
)	O
compiler	O
,	O
while	O
retaining	O
the	O
software	B-General_Concept
engineering	I-General_Concept
advantages	O
of	O
interpreters	B-Application
:	O
portability	O
,	O
maintainability	O
and	O
simplicity	O
.	O
</s>
<s>
This	O
simplicity	O
makes	O
SableVM	B-Language
's	O
source	O
code	O
very	O
accessible	O
and	O
easy	O
to	O
understand	O
for	O
new	O
users/programmers	O
.	O
</s>
<s>
SableVM	B-Language
is	O
Free	B-Application
Software	I-Application
—	O
it	O
is	O
licensed	O
under	O
the	O
GNU	B-Application
Lesser	I-Application
General	I-Application
Public	I-Application
License	I-Application
(	O
LGPL	B-Application
)	O
.	O
</s>
<s>
It	O
also	O
makes	O
use	O
of	O
GNU	B-Language
Classpath	I-Language
(	O
copyrighted	O
by	O
the	O
FSF	B-Operating_System
)	O
which	O
is	O
licensed	O
under	O
the	O
GNU	B-Application
General	I-Application
Public	I-Application
License	I-Application
with	I-Application
linking	I-Application
exception	I-Application
.	O
</s>
<s>
SableVM	B-Language
is	O
the	O
first	O
open-source	B-Application
virtual	B-Architecture
machine	I-Architecture
for	O
Java	B-Language
to	O
include	O
the	O
support	O
for	O
JVMDI	B-Language
(	O
Java	B-Language
Virtual	I-Language
Machine	I-Language
Debugging	O
Interface	O
)	O
and	O
JDWP	B-Language
(	O
Java	B-Language
Debug	I-Language
Wire	I-Language
Protocol	I-Language
)	O
.	O
</s>
<s>
These	O
standard	O
Java	B-Language
debugging	O
interfaces	O
are	O
used	O
for	O
example	O
by	O
Eclipse	B-Application
to	O
provide	O
a	O
rich	O
and	O
user-friendly	O
Java	B-Language
development	O
environment	O
.	O
</s>
<s>
Some	O
versions	O
of	O
the	O
SableVM	B-Language
use	O
Java	B-Language
Intermediate	I-Language
Language	I-Language
,	O
an	O
intermediate	O
language	O
(	O
which	O
is	O
a	O
subset	O
of	O
XML	B-Protocol
)	O
representing	O
the	O
type	O
structure	O
of	O
a	O
Java	B-Language
program	O
.	O
</s>
<s>
The	O
language	O
was	O
proposed	O
by	O
the	O
team	O
of	O
SableVM	B-Language
in	O
McGill	O
University	O
in	O
January	O
2002	O
to	O
aid	O
the	O
analysis	O
of	O
a	O
Java	B-Language
program	O
with	O
the	O
goals	O
of	O
scalability	O
and	O
good	O
performance	O
.	O
</s>
<s>
Consider	O
the	O
following	O
piece	O
of	O
Java	B-Language
code	I-Language
.	O
</s>
