<s>
The	O
Dynamic	B-Application
Language	I-Application
Runtime	I-Application
(	O
DLR	O
)	O
from	O
Microsoft	O
runs	O
on	O
top	O
of	O
the	O
Common	O
Language	O
Runtime	O
(	O
CLR	O
)	O
and	O
provides	O
computer	B-Language
language	I-Language
services	O
for	O
dynamic	B-Language
languages	I-Language
.	O
</s>
<s>
The	O
DLR	O
is	O
used	O
to	O
implement	O
dynamic	B-Language
languages	I-Language
on	O
the	O
.NET	B-Application
Framework	I-Application
,	O
including	O
the	O
IronPython	B-Application
and	O
IronRuby	B-Language
projects	O
.	O
</s>
<s>
Because	O
the	O
dynamic	B-Language
language	I-Language
implementations	O
share	O
a	O
common	O
underlying	O
system	O
,	O
it	O
should	O
be	O
easier	O
for	O
them	O
to	O
interact	O
with	O
one	O
another	O
.	O
</s>
<s>
For	O
example	O
,	O
it	O
should	O
be	O
possible	O
to	O
use	O
libraries	O
from	O
any	O
dynamic	B-Language
language	I-Language
in	O
any	O
other	O
dynamic	B-Language
language	I-Language
.	O
</s>
<s>
In	O
addition	O
,	O
the	O
hosting	O
API	O
allows	O
interoperability	O
with	O
statically	O
typed	O
CLI	B-Language
languages	I-Language
like	O
C#	B-Application
and	O
Visual	B-Language
Basic	I-Language
.NET	I-Language
.	O
</s>
<s>
Microsoft	O
's	O
Dynamic	B-Application
Language	I-Application
Runtime	I-Application
project	O
was	O
announced	O
by	O
Microsoft	O
at	O
MIX	O
2007	O
.	O
</s>
<s>
Microsoft	O
shipped	O
.NET	B-Application
DLR	O
0.9	O
beta	O
in	O
November	O
2008	O
,	O
and	O
final	O
0.9	O
in	O
December	O
2008	O
.	O
</s>
<s>
In	O
July	O
2010	O
,	O
Microsoft	O
changed	O
the	O
license	O
of	O
the	O
DLR	O
from	O
the	O
Microsoft	O
Public	O
License	O
to	O
the	O
Apache	B-Application
License	I-Application
2.0	I-Application
.	O
</s>
<s>
With	O
the	O
release	O
of	O
.NET	B-Application
4	O
,	O
also	O
in	O
April	O
2010	O
,	O
DLR	O
was	O
incorporated	O
into	O
the	O
.NET	B-Application
Framework	I-Application
itself	O
.	O
</s>
<s>
The	O
open	O
source	O
DLR	O
project	O
hosted	O
on	O
GitHub	B-Application
has	O
a	O
few	O
additional	O
features	O
for	O
language	O
implementers	O
.	O
</s>
<s>
This	O
was	O
interpreted	O
by	O
a	O
Microsoft	O
developer	O
who	O
worked	O
on	O
IronRuby	B-Language
as	O
a	O
lack	O
of	O
commitment	O
from	O
Microsoft	O
to	O
dynamic	B-Language
languages	I-Language
on	O
the	O
.NET	B-Application
Framework	I-Application
.	O
</s>
<s>
The	O
DLR	O
services	O
are	O
currently	O
used	O
in	O
the	O
development	O
version	O
of	O
IronRuby	B-Language
,	O
a	O
.NET	B-Application
implementation	O
of	O
the	O
Ruby	B-Language
language	I-Language
,	O
and	O
for	O
IronPython	B-Application
.	O
</s>
<s>
In	O
2007	O
,	O
Microsoft	O
planned	O
to	O
use	O
the	O
DLR	O
for	O
the	O
upcoming	O
Visual	B-Language
Basic	I-Language
2010	O
(	O
VB	O
10.0	O
)	O
and	O
Managed	B-Language
JScript	I-Language
(	O
ECMAScript	B-Language
3.0	O
)	O
.	O
</s>
<s>
However	O
,	O
as	O
of	O
August	O
2009	O
,	O
Microsoft	O
has	O
no	O
more	O
plans	O
to	O
implement	O
Managed	B-Language
JScript	I-Language
on	O
the	O
DLR	O
.	O
</s>
<s>
Like	O
C#	B-Application
,	O
Visual	B-Language
Basic	I-Language
can	O
access	O
objects	O
from	O
dynamic	B-Language
languages	I-Language
built	O
on	O
the	O
DLR	O
such	O
as	O
IronPython	B-Application
and	O
IronRuby	B-Language
.	O
</s>
<s>
PowerShell	B-Application
3.0	O
,	O
released	O
in	O
Windows	B-Application
8	I-Application
,	O
was	O
updated	O
to	O
use	O
the	O
DLR	O
.	O
</s>
<s>
IronScheme	B-Language
,	O
a	O
Scheme	B-Language
implementation	O
,	O
was	O
planning	O
to	O
build	O
upon	O
the	O
DLR	O
.	O
</s>
<s>
This	O
idea	O
was	O
abandoned	O
because	O
the	O
DLR	O
branch	B-General_Concept
used	O
by	O
the	O
project	O
became	O
out	O
of	O
sync	O
with	O
the	O
trunk	B-General_Concept
,	O
and	O
also	O
because	O
(	O
according	O
to	O
the	O
project	O
coordinator	O
)	O
the	O
current	O
version	O
of	O
the	O
DLR	O
at	O
that	O
time	O
could	O
not	O
support	O
the	O
majority	O
of	O
Scheme	B-Language
's	O
requirements	O
.	O
</s>
<s>
The	O
Dynamic	B-Application
Language	I-Application
Runtime	I-Application
is	O
built	O
on	O
the	O
idea	O
that	O
it	O
is	O
possible	O
to	O
implement	O
language	O
specificities	O
on	O
top	O
of	O
a	O
generic	O
language-agnostic	B-Language
abstract	B-Data_Structure
syntax	I-Data_Structure
tree	I-Data_Structure
,	O
whose	O
nodes	O
correspond	O
to	O
a	O
specific	O
functionality	O
that	O
is	O
common	O
to	O
many	O
dynamic	B-Language
languages	I-Language
.	O
</s>
<s>
The	O
compiler	O
for	O
any	O
dynamic	B-Language
language	I-Language
implemented	O
on	O
top	O
of	O
the	O
DLR	O
has	O
to	O
generate	O
DLR	O
abstract	O
trees	O
,	O
and	O
hand	O
it	O
over	O
to	O
the	O
DLR	O
libraries	O
.	O
</s>
<s>
Since	O
the	O
type	O
of	O
an	O
object	O
—	O
as	O
well	O
as	O
the	O
members	O
it	O
contains	O
—	O
in	O
dynamic	B-Language
languages	I-Language
can	O
change	O
during	O
a	O
program	O
lifetime	O
,	O
a	O
method	O
invocation	O
must	O
check	O
the	O
method	O
list	O
to	O
see	O
if	O
the	O
invocation	O
is	O
a	O
valid	O
one	O
.	O
</s>
<s>
In	O
contrast	O
to	O
other	O
efforts	O
like	O
the	O
Parrot	B-Language
virtual	I-Language
machine	I-Language
(	O
with	O
no	O
dependencies	O
)	O
or	O
Da	B-Application
Vinci	I-Application
Machine	I-Application
(	O
built	O
on	O
Java	O
's	O
JVM	B-Language
by	O
adding	O
new	O
bytecodes	O
in	O
the	O
JVM	B-Language
instruction	I-Language
set	I-Language
)	O
,	O
the	O
DLR	O
is	O
built	O
on	O
top	O
of	O
the	O
existing	O
Common	O
Language	O
Runtime	O
,	O
the	O
.NET	B-Application
Framework	I-Application
virtual	O
machine	O
.	O
</s>
