<s>
Microsoft	B-Operating_System
Transaction	I-Operating_System
Server	I-Operating_System
(	O
MTS	O
)	O
was	O
software	O
that	O
provided	O
services	O
to	O
Component	B-Application
Object	I-Application
Model	I-Application
(	O
COM	B-Application
)	O
software	B-Architecture
components	I-Architecture
,	O
to	O
make	O
it	O
easier	O
to	O
create	O
large	O
distributed	O
applications	O
.	O
</s>
<s>
The	O
major	O
services	O
provided	O
by	O
MTS	O
were	O
automated	O
transaction	B-General_Concept
management	O
,	O
instance	O
management	O
(	O
or	O
just-in-time	O
activation	O
)	O
and	O
role-based	O
security	O
.	O
</s>
<s>
MTS	O
is	O
considered	O
to	O
be	O
the	O
first	O
major	O
software	O
to	O
implement	O
aspect-oriented	B-Architecture
programming	I-Architecture
.	O
</s>
<s>
MTS	O
was	O
first	O
offered	O
in	O
the	O
Windows	B-Device
NT	I-Device
4.0	O
Option	O
Pack	O
.	O
</s>
<s>
In	O
Windows	B-Application
2000	I-Application
,	O
MTS	O
was	O
enhanced	O
and	O
better	O
integrated	O
with	O
the	O
operating	O
system	O
and	O
COM	B-Application
,	O
and	O
was	O
renamed	O
COM+	O
.	O
</s>
<s>
COM+	O
added	O
object	O
pooling	O
,	O
loosely-coupled	B-Application
events	I-Application
and	O
user-defined	O
simple	O
transactions	O
(	O
compensating	O
resource	O
managers	O
)	O
to	O
the	O
features	O
of	O
MTS	O
.	O
</s>
<s>
COM+	O
is	O
still	O
provided	O
with	O
Windows	B-Application
Server	I-Application
2003	I-Application
and	O
Windows	B-Device
Server	I-Device
2008	I-Device
,	O
and	O
the	O
Microsoft	B-Application
.NET	I-Application
Framework	I-Application
provides	O
a	O
wrapper	O
for	O
COM+	O
in	O
the	O
EnterpriseServices	O
namespace	O
.	O
</s>
<s>
The	O
Windows	B-Application
Communication	I-Application
Foundation	I-Application
(	O
WCF	O
)	O
provides	O
a	O
way	O
of	O
calling	O
COM+	O
applications	O
with	O
web	O
services	O
.	O
</s>
<s>
However	O
,	O
COM+	O
is	O
based	O
on	O
COM	B-Application
,	O
and	O
Microsoft	O
's	O
strategic	O
software	O
architecture	O
is	O
now	O
web	O
services	O
and	O
.NET	B-Application
,	O
not	O
COM	B-Application
.	O
</s>
<s>
There	O
are	O
pure	O
.NET-based	O
alternatives	O
for	O
many	O
of	O
the	O
features	O
provided	O
by	O
COM+	O
,	O
and	O
in	O
the	O
long	O
term	O
it	O
is	O
likely	O
COM+	O
will	O
be	O
phased	O
out	O
.	O
</s>
<s>
COM	B-Application
components	O
that	O
run	O
under	O
the	O
control	O
of	O
the	O
MTS	O
Executive	O
are	O
called	O
MTS	O
components	O
.	O
</s>
<s>
In	O
COM+	O
,	O
they	O
are	O
referred	O
to	O
as	O
COM+	O
Applications	O
.	O
</s>
<s>
As	O
with	O
other	O
COM	B-Application
components	O
,	O
an	O
object	O
implementing	O
the	O
IClassFactory	O
interface	B-Application
serves	O
as	O
a	O
Factory	B-Application
Object	I-Application
to	O
create	O
new	O
instances	O
of	O
these	O
components	O
.	O
</s>
<s>
MTS	O
inserts	O
a	O
Factory	B-Application
Wrapper	O
Object	O
and	O
an	O
Object	O
Wrapper	O
between	O
the	O
actual	O
MTS	O
object	O
and	O
its	O
client	O
.	O
</s>
<s>
Whenever	O
the	O
client	O
makes	O
a	O
call	O
to	O
the	O
MTS	O
component	O
,	O
the	O
wrappers	O
(	O
Factory	B-Application
and	O
Object	O
)	O
intercept	O
the	O
call	O
and	O
inject	O
their	O
own	O
instance-management	O
algorithm	O
called	O
the	O
Just-In-Time	O
Activation	O
(	O
JITA	O
)	O
into	O
the	O
call	O
.	O
</s>
<s>
In	O
addition	O
,	O
based	O
on	O
the	O
information	O
from	O
the	O
component	O
's	O
deployment	O
properties	O
,	O
transaction	B-General_Concept
logic	O
and	O
security	O
checks	O
also	O
take	O
place	O
in	O
these	O
wrapper	O
objects	O
.	O
</s>
<s>
For	O
every	O
MTS-hosted	O
object	O
,	O
there	O
also	O
exists	O
a	O
Context	O
Object	O
,	O
which	O
implements	O
the	O
IObjectContext	O
interface	B-Application
.	O
</s>
<s>
Methods	B-Language
in	O
the	O
MTS	O
component	O
call	O
into	O
the	O
Context	O
Object	O
through	O
its	O
IObjectContext	O
interface	B-Application
.	O
</s>
<s>
And	O
when	O
the	O
request	O
is	O
serviced	O
and	O
the	O
reply	O
is	O
sent	O
back	O
to	O
the	O
client	O
,	O
the	O
component	O
either	O
calls	O
SetComplete( )	O
/SetAbort	O
(	O
)	O
,	O
or	O
its	O
transaction	B-General_Concept
ends	O
,	O
or	O
the	O
client	O
calls	O
Release( )	O
on	O
the	O
reference	O
to	O
the	O
object	O
,	O
and	O
the	O
actual	O
MTS	O
object	O
is	O
destroyed	O
.	O
</s>
<s>
vote	O
on	O
the	O
result	O
of	O
the	O
transaction	B-General_Concept
.	O
</s>
<s>
It	O
is	O
thus	O
possible	O
to	O
implement	O
high-latency	O
resources	O
as	O
asynchronous	O
resource	O
pools	O
,	O
which	O
should	O
take	O
advantage	O
of	O
the	O
stateless	O
JIT	O
activation	O
afforded	O
by	O
the	O
middleware	B-General_Concept
server	O
.	O
</s>
