<s>
Distributed	B-Operating_System
Interactive	I-Operating_System
Simulation	I-Operating_System
(	O
DIS	O
)	O
is	O
an	O
IEEE	O
standard	O
for	O
conducting	O
real-time	O
platform-level	O
wargaming	O
across	O
multiple	O
host	O
computers	O
and	O
is	O
used	O
worldwide	O
,	O
especially	O
by	O
military	O
organizations	O
but	O
also	O
by	O
other	O
agencies	O
such	O
as	O
those	O
involved	O
in	O
space	O
exploration	O
and	O
medicine	O
.	O
</s>
<s>
The	O
standard	O
itself	O
is	O
very	O
closely	O
patterned	O
after	O
the	O
original	O
SIMNET	B-General_Concept
distributed	B-Operating_System
interactive	I-Operating_System
simulation	I-Operating_System
protocol	O
,	O
developed	O
by	O
Bolt	O
,	O
Beranek	O
and	O
Newman	O
(	O
BBN	O
)	O
for	O
Defense	O
Advanced	O
Research	O
Project	O
Agency	O
(	O
DARPA	O
)	O
in	O
the	O
early	O
through	O
late	O
1980s	O
.	O
</s>
<s>
In	O
the	O
early	O
1990s	O
,	O
IST	O
was	O
contracted	O
by	O
the	O
United	O
States	O
Defense	O
Advanced	O
Research	O
Project	O
Agency	O
to	O
undertake	O
research	O
in	O
support	O
of	O
the	O
US	O
Army	O
Simulator	O
Network	O
(	O
SimNet	B-General_Concept
)	O
program	O
.	O
</s>
<s>
Funding	O
and	O
research	O
interest	O
for	O
DIS	O
standards	O
development	O
decreased	O
following	O
the	O
proposal	O
and	O
promulgation	O
of	O
its	O
successor	O
,	O
the	O
High	B-Operating_System
Level	I-Operating_System
Architecture	I-Operating_System
(	O
simulation	O
)	O
(	O
HLA	O
)	O
in	O
1996	O
.	O
</s>
<s>
HLA	O
was	O
produced	O
by	O
the	O
merger	O
of	O
the	O
DIS	O
protocol	O
with	O
the	O
Aggregate	B-Operating_System
Level	I-Operating_System
Simulation	I-Operating_System
Protocol	I-Operating_System
(	O
ALSP	B-Operating_System
)	O
designed	O
by	O
MITRE	O
.	O
</s>
<s>
There	O
was	O
a	O
NATO	O
standardisation	O
agreement	O
(	O
STANAG	B-Operating_System
4482	I-Operating_System
,	O
Standardised	O
Information	O
Technology	O
Protocols	O
for	O
Distributed	B-Operating_System
Interactive	I-Operating_System
Simulation	I-Operating_System
(	O
DIS	O
)	O
,	O
adopted	O
in	O
1995	O
)	O
on	O
DIS	O
for	O
modelling	O
and	O
simulation	O
interoperability	O
.	O
</s>
<s>
Simulation	O
state	O
information	O
is	O
encoded	O
in	O
formatted	O
messages	O
,	O
known	O
as	O
protocol	B-Protocol
data	I-Protocol
units	I-Protocol
(	O
PDUs	O
)	O
and	O
exchanged	O
between	O
hosts	O
using	O
existing	O
transport	B-Architecture
layer	I-Architecture
protocols	O
,	O
including	O
multicast	O
,	O
though	O
broadcast	O
User	B-Protocol
Datagram	I-Protocol
Protocol	I-Protocol
is	O
also	O
supported	O
.	O
</s>
<s>
The	O
RPR	B-Operating_System
FOM	I-Operating_System
is	O
a	O
Federation	O
Object	O
Model	O
(	O
FOM	O
)	O
for	O
the	O
High-Level	B-Operating_System
Architecture	I-Operating_System
designed	O
to	O
organize	O
the	O
PDUs	O
of	O
DIS	O
into	O
an	O
HLA	O
object	O
class	O
and	O
interaction	O
class	O
hierarchy	O
.	O
</s>
<s>
The	O
purpose	O
is	O
to	O
support	O
transition	O
of	O
legacy	O
DIS	O
systems	O
to	O
the	O
HLA	O
,	O
to	O
enhance	O
a	O
priori	O
interoperability	O
among	O
RPR	B-Operating_System
FOM	I-Operating_System
users	O
and	O
to	O
support	O
newly	O
developed	O
federates	O
with	O
similar	O
requirements	O
.	O
</s>
<s>
The	O
most	O
recent	O
version	O
is	O
RPR	B-Operating_System
FOM	I-Operating_System
version	O
2.0	O
that	O
corresponds	O
to	O
DIS	O
version	O
6	O
.	O
</s>
