TENA
Test and Training Enabling
Architecture
TENA
• TENA is used in range environments, often in
the L portion of LVC
• Slightly different emphasis; small devices, realtime-ish, sometimes embedded, high
performance in the sense of low overhead
required, multiple unusual platforms
• Government-owned source built for multiple
platforms
Live, Virtual, constructive
TENA
• Large-ish user support network
• https://www.tena-sda.org
• Available to international militaries with
permission (used in Sweden)
Remote Objects
• There’s a popular concept in computer science
called “remote procedure calls” or “distributed
objects.” You’ve got a piece of code on one host,
and you want to call it from another
• You can create and send a message from the
client to the server to make this call happen, but
it’s popular to make it appear as if the object is
“really” on the client. This is done via a proxy
object
Proxy Objects
Proxy
-doSomething(int i)
-doSomethingElse(float f);
Real Object
-doSomething(int i)
-doSomethingElse(float f);
The proxy is a “stand-in” for the real object on another host. Methods are called by
a user on the proxy, which does no computation itself. Instead, it passes the request
(along with any parameters) to the real object on a server. The server does the
computation and passes back the return value
Proxy and Servant
• The object on the client side is called the proxy, while the
“real” object on the server side is called the servant
• This means the proxy and servant need to agree on how
messages are passed back and forth, ports for passing
messages over sockets, etc. The good news is that this can
be automated by appropriate code, so the user doesn’t
have to write any of it
• Typically you write a interface file in a special language,
then the proxy code and servant interface is generated for
you
• The infrastructure can use a variety of technologies for
message passing: multicast, tcp, udp, etc.
TENA Description Language
The TDL/CORBA IDL below is run through a compiler to generate the proxy
objects and to create the server-side connectors. (TDL and IDL are very similar)
TAO CORBA Architecture
Dangers
• While this is nice, always remember that the
proxy object is not the same thing as the real
object. Calls are being made across the
network, so they’ll be much slower and less
reliable than using a “real” object
for(int idx = 0; idx < 1000; idx++
{
proxy.doSomething(idx);
}
TENA Remote Objects
• Remote objects are the approach that TENA
takes
• Clients have proxies that connect to the
servant objects running on other hosts, so we
may have a radar object instance running on a
device on the range being called from a host
in the lab, and the radar object being shown in
a DIS application via a gateway
Stateful Distributed Objects
• TENA adds “stateful distributed objects” to
regular distributed objects
• With distributed objects you need to call a
method to discover state
• With SDOs the state is pushed to subscribed
listeners periodically (often at state change
points)
• So for example a Radar object instance might tell
listening objects that it has turned on rather than
waiting for other objects to ask its state, or
having other objects poll its state
TENA
• So a TENA application can consist of
– Objects that that application publishes (for
example, a radar or tank)
– Objects that that application is listening to (for
example, helicopters published by other
applications)
– Your own application logic
• TENA has gateways to allow operation with
other standards, for example DIS or HLA
TENA
• TENA uses something called CORBA in the
background, specifically the TAO realtime
CORBA ORB
• But all this is hidden from the user, and as a
result is never seen directly
• Multiple language bindings: C++ is primary, C#
also, Java in beta
CORBA
• CORBA provides the infrastructure for many
things:
– Publishing objects
– Handling parameter serialization, object serialization,
response serialization
– Object lookup
– The interface description language (IDL)
– Generating proxy and servant interfaces
• You provide the servant logic, CORBA does most
of the rest
Object Serialization
• What if you pass an object as a parameter to a
method on a servant? Eg, Position with
attributes of floats (x,y,z). Or what if you want
an object returned as a method result?
• The attributes of the object need to be placed
in a format that can be passed in a message to
the servant; this is all done automatically, but
it needs to be done
• How to you find published objects?
TENA
TENA App
Cooperating TENA Apps
Overall
• TENA uses a hidden implementation of CORBA
• Adds “stateful distributed objects”, which
pushes state information to subscribed
listeners
• High performance, hides most network details
• Gov’t-provided middleware for most
architectures (Linux/Windows/IOS/32/64)