Ada and the DoD HLA (was: Once again, Ada absent from DoD SBIR solicitation)

[John Cosby <John.D.Cosby@cpmx.saic.com>]

Stanley R. Allen wrote:
> My company's job is building big simulators, and the
> new DoD *mandate* (sound familiar?) for simulations is
> called HLA (High Level Architecture), which is being
> developed by the Defense Modeling and Simulation
> Office (DMSO)  See http://www.dmso.mil/projects/hla/
> for some interesting overview and mandate stuff.

This is a mandate with teeth - HLA compliance is specified
in the contracts being proposed and awarded now, and has been 
back-filled into existing developments.  Unlike the Ada mandate, 
which isn't often specified in the contract, or lets folks weasle out.

> It's a good idea. It's time has come.  But the first
> cut of the HLA API is given in .... C++ !  No mention
> of Ada anywhere.  No justification is given for
> avoiding the Ada madate.  And HLA is a *big* *deal*.
> All the major DoD simulator contractors are hankering
> after this work.

First, it's not the HLA API - it's the first implementation 
of the HLA Runtime Infrastructure that's being written in
C++.  The original design was to use CORBA IDL to specify
the interfaces, allowing any language for which an emitter
exists to be used.  The prototype versions of the RTI,
up to and including RTI 1.0, are being developed by the
gov't (MITRE and MIT Lincoln Labs) in C++.  The gov't is
supposed to solicit commercial development of one or more
RTIs Real Soon Now - the prototype should be all grown up
around February.

You want mention of Ada?  DMSO funded several efforts to use
the  prototype RTI and get feedback from different groups of
simulation users.  Originally (and this is buried in the
AMG minutes on the web site),  there was to have been an
Ada front-end, but the RTI developers had so much trouble
with the initial prototype releases they couldn't support
a parallel effort.  We (I worked one of the "proto-federation"
efforts) had to interface our Ada simulation system to the
C++ interfaces generated from the IDL interface specification.  
Why didn't we just use the Ada95 CORBA IDL emitter for
our ORB?  It didn't exist yet; it came along about the
time the protofederation effort ended.  Believe me, there's
been talk about Ada - not too productive, but the issue's
never been killed.

> So, two DoD mandates mitigate against one another.
> (Homework: ask yourself seriously which one will win.)
> Note that HLA-compliance for simulators must be
> considered new development; there is no such thing
> as a COTS HLA-based system.  It's too new.  So, the
> COTS excuse is no reason.

Um... actually, the "commercial RTI" may be considered COTS
eventually, or GOTS.  DMSO _really_ doesn't want every
simulation effort writing their own RTI - that would make
interoperability a problem - they want everyone using a "standard" 
RTI.  (Unlike the old DIS and ALSP standards, HLA specifies object
models
and leaves it to the RTI to sweat the bit-formats going out over the
network - there's no way to guarantee interoperability of two "HLA
compliant" simulations using different RTIs).  If the RTI's in C++, this
could indeed be a problem - I learned a lot of hard lessons about making
C++ callable from Ada over the last six months.

And yes, I'm very nervous about using an RTI written in C++.
Can't you tell?

<snippage>
 
> If you believe in the promise of Ada (as I do), you
> could do yourself a favor by listening to Gregory
> Aharonian.  And then doing something about it.

I am.  Sometime in November, I get to start giving feedback
to the Ada interface specification that should be published with
the RTI 1.0 release; I also get to go to work in Nov./Dec. porting 
the RTI to the IBM RS/6000 platform, hopefully with an Ada95 front-end.
Anyway, that's the plan.  Check with me in December and I'll let
you know how it's going.

John
-- 
John Cosby                 | Opinions expressed are those of the
individual
SAIC Orlando               | and in no way represent any official
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John.D.Cosby@cpmx.saic.com |  or opinion of SAIC unless specifically
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(407) 282-6700 x216        |          Live long and perspire....