At 8:22 AM -0600 10/31/97, Bob Hovde wrote:
>Randy,
>
>I agree that we should be able to agree on representations of units
>(although there will probably not be universal agreement on who controls
>those representations).  What about the next step?  If I were to calculate
>latitude of a moving target by integrating north velocity, I probably would
>assume the velocity was constant over the integration step.  As JADS
>discovered in their Linked Simulators Phase test, the assumption is invalid
>for maneuvering targets, and can cause divergence of calculated position
>between different simulations.

I think there is a big difference between data standards and
representational fidelity.  Data standards tell you what the
data means.  If you must combine it with assumptions to get
what you want, the assumptions also need to be agreed.  In
DIS there were 10 different "dead-reckoning algorithms",
actually position extrapolation assumption sets.  A data item
told you which one to use to consistently extrapolate the
standardized position data.  If you did something else, you
were wrong.

As far as "universal agreement", that is something built into
the SISO standards processes.  If you are concerned about your
position being reflected in the agreed-to representation, you
need to be involved in the SDG doing the standardization.

>
>DoD has said that the goal for M&S is to have each acquisition program
>develop a model early in development that can be upgraded and used
>throughout its life (I didn't say you had to believe it would happen), up
>to and including T&E and training after fielding.  How do the user
>communities (RDE, T&E, etc.) establish their non-unit requirements?  Do we
>have to depend on everyone reading every test report, do we need a "lessons
>learned," a "best practices," or do we just depend on contractors being
>smart enough to know all of the mistakes that have been made in the past?
>Some of this is probably outside of the SIW charter, but is related to
>acceptance of simulations for such things as T&E.  It also is related to
>being able to take two legacy simulations and decide if they can provide
>useful information when linked together in a federation.

Well, I agree that finding all the "community knowledge" is an
ongoing outreach challenge.  One of the important parts of the
SISO Vision is to produce opportunities, the SIW and Standards,
for people to contribute what they know.  I accept that building
a watering hole is not the same as dragging all the horses to it.
I expect DoD policy to give all the horses a clear mandate to
use the CMMS/HLA/DS products.

>
>Bob
>
>At 04:26 PM 10/30/97 -0500, you wrote:
>>Bob,
>>
>>   The DoD Common Technical Framework consists of three things:
>>1) the Conceptual Model of the Mission Space (CMMS); 2) the HLA;
>>and 3) Data Standards.  These three things are a lot more useful
>>together than they are separately.  HLA will be a lot more handy
>>when your HLA-stuff (ie. SOMs, FOMs, RTIs, and cool tools) work
>>with a database of standard datums.  If there is a standard way
>>to represent speed, and you can swipe it easier than cook up
>>your own, then everybody who represents speed that way will have
>>higher utility (karma?) than the bad boys who represent it oddly.
>>Some things may have several standard representations, position
>>is the most widely used example.  If you use one datum standard,
>>let's call it UTM/AMSL_position, and you want to go into a
>>federation what has agreed on DIS_GeoC_position, then you might
>>need a translator.  With any luck, those translations between
>>equivalent standard datums will be standardized themselves.  But
>>at least you know unambigously what you need to do.  This is a
>>huge step forward from where you were before HLA.  Right today
>>the Data Standards work isn't done, and so you aren't seeing
>>that synergy.  But I expect you'll see Data Standards effort
>>products within the next 6 months that will make a big improvement
>>in your standard of living.  I just can't go along with your
>>comment that "no-one had a good answer", Roy Scrudder and his
>>UTA team are specifically working on just such an answer.
>>
>>/Randy
>>
>>At 4:18 PM -0600 10/29/97, Bob Hovde wrote:
>>>The request as refined below brings up the more general question of
>>>conventions.  Is there anywhere in the simulation world a set of
>>>conventions for units, signs, etc., or does each simulation have to come up
>>>with a translator interface to the rest of the world?  This question came
>>>up in the T&E Forum at the last SIW, and no-one had a good answer.  In even
>>>more general terms, how can a user community put its unique requirements
>>>before the other communities that MIGHT have to work with them someday?
>>>
>>>Bob Hovde
>>>
>>>At 07:57 AM 10/29/97 +0000, you wrote:
>>>>Let me refine my request a little.  I had earlier asked about
>>>>reference FOMs to design a SOM to be compatible with.  What I had in
>>>>mind was not, should my missile simulation publish attributes for one
>>>>missile or for several (this is governed by the simulation
>>>>architecture, which for legacy systems is already in place), but what
>>>>sort of sign conventions and units I should be using.  Publishing my
>>>>position in downrange/crossrange/altitudeAGL is just as general as
>>>>publishing it in latitude/longitude/altitudeMSL but is different.
>>>>Similarly, publishing canard deflection angles in degrees is as
>>>>general is publishing them in radians, but is different.  The
>>>>question is not one of simulation generality but rather one of
>>>>sign conventions, zero conventions, and systems of units.  I have
>>>>found that the RPR-FOM publishes its positions in meters, but it
>>>>doesn't address the sign or zero conventions.  At least, not yet.
>>>>
>>>>I am not talking about HLA compliance.  I am talking about being
>>>>useful.
>>>>[snip]
>>
>>/Randy Saunders
>>Hughes Training Inc.
>>(248) 619-8321
>>[log in to unmask]
>>
>>
>>
>>
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/Randy Saunders
Hughes Training Inc.
(248) 619-8321
[log in to unmask]






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