1. Chapter16 Methodology: How to Model and Simulate

2. M&S Methodology
First think about your objectives- find a level of difficulty that seems achievable in the time available.
Develop the experimental frames first to meet these objectives.
Develop your atomic models and coupled models and and test them in hierarchical stage wise fashion in SimView.
Start your exploratory phase -- get some preliminary results of execution within experimental frames. What is the “lay of the land”? Which factors appear to matter most?
Start your production runs (for final results) by concentrating on the factors that seem to be important from your initial exploration.
If you need better performance, remove all unessential code, including output and print statements. Switch execution from SimView to fast-as-can simulation as shown next.
For greater performance migrate your model to parallel/distributed fast-as-can simulation (not currently available).
If your objectives were to develop real-time execution models, migrate them to real-time execution (distributed, non-distributed) as shown next.

3. Suggested Project Report Outline
Problem statement – Objectives of the Project
General Description of the System to be Studied
Objectives of the Modeling and Simulation Study
The Simulation Model
System Entity Structure or Hierarchical diagrams and
explanation of operation
Illustrative DEVSJAVA code or pseudo code
Experimental frame and how it serves to achieve the Objectives
Experiments
Results ( or expected results)
Conclusions (what did you learn from this work
Future Work
References
Appendix: more details or code

4. Categorizing Simulation Modes and Packages in DEVSJAVA
Non Distributed
Distributed
Real-time
SimView supports visual behavior validation. Using real-time simulation on a single workstation allows checking timing. Tunable real-time coordinator used by SimView allows speed as well.
Packages:
genDevs.modeling
genDevs.simulation
simView
genDevs.simulation.realtime
Only decentralized is currently available for distribution. Centralized available upon requirest.
genDevs.simulation..distributed
Fast-as-can
Not available currently for distribution.
Available upon requirest.
centralized
Decentralized
Atomic
federate
Coupled
Federate
Non threaded
threaded

5. Model Development using Model Continuity
Implementation/
Logical
Simulation
Model
Distribution/
Distributed
Simulation
Real-Time
Distributed
Simulation/
Execution
Modeling
Checks Model
Logical Behavior
Checks Model
Logical Behavior
in Distributed
Environment
Checks Model
Temporal
Behavior
DEVS
Formalism
genDevs.
simulation.
distributed
genDevs.
simulation.
realTime
genDevs.
simulation

6. Using inheritance and polymorphism to allow easy switching from structure/behavior viewing to fast simulation
atomic
digraph
atomicSimulator
coupledSimulator
coordinator
Viewable
Atomic
Digraph
ViewableAtomic
Simulator
coupledRTSimulator
SimView
Coordinator
Later, when ready for production runs, execute them without change in fast-as-can simulation
Even though ViewableAtomic and ViewableDigraph models
can hold information intended for SimView, they need not
be altered to run outside of SimView. For example, to run
a ViewableDigraph model in a main routine define:
public static void main(String args[]){
ViewableDigraph d = new (Random,rule30CellSpace):
r = new coordinator (d);
r.initialize();
//to measure execution time if desired:
initTime = System.currentTimeMillis();
r.simulate(100);
termTime = System.currentTimeMillis();}
This can be executed in JBuilder of by changing directory to DevsJava/classes and entering on the command line –
>java Random.rule30CellSpace
You can develop models and test them in SimView
simView.
ViewableDigraph
To understand how this is possible, consider that in atomicSimulator the Devs Simulator Cycle implementation includes “hooks” within its methods, e.g.,
public void computeInputOutput(double t){
if(equalTN(t)) { output = myModel.Out();}
else{output = new message();}
computeInputOutputHook1() ;}
These hooks are dummy methods within atomicSimulator, e.g.,
protected void computeInputOutputHook1() {}
In ViableAtomicSimulator the hooks are given definitions
that allow the SimViewCoordinator to get the infromation
it needs to display in SimView, .e.g.,
protected void computeInputOutputHook1(){
if (listener == null) return;
ContentIteratorInterface iterator = output.mIterator();
while (iterator.hasNext()) {
ContentInterface content = iterator.next();
listener.contentOutputted((content)content,\
viewableAtomic, content.getPort().getName()); } }
simView.
ViewableAyatomic

7. Using toString() and toObject() to facilitate deploying models in distributed simulation
receiver
sender
DEVS simulator uses toString() to encode the entity as a String which is sent across the wire
public message out( ){
message m = new message();
m.add(makeContent("out",
new vect2DEnt(x,y)));
return m; }
public void deltext(double e ,message x){
for (int i=0; i< x.getLength();i++)
if (messageOnPort(x,“in",i)) {
entity en = x.getValOnPort(“in",i);
position = vect2DEnt.toObject(en); }
The modeler must define toString() for the simulator to use polymorphically. For example:
public String toString(){
return doubleFormat.niceDouble( x ) +
","+doubleFormat.niceDouble(y); }
public String getName(){
return toString();
The modeler also needs to define toObject() and use this method in decoding the message.
public static vect2DEnt toObject(String nm){
int commaIndex = nm.indexOf(",");
String xs = nm.substring(0,commaIndex);
String ys = nm.substring(commaIndex+1,nm.length());
return new vect2DEnt(Double.parseDouble(xs),Double.parseDouble(ys)); }
public static vect2DEnt toObject(entity ent){
return toObject(ent.getName());

8. Deploying a coupled model onto a distributed, decentralized, real-time simulation
For the coupled model define a RTCoordinatorServer,e.g.,:
public class StartVehicleSpaceServer{
public static void main(String[] args) {
try{
System.out.println("For use by clients, this host is " +InetAddress.getLocalHost().getHostAddress());
}catch(Exception c){}
new RTCoordinatorServer(new vehicleSpace(), 10);}
You can develop models and test them in SimView
This will give you the address needed by clients
For each component model define a RTCoordinatorClient, e.g.,:
public class StartEvaderClient{
public static void main(String[] args) {
new RTCoordinatorClient(
new vehicle("evader",new vect2DEnt(40,40)),
" ", //RTCoordinatorServer’s address //or if on same machine as the server
//you can use "localhost",
Constants.serverPortNumber); }}
StartVehicleSpaceServer
StartEvader
Client
StartPursuer
Client
Continuity.
StartVehicleSpaceServer
intranet or internet
Later, when ready for production runs, execute them without change in distributed, real0time, decentralized
simulation
You can now distribute these classes onto one or more
computers and execute them from jBuilder or from the
command line as illustrated before.
You can also distribute hierarchically using RTCoordinatorServerAndClient

9. V&V

10. General System Philosophy
George Klir, “Architecture of General Systems”

11. Modeling & Simulation/Systems Theory
Mathematical
Systems
Theory
Hierarchy of
System
Specifications
Framework for
Modeling and
Simulation
Specification
Morphisms
entities
relations
uses the formalism of
is interpreted by

12. M&S Framework DEVS HLA/SOA Layered architecture Collaboration Decision
Objectives represented by
Model
Real World
Simulator
modeling
relation
simulation
Experimental Frame
Network
Simulation
Modeling
Search
Decision
Collaboration
DEVS
HLA/SOA
Layered architecture
Entities formalized as systems; relations as system morphisms

13. DEVS Modeling & Simulation Framework
DEVS = Discrete Event System Specification
Provides sound M&S framework
Derived from Mathematical dynamical system theory
Supports hierarchical, modular composition and reuse
Can express Discrete Time, Continuous and hybrid models
Event-orientation enables efficient simulation
HLA/SOA enables interoperability of existing simulations
DEVS supports developing new simulation models within an object-oriented computational framework

14. JM Application: C4ISR System-of-System Design
Joint MEASURETM
Jointly Developed by Lockheed and UA under DARPA ASTT
Mission Effectiveness Simulator for
System-of-Systems
employs moderate level of resolution
Inter-satellite
Communication
Network
Simulation
Modeling
Search
Decision
Collaboration
HLA
DEVS ME
Threat
Detection
Data
JM Application: C4ISR System-of-System Design
Relay
Threat
Analysis
WAN link
* Mission Effectiveness Analysis Simulator for Utility, Research and Evaluation

15. Hierarchy of System Specifications and Morphisms
simulation model construction
at high levels
System
specification
levels
Morphisms
at each level
V&V loop
structure to
behavior
behavior to
structure
experimental
testing at low levels

16. V&V