Conference presentation, SIMUTOOLS 2008, Nice, France. Please visit https://sites.google.com/site/simulationarchitecture/ for further information

1. March 3-7, 2008
Marseille, France
A Layered Architecture for the
Model-driven Development of
Distributed Simulators
Daniele Gianni* Andrea D’Ambrogio# Giuseppe Iazeolla#
(*) Dept. of Electrical & Electronic Eng. (#) Dept. of Computer Science
Imperial College London University of Roma “Tor Vergata”
London (UK) Roma (Italy)

2. Overview
 Motivations
 Definition of SimArch
• Layers, Service Interfaces and Data Interfaces
 Example implementation of a SimArch-based
simulation language
• jEQN
 Application to the model-driven development
of a distributed simulator
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3. Motivations
 The development of distributed simulators generally
requires more effort and know-how compared to
centralized (local) simulators
 Only reusability and interoperability aspects have been
addressed by distributed simulation approaches
 Adaptability aspects (how to switch from local to
distributed simulation) have not been addressed
 The proposed layered architecture exploits model-driven
development to allow the simulation developer to
abstract from the execution environment and to deal
only with the definition of the hi-level simulation model
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4. SimArch
 A layered architecture to enable the model-
driven development of distributed simulators:
• transparent deployment of simulation
components in either a local or a distributed
environment
• transparent introduction/modification of the
layers’ implementation to meet additional/specific
requirements
• definition of custom (domain-specific) simulation
languages on top of the layered architecture
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5. SimArch Main Characteristics
 Based on the process interaction paradigm
 Composed of four layers
 Based on the definition of:
• Service interfaces
• Data interfaces
• Factory interfaces for component instantiation
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6. Process Interaction Paradigm
ev2
Key
E2
ev1
Entity
E1 Input Port
ev3 Output Port
E3
Link/Event ev
ev4
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7. Simulation Model Layer Layer 4
Simulation Components
Layer 3
Layer
Discrete Event Simulation
Service Layer Layer 2
SimArch Distributed Discrete
Event Simulation Layer Layer 1
Layers Distributed Computing
Infrastructure Layer 0
CORBA
DIS
Grid WS HLA
General Purpose
Simulation Oriented
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8. SimArch Service Interfaces
(layers 12)
«interface»
Layer2ToLayer1
+initDistributedSimulationInfrastructure()
+postProcessingDistributedSimulationInfrastructure()
+sendEvent(in event : Event)
+waitNextDistributedEvent()
+waitNextDistributedEventBeforeTime(in time : Time)
«interface»
Layer1ToLayer2
+scheduleEvent(in event : Event)
+scheduleSimulationEndEvent(in time : Time)
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9. SimArch Service Interfaces
(layers 23)
«interface» «interface»
Layer3ToLayer2 Layer2ToLayer3
+getUserInterface() : Layer3toLayer2UserInterface
+body()
+getDeveloperInterface() : Layer3ToLayer2DeveloperInterface
+getId() : Integer
+getEntityName() : Name
+printStatistics()
+setEventReceived()
+setReceivedEvent(in event : Event)
+setId(in id : Integer)
+setSystemName(in name : Name)
«interface» «interface»
Layer3toLayer2UserInterface Layer3ToLayer2DeveloperInterface
+registerEntity(in entity : GeneralEntity) +getClock() : Time
+start() +waitNextEvent()
+hold(in time : Time)
+holdUnlessIncomingEvent(in time : Time) : Boolean
+send(in entity : Entity, in delay : Time, in tag : Enum, in data : Object)
+send(in port : OutputPort, in delay : Time, in tag : Enum, in data : Object)
+send(in recipient : Name, in delay : Time, in tag : Enum, in data : Object)
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10. SimArch Data Interfaces (1/2)
«interface»
Link
+getInputPorts() : List of InputPort
+getOutputPorts() : List of OutputPort
+isAllowedToSendThroughThisLink() : Boolean
«interface»
GeneralEntity
+getEntityId() : Integer
+getEntityName() : Name
«interface» +getFullName() : Name
Port +getSystemName() : Name
+isLocal() : Boolean
+getOwner() : GeneralEntity
+getLink() : Link
«interface» «interface» «interface» «interface»
InputPort OutputPort ComponentLevelEntity RemoteEntity
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11. SimArch Data Interfaces (2/2)
«interface»
«interface»
Comparable
Event
+getData() : Object
+getRecipient() : GeneralEntity
«interface» +getRecipientName() : Name
Time +getSender() : GeneralEntity
+decreaseBy() +getSenderName() : Name
+decreasedBy(in time : Time) : Time +getTag() : Enum
+getValue() : Double +getTime() : Time
+increaseBy(in time : Time)
+increasedBy(in time : Time) : Time
+isEqualTo(in time : Time) : Boolean «interface»
+isGreaterOrEqualThan(in time : Time) : Boolean Name
+isGreaterThan(in time : Time) : Boolean +getValue() : String
+isLesserOrEqualThan(in time : Time) : Boolean +setValue(in name : String)
+isLesserThan(in time : Time) : Boolean
+setValue(in time : Double)
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12. SimArch implementation status
 Layer 1
• DDESoverHLA library: provides a DES
abstraction on top of HLA
 Layer 2
• SimJ library: provides generic simulation
components
 Layer 3
• jEQN library: provides the primitives for
defining EQN simulation models
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13. jEQN
A Domain-Specific Language
for the simulation of
Extended Queueing Networks
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14. Domain Specific Language (DSL)
 Programming language
 Domain-specificity
 Increased expressiveness (decreased
generality)
 Ease-of-use
 Reduced domain and programming
expertise
 Verificability and transformability
 Declarative
 Enabler of reuse
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15. jEQN: a DSL for EQNs
 Based on:
• Domain analysis of EQN models
• Declarative approach (specify what to simulate
rather then how to simulate)
 Used to:
• Reduce the semantic gap between the model
specification and the corresponding simulation
program
 Composed of:
• Simulation services defined by SimArch
• Set of EQN simulation components
• Set of parameters for the components
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16. jEQN Simulation Components
 Derived from EQN domain analysis
 6 groups:
• user sources
• waiting systems
• service centers
• routers
• special nodes
• support components
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17. jEQN Parameters
 Design guidelines:
• Decouple jEQN simulation components from
the parameters that do not affect the
simulation logic
• Flexible parameter structure to allow the
incorporation of additional parameter types
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18. Example candidate parameters
• For user source components:
 termination condition
 interarrival time
 user generation
• For waiting system components:
 preemptive waiting systems
 preemption policy
 queue structure
 service request generator
 enqueueing and dequeuing policy
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19. Categories of Parameters
1. Parameters used to take decisions
• routing policy, enqueueing policy
2. Parameters that provide sequence of
values
• interarrival times, service request times
(incorporating jRand)
3. Parameters that provide storage support
• queues
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20. Category-1 parameters
• Organized around four variables:
 T: the decision data
 I: the input data
 S: the state data
 D: the type of decision
• According to the use of such variables, for
example:
 StateOnlyDecisionPolicy
 InputOnlyDecisionPolicy
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21. Category-1 parameters
«interface»
Policy
«interface» «interface»
InputPolicy StatePolicy<S>
+getDecision() : D
+getState() : S
+setState(in s : S)
«interface»
ImplicitInputPolicy<I> «interface» «interface»
ExplicitInputPolicy<T extends DecisionData, InputAndStatePolicy
+getImplicitInput() : I D> StateOnlyDependentPolicy<S, D>
+setImplicitInput(in i : I)
+getDecisionFor(in t : T) : D -state : S
+getDecision() : D
«interface» ImplicitAndExplicitInputDependentPolicy<I, ExplicitInputOnlyDependentPolicy<T,D>
ImplicitButNotExplicitPolicy<I,D> T,D>
+getDecisionFor() : D -implicitInput : I
ImplicitButNotExplicitInputDependentPolicy<
I,D> ImplicitAndExplicitInputAndStateDependentPolicy<
-implicitInput : I I,S,T,D>
+getDecision() : D -state : S
+getImplicitInput() : I
+setImplicitInput(in i : I)
ImplicitButNotExplicitInputAndStateDependentPolicy<
I,S,D>
-state : S
+getState() : S
+setState(in s : S)
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22. Category-3 parameters
«interface»
UserQueue MaskBasePolicy<?,?,?,UserQueue>
+getNumberOfUserEnqueued() : Integer *
-userWithdrawer
+insert(in u : User) 1
1
+extract() : User
1 1 1
FiniteUserQueue InfiniteUserQueue MultiUserQueue
1
-queueAssigner
1 1
-decisionDataFactory
1
-queue
1
-enqueueingPolicy
«interface»
java.util.List
1 1
1
MaskBasePolicy<?,?,UserBasedDecisionData, QueueAssigner
Integer> -decisionDataFactory
1 1
1
-dispatchingPolicy
UserBasedDecisionDataFactory
1
MaskBasePolicy<?,?,UserBasedDecisionData,
UserQueue>
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23. Model-driven Development of
Distributed Simulators
Example Application
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24. The Catenet System
Host A
LAN1 (token ring)
WAN
Host B
GW1 GW2
LAN2 (ethernet)
catenet
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25. EQN Model
(high-level)
catenet
GET
TCP
Source LAN1 LLC/
GW1
IP
TCP TCP IP
(Host A) MAC802.5
Host A
X.25
network layers
WAN
X.25
Host B
network layers
RELEASE
Sink
TCP
LLC/
IP
GW2 MAC802.3
LAN2 IP TCP TCP
(Host B)
Window
Size C
Token
Pool
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26. EQN Model
(LAN1 details)
Msg
Tok
?
createMsg allocMsg allocTok getToken setSender transfrm putToken relTok decrfrm routing destrMsg
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27. Model-driven Development (1/3)
 Direct mapping between EQN model
entities and SimArch/jEQN
 SimArch statements: environment set-up,
connections between jEQN components
 jEQN components: model entities and
their parameters
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28. Model-driven Development (2/3)
 EQN model entities and jEQN components:
 Service Center  jEQN Service Center
 Waiting System  jEQN Waiting System
 Passive Queue (Pool of Tokens, Activate and Release
Nodes)  jEQN Special Nodes
 EQN entity properties and parameters (to be set at
instantiation time) of jEQN components:
 Enqueueing policy: FIFO
 Service Time: Normal Stream
 Operation: setSender (for setSender node)
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29. Model-driven Development (3/3)
 Extra jEQN components for the routing
information (implicitly included in the EQN
model)
 Parameterization of jEQN components
according to the model properties (service
time, enqueueing policy, routing policy, etc.)
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30. Example Derivation of
Simulator Code from the Model (1/2)
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31. Example Derivation of
Simulator Code from the Model (2/2)
jRand
jEQN
Policy
Framework
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32. Local Simulator Development
1. Instantiate a Layer 2 implementation
(Execution Container)
2. Declare and define jEQN components
according to the previous guidelines
3. Connect components
4. Activate the execution container
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33. From Local to Distributed
1. Partition the model
2. Configure Layer1 components (e.g.
FederationManager, with, e.g., number
of simulators, lookahead, etc.)
3. Code each simulator (federate)
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34. Model Partitioning
Submodel 0
Host A
LAN1 (token ring)
WAN Submodel 2
Host B
GW1 Submodel 1
GW2
LAN2 (ethernet)
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35. Coding the distributed simulator
1. Instantiation of a distributed implementation of Layer 2,
which in turns requires Layer 1
2. Declaration and definition of jEQN components
1. Local: as in the local simulator
2. Remote: use of SimArch RemoteEntity
3. Connection between jEQN components
1. Local-Local: as in the local simulator
2. Local-Remote: similarly to local connection, with a
local proxy for the RemoteEntity
4. Activation of the execution container
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36. Simulators deployment
US - Georgia Italy
jEQN
Simulator
jEQN
SimArch Simulator
HLA over IIOP CORBA-HLA
Client
SimArch
GATech's CORBA -HLA
jEQN
Simulator
LAN WAN Camerino
Client
HLA over IIOP SimArch
Ascoli CORBA -HLA
Client
Ge orgia Te ch
HLA o
ve r IIOP
TorVe rgata
CORBA RTI Server
CORBA-HLA
Client Le cce
SimArch
jEQ N
Simulator
SimLab
Key
Federate
CORBA-HLA CORBA-HLA CORBA-HLA
Client Client Client
IIOP protocol
Server
Pitch protocol over TCP and UDP Executive
Federation
Manager SimArch SimArch
pRTI 1516
jEQ N jEQ N
Simulator Simulator Local
CORBA + CORBA-HLA
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37. Simulator Validation
 Local simulator
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38. Simulator Validation
 Distributed simulator
End-to-end delay [s]
Time [s]
100
90
80
70
60 C=4
50 C=7
40 C=12
30
20
10
0
0 1 2 3 4 5
lambda [packets/s]
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39. Conclusions
 SimArch eases the development of
distributed simulators by introducing a set
of layered abstract simulation services on
top of the distributed environment
 SimArch advantages:
• Reduces development effort and time
• Does not need specialized distributed
simulation skills
• Facilitates the introduction of simulation
languages as DSLs (e.g., jEQN)
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