DEVS and SES as a Framework for Modeling and Simulation Tool Development

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DEVS and SES as a Framework for Modeling and
Simulation Tool Development

• Bernard P. Zeigler
• Arizona Center for Integrative Modeling and
  Simulation
• University of Arizona

Presented at SIMUTools 2008 March 37 2008
Marseille, France
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MS Framework

• Based on mathematical formalism using system
  theoretic principles
• Separation of Model, Simulator and Experimental
  Frame
• Atomic and Coupled types
• Hierarchical construction

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Discrete Event Time Segments
X
t1
t0
t2
S
e
y0
Y
4
MS Framework formulated within UML
MS Framework classes
create classes to satisfy use cases
Use Cases
interpretation as software code (e.g. Java)
UML
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DEVS Formal Specification of a System

• A discrete event system specification (DEVS) is a
  structure
• MltX,S,Y,?int, ?ext, ?con, ?,tagt
• where
• X is the set of input values,
• S is a set of states,
• Y is the set of output values,
• ?int S-gtS is the internal transition
  function,
• ?ext,Q?X-gtS is the external transition
  function,
• ?con,Q?X-gtS is the confluent transition
  function,
• ta S-gtR 0,8
• Where
• Q(s,e)s?S, 0 ?e? ta(s) is the total state
  set,
• e is the time elapsed since last transition,
• ?S-gtY is the output function and
• R 0,8 is the set of positive reals with 0
  and ?

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DEVS Hierarchical Modular Models
System Entity Structure
SES
Hierarchical Composition, Coupling and Variants
are Represented in System Entity Structure
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Some Types of Models Represented in DEVS
Coupled Models
Atomic Models
Partial Differential Equations
can be components in a coupled model
Ordinary Differential Equation Models
Processing/ Queuing/ Coordinating
Networks, Collaborations
Physical Space
Spiking Neuron Networks
Spiking Neuron Models
Processing Networks
Petri Net Models
n-Dim Cell Space
Discrete Time/ StateChart Models
Stochastic Models
Cellular Automata
Quantized Integrator Models
Self Organized Criticality Models
Fuzzy Logic Models
Reactive Agent Models
Multi Agent Systems
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Concept of DEVS Standard
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DEVS Simulation Protocol
simulators.
tellAll
("initialize)
simulators.
tellAll
("initialize)
Coordinator
Coordinator
simulators.
AskAll
(
nextTN
)
simulators.
AskAll
(
nextTN
)
simulators.
tellAll
("
computeInputOutput
)
simulators.
tellAll
("
computeInputOutput
)
simulators.
tellAll
("
sendMessages
")
simulators.
tellAll
("
sendMessages
")
simulators.
tellAll
("
simulators.
tellAll
("
ApplyDeltFunc)
putContentOnSimulator
Non-DEVS Simulator
DEVS Simulator
DEVS Simulator
?
DEVS Model 2
DEVS Model 1
Atoimc1
Atoimc2
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Finite Deterministic DEVS FD-DEVS
FDDEVS ltincomingMessageSet, outgoingMessageSet,
StateSet, TimeAdvanceTable, InternalTransitionTab
le, ExternalTransitionTable,OutputTablegtwhereinc
omingMessageSet, outgoingMessageSet, StateSet are
finite setsTimeAdvanceTable StateSet ? R0,8 
(the positive reals with zero and
infinity)InternalTransitionTable StateSet ?
StateSetExternalTransitionTable StateSet
incomingMessageSet ? StateSet, OutputTable
StateSet ? the set of subsets of outgoingMsgSet

• Natural Language For FDDEVS
• to start hold in PHASE for time SIGMA
• when in PHASE and receive MSG go to PHASE
  lteventuallygt
• hold in PHASE for time SIGMA
• after PHASE then output MSG
• from PHASE go to PHASE

Semantics defined by mapping into DEVS
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FD-DEVS

• The right abstraction of DEVS retains
  important timing properties
• Amenable to analysis
• Supports automation
• Maps to DEVSJAVA
• Supplies a skelton that can be extended to full
  DEVS
• Simple XML expression

• Example of Natural Language Spec
• to start passivate in waitForStart
• when in waitForStart and receive StartAck go to
  sendFirst
• hold in sendFirst for time 0.5 then output
  ReqForAck and go to sendSecond
• hold in ackReceived for time Infinity

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Automated Analysis Based on State Input Pairs
Enables Automated Test Model Generation
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Generated Test Models in DEVSJAVA SimView
AckCheck
Observe Outputs
Send inputs
Observe Pass/Fail
Trigger next in Sequence upon pass
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System Entity Structure (SES) SESBuilder
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System Entity Structure/Model Base Repository
Support Automated DEVS Generation and Reuse
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Automated Generation of Test Models
Augmented Test Models
Automated
manual
FDDEVS atomic model
SES
SES/XML Of DSR texts
FDDEVS test models
Pruned ES
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DEVS/SOA Infrastructure Supports Deployment and
Execution of DEVS Models on the Web

• Service Oriented Architecture (SOA) consists of
  various W3C standards
• Machine-to-machine interoperable interaction over
  the network based on WSDL interface descriptions
• Client server framework
• Message encapsulated in SOAP wrapper which is in
  XML

Run Example
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Deploying Models DEVSML and DEVS/SOA
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Applications

• Natural language capture of high level
  information technology systems requirements
• Automated generation of FDDEVS kernel
  DEVSJAVA/C models for distributed real-time
  net-centric IT systems testing
• Development of web service workflows using
  DEVS/SOA
• Network Traffic data capture, focused extraction,
  and model generation for exercising IT systems
  e.g., intrusion detection

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Conclusions

• DEVS and SES provide a framework based on Systems
  Theory for MS tool development
• DEVS standard supports sharable models and
  repository reuse
• The framework provides an ontology in which tools
  can be organized and interoperate missing slots
  can be identified overlapping tools can be
  compared
• The framework supports development of generic
  tools which in turn support a wide array of
  domain specific specializations and applications

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Books and Web Links
acims.arizona.edu
Rtsync.com
devsworld.org