DEVS Namespace for
Interoperable DEVS/SOA
Chungman Seo
Bernard P. Zeigler
Arizona Center for Integrative Modeling and Simulation
The University of Arizona
Outline
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Motivation of the study
Objectives
Background
Design of interoperable DEVS simulation environment
Implementation of interoperable DEVS simulation
environment
Track Display Application
HLA vs. SOA support for DEVS interoperability
Conclusions
Future work
The Problem
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DEVS simulators implement the DEVS modeling formalism in diverse
programming environments, e.g. DEVSJAVA, ADEVS, CD++,
DEVSim++, PythonDEVS
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This situation
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The DEVS formalism specifies the same abstract simulator algorithm for
any simulator
Different simulators implement the same abstract simulator using
different codes
inhibits interoperating DEVS simulators
prevents simulation of heterogeneous models
Each simulator can not provide platform-neutral message passing
The Need for Interoperability
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Different platforms specialize in different capabilities, e.g., C++
supports fast execution, but JAVA provides a better platform for web
service development
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Reusability of Models increases through interoperability
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In our applications at JITC, ADEVS based on C++ is employed for radar
track generation while DEVSJAVA is used for track display
System of Systems (SoS) requires interoperability to compose new
systems from existing systems
Interoperability requires well-defined interfaces to use systems in
different platforms or languages
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Web services, HLA, and CORBA provide communication channels
between software systems with different platforms
DEVS Standardization Supports Higher
Level Web-Centric Interoperability
Prior Work
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Mittal and Rico developed DEVS/SOA
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it employs JAVA serialization to code messages into byte array
this restricts interoperation to simulators based on JAVA, e.g.
DEVSJAVA, and XDEVS
It does not use DEVS namespace
Taekyu Kim extended DEVS/SOA to run in real time but
did not address interoperability
Moath Jarrah developed a Negotiation Model and
simulated it on DEVS/SOA but did not implement it in web
services
Objectives
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To design and implement interoperable DEVS Simulation
environment using SOA and DEVS namespace
To manage DEVS namespace for interoperable DEVS
Simulation environment
To implement neutral message passing between different
DEVS simulation environments
To show implementation of layered interoperability
concept
Platforms and languages neutral DEVS simulation
environment using SOA
Background - DEVS Modeling and
Simulation Framework
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Set theory based system
specification formalism
Atomic model : lowest level model,
contains structural dynamics
Coupled model : composed of one
or more atomic and / or coupled
-> hierarchical construction
Basic Parallel DEVS Model:
M = <X, Y, S, δint, δext, δcon, λ ta>
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X : set of input events
Y : set of output events
S : set of states
δint : internal transition function
δext :external transition function
δcon : confluent function
λ : output function
ta : time advance function
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Time base is logical time
Background - SOA (ServiceOriented Architecture)
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An architectural approach to
build software application
that use services available in a
network
Language and platform independent =>
separation of specification and implementation
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Loosely coupled =>
message based, synchronous and asynchronous
interactions.
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Over the Internet =>
No centralized control, use of established protocols,
security considerations.
Registry
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Inter-operable =>
Standards based.
Contract
Find
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Register
Transport protocol
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Data Encoding
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Bind & invoke
Service Consumer
Service Provider
SOA’s Find-bind-execute paradigm
WSDL (Web Services Description Language)
Service Description and Discovery
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SOAP (Simple Object Access Protocol), XML Schema
Interface Description
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HTTP/HTTPS
UDDI (Universal Description, Discovery and Integration)
Security
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WS-Security, XML-Signature, XML-Encryption, ...
Web Service
Overall System of Interoperable DEVS
Simulator Services with DEVS
namespace
Register DEVS
message types
Use DEVS
message types
DEVS Name Space
Schema
Schema
Use DEVS message types
Web
service
DEVS
Simulator
Service
Common
Interface
(WSDL)
Service
Provider 1
OS 1 / Language 1
Common
Interface
(WSDL)
Simulation
protocol
Simulation
protocol
Web Server 1
DEVS
Simulator
Service
OS 2 / Language 2
Web Server 2
DEVS Simulator Services
Integration/Execution
user
Web
service
Service
Provider 2
Web-enabled interoperability of
DEVS components
DEVS namespace
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Network accessible schema document
Storage for types of messages which
are used in DEVS models
A unique element name in the DEVS
namespace
Register and extract domain specific
schema through a web service
Supports re-use, composability, and
interoperability
<xsd:schema xmlns:ns0="http://devs.service" xmlns:xsd="http://www.w3.org/2001/
XMLSchema" attributeFormDefault="qualified" elementFormDefault="qualified"
targetNamespace="http://devs.service">
<xsd:element name="EFP">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Job" type="ns0:Job"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:complexType name="Job">
<xsd:sequence>
<xsd:element name="id" type="xsd:int"/>
<xsd:element name="time" type="xsd:double"/>
</xsd:sequence>
</xsd:complexType>
<xsd:complexType name="TrackData">
<xsd:sequence>
<xsd:element name="xposition" type="xsd:double"/>
<xsd:element name="yposition" type="xsd:double"/>
<xsd:element name="heading" type="xsd:double"/>
</xsd:sequence>
</xsd:complexType>
<xsd:element name="TrackGenerator">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="TrackData" type="ns0:TrackData"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
The Structure of DEVS Simulator Service
• Web Service displayed to clients
• Link between DEVS M&S and
WS operations
• Convert DEVS message to XML message
• Implement DEVS M&S with various
Languages ( Java, C++, Python, Matlab)
• Manage Networking and SOAP
DEVS Web Service
operations
DEVS Interface
DEVS Modeling & Simulation
Web Service Middleware
(AXIS2 or .Net)
The operations of DEVS simulator
service
DEVS Simulation protocol
operations
void getSimulator(boolean)
void initialize(double)
double getTN()
void lambda (double)
String getOutput()
void receiveInput(String,String,String)
void deltfcn(double)
void addCoupling(String,String,String)
void exit()
Schema location and Message
type operations
String getSchemaInfo()
String getType(String)
String[ ] getInports()
String[ ] getOutports()
Reporting function operations
String getConsole(String)
String getResult()
DEVS message to XML message
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DEVS message consists of a port/value pairs
Implementation of DEVS message is
different in different DEVS implementations
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DEVSJAVA : employs a message class
for DEVS message
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ADEVS : PortValue class is used for
ADEVS message
<Message>
<content>
<port>out</port>
<entity>
<class>Job</class>
<id type=”int”>9</id>
<time type=”double”>0.0</time>
</entity>
</content>
<content>
.
.
.
</Message>
XML message
DEVS Message
DEVS Message / XML
Message Convertor
XML Message
Web Sevice Middleware
XML Message
SOAP
DEVS M&S
DEVS Interface
DeSerialize XML to DEVS
Serialize DEVS to XML
Web Service
NetWork
Track Display Application
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Shows interoperability between DEVS models in
different implementation languages
Consists of a TrackDisplay model and
TrackGenerator models
The TrackGenerators generate time indexed
TrackData behavior
The TrackDisplay has a capability of displaying
track data in GUI
Uses a message type called TrackData consisting
of four variables
id : int xposition : double yposition : double
heading : double
Coordinator
DEVSJAVA
TrackGenerator 1
Model
ADEVS
TrackGenerator 2
Model
Virtual Time
Simulation
AXIS2 environment
Apache web server
.Net environment
Microsoft web server
SOAP
messages
SOAP
messages
TrackDisplay for web service using AXIS2
SOAP
messages
IP Network
HLA vs. SOA support for DEVS
interoperability
DEVSsimHLA
Interoperable DEVS/SOA
Platform/Language
interoperability
Support
Support
Neutral Message passing
No
Support
Middleware
interoperability
Possible using a HLA
bridge
Support
Linguistic levels of
interoperability
Support 2 levels
(syntactic and semantic)
Support all levels
(syntactic, semantic, and
pragmatic)
Conclusions
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Designed and Implemented an interoperable
DEVS Simulator services with DEVS namespace
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Applied to DEVSJAVA and ADEVS
Developed the web service for handling DEVS
namespace to provide semantic level
interoperability between DEVS simulator services
Implemented the platform-neutral message
passing on the interoperable DEVS Simulation
environment
Future Work
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Design/Implement pragmatic level
interoperability
Apply interoperable DEVS simulator service to the
other DEVS implementations (DEVS python, DEVS
Matlab, and so on)
Add more functions to the web service for
handling the DEVS namespace
Extend the platform-neutral message passing to
support complex message types
Thank you
Implement the DEVS namespace
Schema
1
Schema
3
Provider
Register GUI
Schema
2
User
Browsing GUI
Web Service for
DEVS namespace
DEVS
Namespace
Example of Registration /Extraction of
DEVS message
Domain : EFP
Message type : Job
Variable : id type : int
Variable : time type : double
Web
Service
Operation
Web
Service
Operation
Web Service
Operation
Web Service
Operation
Registration
Extraction
DEVS simulator service for DEVSJAVA
The Structure of DEVSJAVA
message
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Message
Content
port
Entity
Job
id
time
Content
XMLObjectMessageHandler
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DEVSJAVA Modeling & Simulation
DEVSJAVA interface between
operations and DEVSJAVA
simulator
DEVSJAVA message to XML
message
AXIS2 to generate a DEVS simulator
service
Java based web service on Apache
tomcat server
XML Document for DEVSJAVA
message
<Message>
<content>
<port>out</port>
<entity>
<class>Job</class>
<id type=”int”>9</id>
<time type=”double”>0.0</time>
</entity>
</content>
<content>
.
.
.
</Message>
Simulator classes for virtual time and real time simulations
A Atomic class contains DEVS atomic or coupled model using a
Digraph2Atomic class
A Digraph2Atomic class which pretends to be an atomic model to follow
DEVS protocol during simulation of interoperable DEVS simulator services
A XMLObjectMessageHandler class to convert DEVSJAVA message to XML
message vice versa
DEVS Interface
DEVS simulator service for ADEVS
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ADEVS modeling and
simulation
ADEVS interface between
operations and ADEVS
simulator
ADEVS message converter
.Net to generate a DEVS
simulator service
C++ based web service on
Microsoft web server
ADEVS Interface simulator
string converter of C++ to VC++ vice versa
ADEVS message converter
ADEVS Interface
ADEVS API
Modeling API
adevs_models.h
adevs_digraph.h
adevs_simpledigraph.h
adevs_wrapper.h
Simulation API
adevs_simulator.h
adevs_sched.h
Container API
adevs_bag.h
adevs_set.h
object_pool.h
ADEVS Library
The Structure of ADEVS
message
XML Document for ADEVS message
Bag
PortValue
type
port
value
Job
Message
Converting
id
time
PortValue
<Message>
<content>
<port>1</port>
<entity>
<class>Job</class>
<id type=”int”>9</id>
<time type=”double”>0.0</time>
</entity>
</content>
<content>
.
.
</Message>