bernard p. zeigler arizona center for integrative modeling and simulation
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Interoperability, Automation, Built-in Evolution: the DEVS Framework for Coping with Emerging Complexity. Bernard P. Zeigler Arizona Center for Integrative Modeling and Simulation University of Arizona, Tucson and RTSync Corporation. IT Systems Developmental Complexity?. - PowerPoint PPT PresentationTRANSCRIPT
Interoperability, Automation, Built-in Evolution: the DEVS Framework for Coping with Emerging
Complexity
Bernard P. Zeigler Arizona Center for Integrative Modeling and Simulation
University of Arizona, Tucsonand
RTSync Corporation
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IT Systems Developmental Complexity?
• IT Systems Developmental Complexity = degrees of developmental freedom
× interdependence of design decisions
× special requirements of environments
• IT Complexity explosion – is driven by faster, cheaper computers, networking, web middleware, …, – Emergence: each stage enables the next stage with accelerating options for
further growth– Wherever choices in platform, language,…, line of code, are possible, different
developers will make different choices– Underlying structure/behavior dependencies force local decisions to have
global impact breaking neat design patterns– Environments impose a plethora of special situations and an exponentially
growing number of parameter combinations.2
• Consequences of complexity explosion:– Proliferation of incompatible variations on same themes– Ubiquitous heterogeneity– Vertical integration - “Stove piping”
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Response: Model-Driven Development Methodology • is increasingly being adopted for software-intensive system development• In this context, model is an abstract representation of software code, that
– is technology independent– can survive technology changes– can be implemented in multiple code instantiations– enables reuse and automation
UML (Unified Modeling Language)
• Is the most widely used framework to support model driven development
• Promoted by Object Management Group as a standard within its Model Driven Architecture (MDA)
• Supported by increasingly powerful commercial tools• Enhanced by SysML supporting requirements front end• Incorporated in architectural frameworks: DoDAF,
MoDAF, …
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Issues In Developmental Complexity of IT Systems
• Often development does not start from scratch• Conditioned by idiosyncratic requirements • Powered, but unconstrained, by applicable standards• Requires legacy subsystem integration• Rigorous testing is needed to cope with complexity• Methodology must scale with growth and evolution of
system• UML/MDA offers only limited support to address these
concerns
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Formulate the Issues within a Formal System of System Models (SoSM) Concept
• SoSM = collection of disparate system models to be federated to satisfy new simulation requirements
• Each participating system model may itself be large and complex
• Participant models usually have become efficient at achieving their own specialized requirements
• Participant models often adhere to idiosyncratic formalisms and development approaches
• Distinguish between interoperation and integration to set appropriate objectives
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Interoperation vs Integration*
Interoperation of system components
• participants remain autonomous and independent
• loosely coupled• interaction rules are soft coded• local data vocabularies persist• share information via mediation
Integration of system components• participants are assimilated into whole,
losing autonomy and independence• tightly coupled• interaction rules are hard coded• global data vocabulary adopted• share information conforming to strict
standards
* adapted from: J.T. Pollock, R. Hodgson, “Adaptive Information”, Wiley-Interscience, 2004
NOT Polar Opposites!
reusabilitycomposability
efficiency
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DEVS Framework• Discrete Event Systems Specification (DEVS) is the basis for a formal framework
for modeling and simulation • DEVS contributes to scalability by:
– Offering a standard for distributed simulation to support interoperability, composability, and reuse
– Exploiting the separation between model, experimental frame and simulator– Fostering model continuity and progressive development– Automating and integrating complex systems implementation and testing– Emulating the biological brain for its "built-in" correlation of activity and
behavior to drive efficient evolution via component re-us
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DEVS is not a technique, method or technology… But it can leverage technology to add implement its
contributions … in particular Web Service Technology
Web Service Oriented Architecture Basis for M&S
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Language and platform independent =>separation of specification and implementation
Loosely coupled => message based, synchronous and asynchronous
interactions.Net-Centric =>
No centralized control, use of established protocols, security considerations.
Inter-operable =>Standards based
Observable => agents can inspect service requests/responses
Transport protocol HTTP/HTTPS request/response
Data Encoding SOAP (Simple Object Access Protocol), XML Schema
Interface Description WSDL (Web Services Description Language)
Service Description and Discovery UDDI (Universal Description, Discovery and Integration)
Security WS-Security, XML-Signature, XML-Encryption, ...
Emerging infrastructure =>Net-Centric Enterprise Services on the Global
Information GridBasis for Model Registration and Discovery =>
Meta-Data RegistryBasis for Simulation => Web server and service development frameworks
( .Net, AXIS)Emerging advances => Mediation services, Semantic Web
Data Type Schema and InstancesData Type Schema and Instances
SOAPSOAP
XMLXML
Network Layers
ServicesServices RegistriesRegistries DataData
Approach to Current Issues in SoSM
• Adopt Web-enabled M&S Concepts for composing SoSM
• Exploit SOA infrastructure for Model Repository and Component Reuse
• Develop Formal Dynamic SoSM Distributed Simulation Standard
• Build on this foundation to support Higher Levels of Interoperability
• Develop automated and integrated development and testing methodology
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SOA-enabled Model Repository Composability and Reuse *
* adapted from: ZEIGLER, B. P. 1997. A framework for modeling & simulation. Applied Modeling & Simulation:An Integrated Approach to Development & Operation, McGraw-Hill, New York.
Requirement In relation to Supports
Components and Coupling
Creating new compositions composabilityreusability
building block components for application areas
defining a small number of “primitives” for synthesizing a wide variety of models for specific domain
expressabilityreusability
hierarchical modular model construction
input/output ports for both building block components and coupled models
composabilitycomplexity management
experimental frame base indexing
supports discovery of frames instantiated in the model base that are related to a desired frame for given objectives
meta data characterizationdiscovery
accommodate multiple formalisms
enable using different types of models with specific semantics, advantages, and limitations
expressabiltyinteroperability
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Success Story: DEVS-based Joint MEASURE – Model Repository Reuse*
Note presence of discrete and continuous dynamic model typesNote presence of discrete and continuous dynamic model types
“… the Lockheed-Martin activities may well represent the state of the art in complex model composability …”,
Improving the Composability of Department of Defense Models and Simulations, P.Davis and R.Anderson RAND, 2004
GPS III
*Advanced Simulation Center, Lockheed Martin Corp., Sunnyvale, CA
Use of infrared model in JCTS
project
Use of infrared model in JCTS
project
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Linguistic Levels of Information Exchange and Interoperability
syntactic
semantic
pragmatic
syntactic
semantic
pragmatic
LinguisticLevel
A System of Systems or services interoperates at this level if :
Pragmatic – how information in messages is used
The receiver re-acts to the message in a manner that the sender intends (assuming non-hostility in the collaboration).
Semantic – shared understanding of meaning of messages
The receiver assigns the same meaning as the sender did to the message.
Syntactic –common rules governing composition and transmitting of messages
The consumer is able to receive and parse the sender’s message
System Participant System Participant13
DEVS Model SpecificationDEVS Model Specification
SOAPSOAP
XMLXML
DEVS Simulation ProtocolDEVS Simulation Protocol
Network Layers
ServicesServices
DEVS Standardization Supports Higher Level Web-Centric Interoperability
DEVS Protocol specifies the abstract simulation engine that correctly simulates DEVS atomic and coupled models
•Gives rise to a general protocol that has specific mechanisms for:•declaring who takes part in the simulation•declaring how federates exchange information•executing an iterative cycle that
controls how time advancesdetermines when federates exchange messagesdetermines when federates do internal state updating
DEVS Simulation Concept
DEVS Protocol
DEVSSimulator
DEVSModel
Note: If the federates are DEVS compliant then the simulation is provably correct in the sense that the DEVS closure under coupling theorem guarantees a well-defined resulting structure and behavior.
Note: If the federates are DEVS compliant then the simulation is provably correct in the sense that the DEVS closure under coupling theorem guarantees a well-defined resulting structure and behavior.
syntacticsemantic
pragmatic
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SchemataSchemata RegistryRegistry
Web-enabled interoperability of DEVS components
IP NetworkIP Network
DEVScoordinator
DEVScoordinator
DEVS coupledModel
DEVS coupledModel
DEVSJAVA client
JRE
DEVS Simulator ServicesIn C++
DEVS Simulator ServicesIn C++
DEVSModelDEVS
Model
aDEVS FederateaDEVS Federate
Microsoft web serverMicrosoft web server
.Net .Net
DEVS Simulator ServicesIn JAVA
DEVS Simulator ServicesIn JAVA
DEVSModelDEVS
Model
DEVSJAVA FederateDEVSJAVA Federate
Apache tomcat serverApache tomcat server
AXIS2
ProxiesProxies
DEVSMessages
DEVSNamespace
DEVSNamespace
SOAPmessages
• DEVS Message Class is defined in the formalism• Schemata for entity classes in Message are stored in namespace• DEVS Federates can register and discover schemata for information exchange
• DEVS Message Class is defined in the formalism• Schemata for entity classes in Message are stored in namespace• DEVS Federates can register and discover schemata for information exchange
Supports re-use, composability, andinteroperability
Supports re-use, composability, andinteroperability
Can be automated for JAVA using Dynamic Invocation
Can be automated for JAVA using Dynamic Invocation
Simulator Services
Simulator Services
Non-DEVS Federate Non-DEVS Federate
web serverweb server
Biologically Inspired Assessment for Component Re-use
DEVS Simulator Services
DEVS Simulator Services
DEVSModelDEVS
Model
DEVS FederateDEVS Federate
Web serverWeb server
DEVScoordinator
DEVScoordinator
DEVS coupledModel
DEVS coupledModel
DEVS Coordinator
JRE
IP NetworkIP Network
DEV
SAg
ent
DEV
SAg
ent
Mission ThreadEvaluation
Mission ThreadEvaluation
ActivityTracking
ComponentCredit
Assignment
ComponentCredit
Assignment
Information for Future Component Re-use
HttpRequests/responses
Correlations of activity with Mission Thread Success
Correlations of activity with Mission Thread Success
Component benefit and resource cost in context
Component benefit and resource cost in context
collector
collector
DEVS-Based Net-Centric Systems Test Agent Capability
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Mission Thread
Information Exchange
Network Monitoring
Middleware
Mission Effectiveness
System Performance
PragmaticAgents
SemanticAgents
SyntacticAgents
T&E Instrumentationsites
servers
usersclients
networks
workstations
Summary • Model-driven methodology employs technology-independent software
abstractions, e.g., in UML, to support diverse implementation platforms and enable reuse and automation
• Existing interoperability standards do not provide needed separation between models and simulations and do not effectively constrain object models
• System of System Modeling (SoSM) concepts go beyond UML/MDA to address issues in interoperability, composability, and reuse
• DEVS system theory –based framework operationalizes SoSM concepts and supports automated, rigorous testing in realistic GIG/SOA environments
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devsworld.org www.acims.arizona.edu Rtsync.com
Books and Web Links
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More Demos and Links http://www.acims.arizona.edu/demos/demos.shtml
• Integrated Development and Testing Methodology: • AutoDEVS (ppt) & DEMO
– Natural language-based Automated DEVS model generation – BPMN/BPEL-based Automated DEVS model generation
– Net-centric SOA Execution of DEVS models
– DEVS Unified Process for Integrated Development and Testing of SOA
• Intrusion Detection System on DEVS/SOA
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DEVS/SOA Infrastructure: Supports Deployment and Execution of DEVS Models on the Web
WEBSERVICECLIENT
Middleware (SOAP, RMI etc)Net-centric infrastructure
DEVS Simulator Services
DEVS Modeling Language (DEVML)
DEVSJAVA
DEVSAgent
( Virtual User)
DEVSAgent
(Observer)
WEBSERVICECLIENT
Run Example
• 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
1. MAJ Smith tasks Intel to reconnoiter objective area and provide threat estimate
2. Posts taskings using Discovery and Storage
5. Intel Cell issues alert via messaging 6. MAJ Smith pulls estimate from Storage
3. Intel Cell initiates high priority collection against objective, and collectors post raw output
4. Intel posts products via Discovery and Storage
Observing Agent for Major Smith
Observing Agent for Intel Cell
NCES GIG/SOA
• Test agents are DEVS models and Experimental Frames
• They are deployed to observe selected participant via their service invocations
notes time of posting
Observing Agent alerts other Agent
Computes Time for Task,Measure Performance
sends time to other Agent
Example of GIG/SOA Example of GIG/SOA Mission Thread TestingMission Thread Testing
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