Outline Systems interoperability (vs integration) Roles of - PDF document

CRITICAL ISSUES IN C4I 20-21 May 2008 George Mason University, Fairfax, VA Towards a Formal Standard for Interoperability in M&S/System of Systems Integration Xiaolin Hu Bernard Zeigler, Saurabh Mittal Arizona Center for Integrative Dept of Computer Science, Modeling and Simulation, Georgia State University, University of Arizona, Atlanta, GA Tucson, AZ xhu@cs.gsu.edu {zeigler | saurabh} @ece.arizona.edu Outline • Systems interoperability (vs integration) • Roles of Modeling and Simulation in System of Systems • Why middleware (HLA) is not enough • Levels of Interoperability – from conceptual to linguistic • Testing interoperability at multiple levels • DEVS standard for simulation interoperation • Application to testing the GIG/SOA • Summary

Interoperation vs Integration* Interoperation of components Integration of components • participants remain autonomous and • participants are assimilated into independent whole, losing autonomy and independence • loosely coupled • tightly coupled • interaction rules are soft coded • interaction rules are hard coded • local data vocabularies persist • global data vocabulary adopted • share information via mediation • share information conforming to strict standards reusability efficiency composability NOT Polar Opposites! * adapted from: J.T. Pollock, R. Hodgson, “Adaptive Information”, Wiley-Interscience, 2004 Problem formulation: Systems of Systems System of defining obstacle is Systems (SoS) lack of interoperability interoperate among components disparate systems C4I to synthesize Systems a new functionality M&S as Solution Methodology M&S as Smart Component

Tolk’s Levels of Conceptual Interoperability Model Level of Conceptual Characteristic Key Condition Interoperability Conceptual The assumptions and constraints Requires that conceptual models be underlying the meaningful documented based on engineering abstraction of reality are aligned methods enabling their interpretation and evaluation by other engineers. Dynamic Participants are able to Requires common understanding of comprehend changes in system system dynamics state and assumptions and constraints that each is making over time, and are able to take advantage of those changes. Pragmatic Participants are aware of the Requires that the use of the data – or the methods and procedures that context of their application – is each is employing understood by the participating systems. Semantic The meaning of the data is Requires a common information shared exchange reference model Syntactic Introduces a common structure to Requires that a common data format is exchange information, used Technical Data can be exchanged between Requires that a communication protocol participants exists Stand alone No interoperability Linguistic Levels of Interoperability pragmatic semantic syntactic Linguistic Interoperability Example Level Demonstrated if: Pragmatic – The receiver reacts to A commander’s order is obeyed by the How information in the message in a troops in the field as the commander message is used manner that the intended. (This assumes semantic sender intends interoperability.) Semantic – The receiver assigns An order from a commander to multi- Shared understanding of the same meaning as national participants in a coalition meaning of messages the sender did to the operation is understood in the same message. manner despite translation into different languages. Syntactic – The consumer is able A common network protocol (e.g., IPv4) Common rules governing to receive and parse ensures that all nodes on the network composition and the sender’s message can send and receive data bit arrays transmitting of messages while adhering to a prescribed format.

Mapping M&S Layers to Linguistic Levels Collaboration Layer Semantic Web, Composition, Orchestration Design and Test Development Layer Pragmatic Level SES, DoDAF, Integrated System Development and Testing Experimental Frame Layer . Observers and Agents for Net-Centric Key Performance Parameters Modeling Layer Semantic Level Ontologies, Formalisms, Model Dynamic Structure, Life Cycle Continuity, Model Abstraction Execution Layer Abstract Simulators, Real time Execution, Animation Visualization Syntactic Level Network Layer Distributed Grids, Service Oriented Architectures Background: DEVS M&S Framework Discrete Event Systems Specification (DEVS) Experimental Frame • Based on mathematical formalism using system theoretic principles Source Simulator System • Separation of Model, Simulator and Experimental Frame Simulation Modeling Relation • Atomic and Coupled types Relation • Hierarchical modular composition Model Level Name System Specification at this level 4 Coupled System built from component systems with coupling recipe. Systems 3 I/O System System with state and state transitions to generate the Structure behavior. 2 I/O Collection of input/output pairs constituting the allowed Function behavior partitioned according to initial state of the system. The collection of I/O functions is infinite in principle because typically, there are numerous states to start from and the inputs can be extended indefinitely. message 1 I/O Collection of input/output pairs constituting the allowed Behavior behavior of the system from an external Black Box view. 0 I/O Frame Input and output variables and ports together with allowed values.

DEVS Modeling and Simulation Infrastructure supports simultaneous testing at multiple levels Mission Thread Test Agents Control and Observe collaborations Pragmatic Level Tests DEVS acceptors alert Pragmatic Level agents higher layer agents of Semantic Level agents inform Semantic Level network conditions that observe message exchanges agents of the objectives for invalidate test results between collaboration health monitoring participants Semantic Level Tests Semantic Level agents network probes return activate probes at statistics and alarms to Syntactic Level DEVS transducers/ acceptors Syntactic Level Tests DEVS Modeling Language (DEVML) DEVS Simulator Services Middleware (SOAP, RMI etc) - Net-centric infrastructure DEVS Simulation Concept • Specifies the abstract simulation engine that correctly simulates DEVS atomic and coupled models DEVS Simulator • Gives rise to a general protocol that has specific mechanisms for: DEVS • declaring who takes part in the simulation: Protocol format for referencing federates (participants) o • declaring how federates exchange information: o format for their message exchange patterns DEVS Model • executing an iterative cycle that • controls how time advances: o updating the clock based on next event times • determines when federates exchange messages: o the point in the cycle when all interchange takes place • determines when federates do internal state updating o the point in the cycle when next event times are collected 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.

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”) Core Simulator Interface Core Simulator Interface DEVS DEVS Non-DEVS Simulator Simulator Simulator DEVS DEVS ? Atoimc1 Atoimc2 Model Model 2 1 Concept of DEVS Standard Single DEVS C++ Simulation processor Protocol Distributed Java Simulator DEVS DEVS DEVSML Real -Time Model Core Simulator Simulator Interface Interface Virtual-Time Non Simulator Other DEVS Representation

Core Simulator Interface interface coreSimulatorInterface{ void setSimulators(Collection<CoreSimulatorInterface>); void initialize(); simulators. simulators. tellAll tellAll ("initialize“) ("initialize“) Double nextTN(); simulators. simulators. AskAll AskAll (“nextTN (“nextTN ”) ”) void computeInputOutput(Double t); simulators. simulators. tellAll tellAll (" ("computeInputOutput”) simulators. simulators. tellAll tellAll ("sendMessages ("sendMessages ") ") void applyDeltFunc(Double t); simulators. simulators. tellAll tellAll (" (" void putContentOnSimulator( ApplyDeltFunc”) CoreSimulatorInterface sim, ContentInterface c); void sendMessages(); } Core Simulator Interface is derived from the DEVS simulation cycle It specifies the methods and arguments to be coordinated under the DEVS protocol DEVS/SOA Infrastructure: Supports Deployment and Execution of DEVS Models on the Web WEB SERVICE CLIENT DEVS DEVS Agent Agent (Observer) ( Virtual User) WEB DEVSJAVA SERVICE CLIENT DEVS Modeling Language (DEVML) DEVS Simulator Services Middleware (SOAP, RMI etc) Net-centric infrastructure • Service Oriented Architecture (SOA) consists of various W3C standards • Client server framework • XML Message encapsulated in SOAP wrapper Run Example • Machine-to-machine interoperability over the network based on WSDL interface descriptions