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The Need for a Theory of Modeling and Simulation to Support the M&S COI Mission Bernard P. Zeigler, Ph.D., Arizona Center for Integrative Modeling and Simulation and Joint Interoperability Test Command Fort Huachuca, AZ 85613-7051 [email protected] Premise: Coordination is needed, theory can help The M&S COI has partitioned its interests into metadata, mediation, and services, recognizing, at the same time, that applications will not break down neatly into these categories. A framework is needed to • provide an ontology for M&S that recognizes the essential dynamic character of simulation models, • properly distinguish the elements in the M&S enterprise and the relationships that connect such elements in meaningful ways related to the objectives of simulation exercises, • provide a rigorous mathematical theory that supports manipulations of the elements in their real-world incarnations in order to achieve the desired relationships • enable us to – – – derive meaningful metadata schemes to characterize the identified elements help delineate services amenable to web-based manipulation provide well-defined semantics and pragmatics for cross-COI mediation. Potential problems in the absence of an M&S COI Framework • Lack of accepted terminology: multiple definitions for basic terms (model, simulation) make coherent vocabulary of metadata registry problematic • Difficulties in composability of models and simulations come to the fore: WSDL characterizations of M&S service components are likely to break down when new orchestrations are attempted due to incompatibilities that can’t be represented at the interface level • Central feature of M&S – dynamics (time behavior) – is the key impediment to easy interoperability of simulations as services • others… Where Theory of M&S Fits M&S Body of Knowledge M&S Theory and Framework DoD Architectural Framework MetaData Mediation Services Start with Largest Perspective: M&S Body of Knowledge Tuncer I. Ören, Toward the Body of Knowledge of Modeling and Simulation Interservice/Industry Training, Simulation, and Education Conference (I/ITSEC) 2005 • • A Body of Knowledge (BOK) for modeling and simulation (M&S) provides a comprehensive and integrative view of the discipline A systematic top-down decomposition of M&SBOK – Definition: simulation is goal-directed experimentation using dynamic models M&S knowledge for application – science, engineering, business… • Training, Education and learning • Development • Decision support • Understanding and Analysis • Entertainment Core elements of M&S discipline • Input data • Models and modeling • Model processing • Experimentation • Model behavior • Behavior generation • Behavior processing • M&S infrastructure • Computerization • User/system interfaces • Reliability and ethics Core elements of supporting disciplines mathematics, computer science, systems science, systems engineering M&SBOK provides “checklist” to enumerate M&S meta-data, mediation and services Application types signal services that are likely to be of interest to external users: other communities of interest (COI) with which M&S COI must interact Theory of Modeling and Simulation provides an integrating framework for these elements Concepts/terminology of supporting disciplines are likely to be incorporated into M&S COI metadata characterizations or be in need of mediation M&S Framework and System Theory Support* Framework for M&S Ontology delimiting entities and relationships in M&S Mathematical Systems Theory rigorous supports manipulating elements in their real-world incarnations to achieve the desired relationships “Theory of Modeling and Simulation” (Zeigler, Praehofer and Kim, Academic Press, 2000) Mathematical Theory of Systems • levels of system specification –are the levels of structure and behavior at which we can describe dynamic systems • systems specification formalisms – these represent the types of models, such continuous and discrete, that modelers can use to build dynamic system models – a formalism specifies a subclass of systems Levels of System Specification and Associated Morphisms: Formal Basis for Multiple Levels of Abstraction Level Specification Name Two Systems are Morphical at this level if: 0 Observation Frame their inputs, outputs and time bases can be put into correspondence 1 I/O Behavior they are morphic at level 0 and the time-indexed input/output pairs constituting their I/O behaviors also match up in one-one fashion 2 I/O Function they are morphic at level 0 and their initial states can be placed into correspondence so that the I/0 functions associated with corresponding states are the same 3 State Transition the systems are homomorphic (explained below) 4 Coupled Component components of the systems can be placed into correspondence so that corresponding components are morphic; in addition, the couplings among corresponding components are equal M&S Entities and Relations* Device for executing model Real World Simulator Data: Input/output relation pairs modeling relation Each entity is represented as a dynamic system Each relation is represented by a homomorphism or other equivalence simulation relation Model structure for generating behavior claimed to represent real world “Theory of Modeling and Simulation” (Zeigler, Praehofer and Kim, Academic Press, 2000) M&S Entities and Relations (cont'd) Experimental Frame Morphisms at Behavior Level Real World modeling relation Experimental frame specifies conditions under which the system is experimented with, observed and controlled • captures modeling objectives • needed for validity, simplification justifications Simulator simulation relation Model Morphisms Morphisms atat Structure StructureLevel Level Abstract Model Examples of the M&S theory that might be the basis for scaling up to the SOA • Lockheed’s Model Base Repository • Middleware Independent Distributed Simulation Protocol • Semi-automated generation of standards conformance testing Lockheed’s Managed Modeling Approach to DEVS-Based Modeling and Simulation • DEVS – Discrete Event System Specification – Formal discrete event specification. – Clearly separates Simulation Engine from Models. – Object passing In-ports and Out-ports – Interchangeable Coupled & Atomic Models. – Strong support for reuse and composability. • Multiple implementation are available. • GUI development environments are available • Active developer community distributed worldwide. Joint MEASURE Advanced Simulation Development Tool for Systems of Systems • Advanced Analyst-oriented GUI. • Models SoS Engagement Domain. • Platforms (how they move and react), • Sensor (& networks), • Communications (& networks), • Weapons (& systems), • C3 (at multiple levels). • High Performance Simulation Engine • Managed Software • Full Complement of Integrated Tools Joint MEASURE - Mission Effectiveness Analysis Simulator for Utility, Analysis and Evaluation TM The Distributed Joint MEASURE GIS dB GIS dB GIS GIS C3 Sensors Hull Weapons Sensors Sensors Hull Platform Weapons Weapons Propagator Propagator Platform C3 Architecture Hull Platform Logger Logger C3 Sensors C3 Weapons Hull Platform Endomorphs Hull HLA/RTI Hull Endomorphs Joint MEASURE – Model Repository Reuse “… the Lockheed-Martin activities may well represent the state of the art in complex model composability …”, Davis, Paul and Anderson, Robert in Improving the Composability of Department of Defense Models and Simulations, RAND, 2004 Use of infrared model in JCTS project Note presence of discrete and continuous dynamic model types Prescriptive Requirements for Simulation Model Repositories * Requirement In relation to Supports building block components for application areas defining a small number of “primitives” for synthesizing a wide variety of models for specific domain expressability reusability hierarchical modular model construction enabled by “self-containedness” with input/output ports, both for building block components and models resulting from coupling composability complexity management coupling templates standardized means to couple the building blocks interoperability experimental frame base indexing supports discovery of frames instantiated in the model base that are closely related to a desired frame for given objectives meta data characterization discovery accommodate multiple formalisms in a manner satisfying the previous requirements enable using different types of models with specific semantics, advantages, and limitations expressabilty interoperability * adapted from: ZEIGLER, B. P. 1997. A framework for modeling & simulation. Applied Modeling & Simulation: An Integrated Approach to Development & Operation, McGraw-Hill, New York. Middleware-Independent Simulation Architecture for SOA Infrastructure Conceptual Systems Architecture Pragmatic Tolk’s Levels Semantic DEVS Model DEVS Model Syntactic DEVS Simulator DEVS Simulator Technical Interoperability Middleware Middleware Network DEVS component models are correctly integrated into a higher level coupled model by the DEVS simulator protocol Parallel and sequential simulation of the same DEVS model will always produce the same results This is a strong proof of correctness that no logical-processor-based proof has been able to rival. DEVS Model Continuity as Basis for Life Cycle Development of Web Services DEVS Model DEVS Simulator DEVS Model Pre-test of Conceptual Model in non-distributed environment The model can remain basically invariant as it is transitioned through the phases from conception to realization DEVS Distributed Simulator DEVS Model DEVS Distributed Executor Packaging:XML Messaging:SOAP Communication: HTTP SOA Service Discovery: UDDI Sevice Description: WSDL Refine and Transfer model to distributed environment Packaging:XML Messaging:SOAP Communication: HTTP • Change engine •Provide meta-data for Web presence as service Model-Driven Development (MDD)* for SOA (Service Oriented Architecture) • Organizations must integrate MDD into the development process for distributed, heterogeneous, loosely coupled service environment • Models – – – – represent the problem domain raise the level of abstraction serve as blueprints drive the development process • Facilitate creating and managing complicated systems – – – – • Use/Re-use model-based code generators Accelerate/Automate the software life cycle Transition study of systems capable of expansion and evolution Reduce manual work required in development and testing Deliver higher-quality service components *Anne T. Manes, Burton Group Pub. Summary: Dynamic Systems and Semantics • Dynamics are a major component in the semantics of simulation models • Dynamic properties must be represented in schemes for semantic layers of model interoperability • Model formalisms key in on different features of dynamics (e.g., continuous, discrete event) • Multiple formalisms need to be managed in any M&S repository supporting reusability and composability Summary: DEVS-based SOA Development • Simulation Model framework supported by: – Systems Theory-based – Formal, allows proofs of correctness and other properties – Dynamics – integrates model formalisms in one theory and framework • Modularly separates – Model – Simulator – Experimental Frame • Model Continuity supports development life cycle Theory of Modeling and Simulation as Framework for M&S COI • • Formally characterizes the elements and relationships to support discovery, interoperability and composability Ontology identifies the elements as dynamic systems within mathematical systems theory – well-defined levels of behavior and structure specifications – relationships are made operational by appropriate morphisms – rigorous mathematical theory supports orchestration of components • Provides the basis for metadata schemes that are unambiguous and compatible with the vocabulary and concepts of the theory – expose the proper elements for efficient discovery – reuse of M&S data and services. Results: • solid foundation for a well-defined semantics and pragmatics of the M&S enterprise • well-defined infrastructure for SOA development Contact: Bernard P. Zeigler [email protected] More information: ACIMS www.acims.arizona.edu Other Presentations • Standards Conformance Testing as an M&S Web Service • The Special Role of M&S in Cross-COI Mediation • M&S Services at the Crossroads of Service Oriented Architecture and the DoD Architectural Framework