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

andJoint Interoperability Test Command

Fort Huachuca, AZ 85613-7051zeigler@ece.arizona.edu

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&SBody of

Knowledge

M&STheory and Framework

DoD Architectural Framework

MetaData

Mediation

Services

Start with Largest Perspective: M&S Body of Knowledge

• 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

Tuncer I. Ören, Toward the Body of Knowledge of Modeling and SimulationInterservice/Industry Training, Simulation, and Education Conference (I/ITSEC) 2005

Core elements of supporting disciplines

mathematics, computer science, systems science, systems engineering

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

M&S knowledge for application– science, engineering, business…

• Training, Education and learning• Development• Decision support• Understanding and Analysis• Entertainment 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

Concepts/terminology of supporting disciplinesare likely to be incorporated into M&S COImetadata characterizations or be in need of mediation

Theory of Modeling and Simulation provides anintegrating framework for these elements

M&SBOK provides “checklist” to enumerateM&S meta-data, mediation and services

M&S Framework and System Theory Support*

“Theory of Modeling and Simulation” (Zeigler, Praehofer and Kim, Academic Press, 2000)

Framework for M&S

Ontology delimiting entities andrelationships in M&S

Mathematical SystemsTheory

rigorous supports manipulating elements in their real-world incarnations to achieve the desired relationships

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*

Real WorldReal World SimulatorSimulatorSimulatorSimulator

modelingrelation

simulationrelation

Each entity is represented as a dynamic system

Each relation is represented by a homomorphism or other equivalence

Data: Input/output relation pairs

structure for generating behaviorclaimed to represent real world

Device forexecuting model

Model

“Theory of Modeling and Simulation” (Zeigler, Praehofer and Kim, Academic Press, 2000)

M&S Entities and Relations (cont'd)

Real WorldReal World

modelingrelation

simulationrelation

Experimental frame specifies conditions under which the system is experimented with, observed and controlled

• captures modeling objectives• needed for validity, simplification justifications

SimulatorSimulator

Model

Experimental Frame

AbstractModel

Morphismsat

Structure Level

Morphismsat

Behavior Level

Morphismsat

Structure Level

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

Joint MEASURE - Mission Effectiveness Analysis Simulator for Utility, Analysis and Evaluation

• 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

The Distributed Joint MEASURETM

Architecture

Logger

PropagatorPlatform

Sensors

Weapons

C3

Hull

Platform

Sensors

Weapons

C3

Hull

GIS

GIS dB

Logger

PropagatorPlatform

Sensors

Weapons

C3

Hull

Platform

Sensors

Weapons

C3

Hull

GIS

GIS dB

Hull Hull

HLA/RTI

Endomorphs Endomorphs

Joint MEASURE – Model Repository Reuse

Note presence of discrete and continuous dynamic model types

Use of infrared model in JCTS

project

“… 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

Prescriptive Requirements for Simulation Model Repositories *

* 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

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

enabled by “self-containedness” with input/output ports, both for building block components and models resulting from coupling

composabilitycomplexity 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 characterizationdiscovery

accommodate multiple formalisms in a manner satisfying the previous requirements

enable using different types of models with specific semantics, advantages, and limitations

expressabiltyinteroperability

Network

DEVS Simulator

DEVS Model

Middleware

Syntactic

Semantic

TechnicalInteroperability

Pragmatic

Conceptual

Tolk’s Levels

DEVS Simulator

DEVS Model

Middleware

SystemsArchitecture

DEVS component models are correctly integrated into a higherlevel coupled model by the DEVS simulator protocol

Middleware-Independent Simulation Architecture for SOA Infrastructure

Parallel and sequential simulation of the same DEVS model will always produce the same resultsThis 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

Service Discovery: UDDI

DEVS Distributed Executor

DEVS Model

Sevice Description: WSDL

Packaging:XML

Messaging:SOAP

Communication: HTTP

SOA

DEVS Simulator

DEVS Model

Pre-test of ConceptualModel in non-distributedenvironment

Refine and Transfer model to distributedenvironment

DEVS Distributed Simulator

DEVS Model

Packaging:XML

Messaging:SOAP

Communication: HTTP

• Change engine•Provide meta-data forWeb presence as service

The model can remain basically invariant as it is transitioned through the phases from conception to realization

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 Simulationas 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

Bernard P. Zeiglerzeigler@ece.arizona.edu

ACIMSwww.acims.arizona.edu

Contact:

More information:

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