Model Validation Ontologies for Government Reference Architectures

Dr. Rick Graves and Mr. Harry Byers

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Aerospace Systems Directorate

Air Vehicles Division

Distribution Statement A: Approved for Public Release; Distribution is Unlimited. PA# AFRL-2023-0157

Distribution Statement A: Approved for Public Release; Distribution is Unlimited. PA# AFRL-2023-0157

Background & Purpose

• Model validation hierarchy framework developed through NATO/STO task group
• Collaboration between AFRL, NASA LaRC, MBDA (UK), and WLO Consulting
• Outlines connection between system design requirements down to physics-informed modeling and simulation capabilities
• Identify and prioritize capability gaps and resource allocations for experiments
• Evaluate the Systems Modeling Language (SysML) and Cameo Systems Modeler
• Development of model validation hierarchies
• Implementation of model validation hierarchies into model-based systems architectures
• Semantically apply SysML to the design of model validation hierarchy
• A model validation hierarchy is a digital artifact
• Resource investment to develop this digital artifact
• Adoption of these artifacts into digital engineering pilots and pathfinders will serve to realize investment value

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Distribution Statement A: Approved for Public Release; Distribution is Unlimited. PA# AFRL-2023-0157

Model Validation Hierarchy Artifacts

• Addresses system design requirements
• Systems architecture driven by requirements
• Requirements flow down into modeling and simulation activities
• Reduction of complexity through decomposition
• Arbitrary number of tiers for hierarchy/ontology organization
• Complexity reduced as hierarchy is further decomposed into lower tiers
• Transition tier to connect systems architecture with modeling and simulation activities
• Perspective shift
• Modular Ontology Approach
• Developed to support re-use of existing hierarchies and adapt them to new requirements

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Distribution Statement A: Approved for Public Release; Distribution is Unlimited. PA# AFRL-2023-0157

Ontology Elements

• SysML model elements
• Constituents of a system model
• Represent system structure, behavior, requirements, and constraints
• Blocks, Properties, Activities, Actions, etc.
• Organized into Package elements
• SysML diagrams
• Diagram ≠ system model
• Used to provide a view of, and construct, the underlying system model
• Model validation hierarchy elements
• Constituents of a model validation hierarchy
• Represent systems, subsystems, components, and physics-informed models
• Organized into tiers
• Superior and Subordinate across tiers
• Singular and Collective within tiers
• Coupled

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Distribution Statement A: Approved for Public Release; Distribution is Unlimited. PA# AFRL-2023-0157

Ontology Relationships

• Between elements within the same tier
• Composition (SysML)
• SysML - Whole-part relationship
• Hierarchy - Relate collective elements to sub-elements
• Association (SysML)
• SysML - Form references between elements
• Hierarchy - Relate elements to define coupled elements
• Between elements within different tiers
• Aggregation (SysML)
• SysML - Functionally identical to associations, visually different
• Hierarchy - Decompose higher tiered elements into lower tiered elements
• Allocation (SysML)
• SysML - Cross-cutting relationship
• Hierarchy - Cross the boundary from the transition tier to a systems architecture tier

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Missile System Example – Systems Architecture + Transition

• Missile-oriented model validation hierarchy for a notional air defense systems architecture
• Missile system and subsystems represented by independent blocks (SysML)
• System structure described through usage of Compositions (SysML)
• Transition tier connected to systems architecture through Allocations (SysML)
• Perspective shift from systems-oriented view to modeling-oriented view

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Distribution Statement A: Approved for Public Release; Distribution is Unlimited. PA# AFRL-2023-0157

Missile System Example – Physics Taxonomy

• Focus on aerodynamic & structural models
• Tiers organized into nested Packages (SysML)
• In general, a physics taxonomy tier has its own Package
• Packages shown to highlight hierarchy tiers
• Tier changes described by usage of Aggregations (SysML)
• Care must be taken to maintain readability on diagrams
• Contains scope

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Distribution Statement A: Approved for Public Release; Distribution is Unlimited. PA# AFRL-2023-0157

Future Work

• Additional collaborative ontology research with partner organizations required
• Profile Development
• Extends SysML
• Defines model validation hierarchy-specific semantics, including relationships (ontology)
• Identify metadata tags that may be associated with model validation hierarchy elements
• Metamodel
• Establish what constitutes a “well-formed” model validation hierarchy described using SysML
• Establish when to use certain SysML relationships, elements, etc.
• Style Guide
• Establish conventions for naming, diagram layout, etc.
• Create rules for how a SysML model is read, modified, and integrated collaboratively
• Hierarchy Element Prioritization (HELP) and Gap Analyses implementation in Cameo
• Identify and connect system response quantities (SRQs) to validation hierarchy elements
• Rank validation hierarchy element impact to SRQs and prioritize validation experiments
• Identify capability gaps and high-priority activities to close gaps

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Distribution Statement A: Approved for Public Release; Distribution is Unlimited. PA# AFRL-2023-0157

Questions?

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Distribution Statement A: Approved for Public Release; Distribution is Unlimited. PA# AFRL-2023-0157

Distribution Statement A: Approved for Public Release; Distribution is Unlimited. PA# AFRL-2023-0157