What a UofA is

The Unit of Assurance is the smallest independently verifiable bundle of credibility evidence for computational modeling and simulation. It packages the credibility decision — who judged what, against what criteria, using what evidence, with what result — as a signed, provenance-linked, machine-verifiable engineering artifact.

One UofA per Context of Use

UofA models credibility assessment at the COU level, not the individual factor level. Each UofA packages the complete credibility decision for one Context of Use, including all per-factor assessments as embedded CredibilityFactor nodes and any detected quality gaps as WeakenerAnnotation nodes.

Morrison Blood Pump Assessment
├── morrison/cou1/uofa-morrison-cou1.jsonld (ProfileComplete)
│   COU1: CPB Use (Class II) — Model Risk Level 2
│   ├── hasContextOfUse    → COU1 node
│   ├── bindsRequirement   → hemolysis safety requirement
│   ├── bindsModel         → ANSYS CFX v.15.0 + Eulerian HI model
│   ├── bindsDataset       → [PIV data, hemolysis in vitro data]
│   ├── hasValidationResult → [mesh convergence, PIV velocity, hemolysis comparison]
│   ├── hasCredibilityFactor → [13 V&V 40 factors: 7 assessed + 6 not-assessed]
│   ├── hasWeakener        → [W-AL-01 ×3, W-AR-05 ×3, W-EP-02 ×3, W-ON-02, W-CON-04]
│   ├── hasDecisionRecord  → "Accepted for COU1"
│   ├── hash               → sha256:<real hash>
│   ├── signature          → ed25519:<real signature>
│   └── wasDerivedFrom     → Morrison DOI
│
└── morrison/cou2/uofa-morrison-cou2.jsonld (ProfileComplete)
    COU2: VAD Use (Class III) — Model Risk Level 5
    └── ... (same structure, different decision and weakener profile)

Shared entities (model, datasets, geometry) are referenced by IRI rather than duplicated. The divergence between COU1 and COU2 weakener profiles is the central analytical demonstration: same model, same data, different model risk produce measurably different credibility evidence.

Two profiles

Profile	Use case	Required fields
Minimal	Lightweight audit trail, live pipeline capture, early-stage projects	7
Complete	Regulatory submissions, formal V&V 40 assessments, full credibility arguments	All Minimal + model bindings, credibility factors, provenance, quality metrics

The profiles are computable. SHACL shapes enforce the field set for each profile. See C1, C2, C3 for how this enforcement works.

Standards alignment

UofA is standards-anchored, not standards-replacing. It packages evidence for assessments performed against existing credibility frameworks.

Standard	Pack	Factor count	Level range
ASME V&V 40-2018	vv40	13	1–5
NASA-STD-7009B	nasa-7009b	19 (13 shared + 6 NASA-only)	0–4
FDA 2023 CM&S Guidance	(uses vv40)	13	1–5
DO-178C aerospace software	(planned, post-defense)	—	—

Multiple packs can be loaded simultaneously. The CLI loads core SHACL plus pack-specific shapes additively. See Reference → CLI for the --pack flag.

Design principles

Principle	Meaning
Minimal	Small JSON-LD document, human-readable, one file per COU
Semantic	Aligns with PROV-O, V&V 40, and domain ontologies
Verifiable	Real SHA-256 hashes, ed25519 signatures, SHACL validation
Composable	UofAs form nodes in system-level assurance graphs via wasDerivedFrom
Tool-agnostic	Works with any simulation tool, MBSE platform, or ML pipeline
Hide the plumbing	Practitioners see completeness reports and gap alerts, not triples and SPARQL