E2 · Publication Volume 24

Model and Interpretation Entities

contact, fault, domain, surface, solid, scenario and version

Learning objectives

• Explain why contact, fault, domain, surface, solid, scenario and version require explicit semantic modelling.
• Design identities, relations and constraints that preserve model and interpretation entities across exchange.
• Separate hard release gates from diagnostic metrics and interpretation choices.
• Produce a versioned model manifest with scenario, topology and change evidence from synthetic evidence.

The lesson is complete only when the learner can defend both the model and the release decision. A neat schema without evidence, tests or declared limitations is an unverified design. The assessed artefact must make assumptions visible and distinguish source assertions from derived conclusions.

Decision context

A model package must let a reviewer identify which scenario and version produced a decision product, which evidence it consumed and which assumptions constrained it. A file timestamp or final-looking filename cannot reliably answer those questions.

Start with a decision record: name the intended use, the evidence required, the consequence of error, the accepted uncertainty and the role authorised to accept residual risk. Then ask whether the proposed model can answer the decision question without relying on filename conventions, row order, undocumented defaults or someone’s memory. This prevents technology selection from concealing a missing semantic requirement.

The same record may be fit for one use and unfit for another. A rapid exploratory view can tolerate conditions that a released exchange package cannot. Fitness is therefore stated against a use, contract version and quality gate rather than attached permanently to the data.

Core concept

A geological model is a versioned interpretation assembled from evidence and assumptions. Contacts and faults organise topology; domains classify regions; surfaces and solids encode geometry; scenarios express alternatives. None should be mistaken for an unchanging observation.

The working scope is contact, fault, domain, surface, solid, scenario and version. For each item in that scope, distinguish the thing itself, the label used by a source, the claim made about it and the record that carries the claim. Identity is not a display name; a value is not its unit; an observation is not a model; current is not the same as valid. These distinctions create explicit places for correction, uncertainty and competing interpretations.

A good semantic design can be explained as a set of sentences before it is encoded. Each sentence identifies a subject, a property or relationship, an object or result, and the context under which the claim holds. Physical tables and files are then projections of those sentences, not their source of meaning.

Semantic model

Give scenario, model version, feature interpretation and geometry representation separate identities. A feature such as a fault may persist across versions while its geometry changes. A surface representation belongs to a specific version and parameter set. A solid derives from bounded surfaces and carries topology checks plus the coordinate reference definition.

Test every proposed record against seven questions: What has identity? What type is it? Which property or relationship is asserted? Which spatial and temporal context applies? Which state or qualifier modifies the assertion? Which evidence supports it? Which version and activity produced the stored representation? Missing answers become explicit contract gaps.

Normalisation is used to separate independent facts, not to maximise the number of tables. A compact nested object can be semantically sound if the same identities, constraints and provenance remain explicit. Conversely, a highly normalised database can still be ambiguous when relationships and units exist only in documentation or application code.

Constraints and invariants

| Invariant | Executable or review test | | --- | --- | | Scenario and version are distinct | A scenario groups assumptions; a version records a state of that scenario. | | Feature and geometry are distinct | Geometry replacement does not silently create or delete the interpreted feature. | | Dependencies are immutable per release | Released inputs, parameters and checksums cannot be edited in place. | | Topology is validated | Check closed solids, intended contacts, fault offsets and domain exclusivity. |

An invariant is a condition that must remain true across storage, export, correction and reprocessing. Implement it as close to the authoritative boundary as practical and repeat the check at exchange boundaries. Record rule identifier, version, severity, evaluated scope, observed value and outcome so a failure can be reproduced.

Hard gates protect identity, semantic validity, required provenance and authorised use. Diagnostic checks reveal unusual values or patterns but require interpretation. Never convert a diagnostic threshold into deletion or correction without a reviewed rule and preserved source evidence.

Quantitative reasoning

Track model change with measures that match the representation: surface displacement statistics, changed volume V_c, domain transition counts and topology-test results. A useful normalised indicator is R_c = V_c / V_t, where V_t is the comparison volume. Always pair the number with a map of where change occurred.

Every reported ratio states its numerator, denominator, exclusions and evaluation time. Stratify results by source, entity type, contract version or processing run where aggregation could hide a local failure. Counts accompany percentages so a seemingly large change based on a tiny denominator remains visible.

Precision is part of meaning. Do not add decimal places merely because a storage type permits them, and do not round identity, interval or coordinate fields without a declared tolerance and test. Quantitative summaries support a release decision; they do not replace semantic review.

Evidence and uncertainty

Model uncertainty has structural, parametric and observational components. Alternative fault connectivity is structural uncertainty; interpolation settings are parametric; uncertain contacts are observational. Preserve these components so a scenario ensemble is not reduced to an unexplained collection of files.

Build an evidence packet containing preserved source reference, acquisition or assertion context, applicable method, validation results, reviewer decision and links to derivatives. Classify uncertainty as observational, semantic, structural, parametric or policy-related where that distinction changes treatment. “Unknown” is a valid state when the evidence cannot justify a stronger claim.

Contradictory evidence remains available. The model may select one current assertion, but the reason, competing assertion and effective time are retained. This makes later reinterpretation possible without pretending the earlier evidence never existed.

Interfaces and storage

A model exchange manifest identifies scenario, version, feature catalogue, coordinate reference, units, geometry files, dependencies, parameters, software-independent validation results and content fingerprints. Consumers should be able to reject a package before rendering if any required component is inconsistent.

Design an interface from the logical contract outward. Specify identifiers, types, cardinalities, units, value states, coordinate and time references, version negotiation, validation behaviour and structured errors before choosing a serialisation. The physical representation then declares its mapping to those logical elements.

Storage optimisation may partition, compress, index or cache data, but it must not change identity or silently remove context. A derived representation points to immutable inputs and a processing manifest. A cache carries freshness and contract-version information and is never treated as the only evidence copy.

Governance and access

Define release states such as working, reviewed, approved, superseded and withdrawn. Approval applies to an immutable version, never to a mutable folder. A superseding release points backward, records the reason for change and does not erase the version used by an earlier decision.

Governance is expressed through named roles, review states and versioned decisions, not through references to a particular organisation. Define who may propose, validate, approve, supersede and withdraw each governed resource. The audit trail records the role and event while avoiding unnecessary personal data.

Apply least-necessary access to source evidence and derivatives. Access controls must not erase identifiers, lineage or quality metadata needed to understand an authorised release. When policy is unresolved, quarantine the output with a precise reason and escalation route.

Integration checkpoint

The diagram summarises the control flow for this lesson. Read it from source evidence through semantic structure and validation to a decision-ready artefact. Each arrow should correspond to a declared relationship or transformation; each boundary should have a contract; each released node should have an identity, version and provenance pointer.

Integrate the lesson by adding a versioned model manifest with scenario, topology and change evidence to the evolving synthetic data package. Verify that earlier artefacts still resolve and that the new model does not overwrite observations, identifiers, values or versions introduced in previous lessons. Record every changed assumption.

Synthetic worked example

A synthetic model has two plausible fault-connectivity scenarios. Each scenario has a reviewed version with identical observation inputs but different structural assumptions. The learner assigns stable feature identities, fingerprints every geometry file, calculates changed volume and records which scenario fed a synthetic planning decision.

Work the example in four passes:

1. Preserve the received records and write the intended decision without correcting anything.
2. Identify entities, claims, context, uncertainties and policy constraints; mark every unresolved item.
3. Apply the versioned rules, create derivatives and record the exact transformation plus validation evidence.
4. Issue an accept, reject or quarantine decision and show how an independent reviewer can reproduce it.

Because the example is entirely synthetic, its values demonstrate method only. The important result is the chain from received evidence to justified decision. If a required fact is absent, the worked solution records the gap rather than manufacturing a plausible value.

Practice task

Create manifests for two synthetic model scenarios and two versions of one scenario. Separate feature identity from geometry identity, declare dependencies and assumptions, run topology tests, then write a comparison report that distinguishes evidence change, parameter change and structural change.

Use the following acceptance criteria:

• All required identifiers and references resolve to declared types.
• Every transformation preserves the received evidence and records its derivation.
• Invalid, unknown and inapplicable states remain distinct and machine-testable.
• The output identifies the contract, vocabulary and processing versions used.
• A second reader can reproduce the validation result without private knowledge.

Submit the source snapshot, authored contract or model, validation output, derivative, manifest and a short decision record. A screenshot alone is insufficient because it cannot demonstrate the exact input, version or rule execution.

Common failure modes

• A mutable file named final is treated as a release.
• Fault identity changes whenever its mesh is regenerated.
• Scenario assumptions exist only in a modeller’s memory.
• A closed-solid test is omitted because the model looks correct.

These failures share a pattern: convenient representation is mistaken for verified meaning. Diagnose the earliest boundary at which an assumption became implicit. Correct by restoring source evidence, making the assumption a versioned field or rule, rerunning dependent transformations and superseding—not overwriting—the affected release.

Do not repair a failure by adding an undocumented default. A blocked result with a specific missing dependency is safer and more reusable than a complete-looking result whose meaning cannot be reconstructed.

Review questions

1. How does a scenario differ from a version?
2. Why should a fault persist when its geometry changes?
3. Which measures reveal material model change?
4. What must an immutable release manifest contain?

For each answer, identify the governing invariant, the evidence needed to evaluate it and the appropriate release behaviour when the invariant fails. A strong answer distinguishes scientific uncertainty from missing semantics and distinguishes a recoverable warning from a hard contract violation.

Sources and further reading

• W3C PROV-O, a formal vocabulary for entities, activities, agents and derivation.
• Khronos glTF Registry, the normative registry for portable three-dimensional assets.
• OGC GeoSciML 4.1, an exchange model for geologic features, observations and vocabularies.
• NIST FIPS 180-4, secure hash algorithms used for content fingerprints.