Entailment Regime and Inference Semantics

Context and Problem Statement

opda’s ontology is emitted as three separated graphs — classes / shapes / annotations (ODR-0004 §3a) — and loaded into Apache Jena Fuseki by scripts/fuseki-load.mjs. Today that loader performs a plain Graph Store Protocol upload with no inference step: the live triplestore holds only asserted triples. The only entailment anywhere in the pipeline is the inference="rdfs" flag passed per call to pyshacl inside the BASPI5 round-trip harness (ADR-0014) — an implicit, validator-local behaviour, not a declared regime.

ODR-0002 admitted OWL 2 as a vocabulary and pinned RDF 1.2 and SHACL 1.2 by name, but committed to no OWL profile and no entailment regime, explicitly leaving that to a follow-up. opda therefore has no answer to a basic operational question: when data is loaded, which triples are entailed, and by what rules? The gap is not benign — ODR-0010 already warns that “loaded = active” is documentation-and-tooling, “silently incorrect with no reasoner to catch it,” and the round-trip’s correctness silently depends on RDFS entailment being switched on inside one validator.

Established prior art (recorded in §More Information) solved the same problem and ratified the result. That model — replicated here — is deliberately not full OWL: it materialises a small, curated, safe subset of OWL 2 RL at load time, keeps inference and SHACL validation as strictly separate stages, and runs SHACL on Apache Jena because pyshacl cannot validate SHACL 1.2. This ODR records the semantic decision (what entailments opda commits to, and what it deliberately refuses). The mechanisms are specified separately: load-time inference in ADR-0035, SHACL-1.2-via-Jena validation in ADR-0036.

Considered Options

• Option A (chosen) — Bounded entailment regime: RDFS + OWL 2 RL-safe rule subset, materialised at load time, full OWL DL out of scope. SHACL 1.2 via Jena as the constraint layer, kept strictly separate from inference; RDF 1.2 adopted in full on a Jena toolchain.
• Option B — Full OWL 2 DL classification (HermiT/Pellet/Konclude), the dormant opda-inference.ttl path. Rejected: unsound identity-merging and triple explosion in a master-data ontology, computationally heavy, explicitly out of the directed scope, and never built.
• Option C — Live Jena ja:reasoner (InfModel) at query time, as the primary mechanism. Rejected: Jena 6’s assembler cannot wrap an InfModel around a multi-graph TDB2 dataset without losing named-graph GSP upload (the prior-art project cited in §More Information hit exactly this and disabled its live reasoner), and it loses asserted-vs-inferred provenance.
• Option D — No entailment regime (status quo) — rely on per-call pyshacl inference="rdfs". Rejected: leaves “which triples are entailed?” undefined, couples entailment to one validator’s flag, and applies a broader (domain/range-including) RDFS than is safe.
• Option E — Full RDFS, including rdfs:domain/range entailment. Rejected: multi-domain properties mis-type individuals (R2); this is the direct cause of the EPCCertificate false positive.
• Option F — Defer RDF 1.2 triple-term syntax to stay rdflib-parseable (the prior-art path cited in §More Information). Rejected: it lets the weaker tool dictate the data model. opda already standardises on Jena (riot parses triple terms; jena-shacl validates SHACL 1.2), so the rdflib gap is not a constraint opda accepts.

Decision Outcome

Chosen option: “Option A — Bounded entailment regime: RDFS + OWL 2 RL-safe rule subset, materialised at load time”, because a small monotonic rule set yields the useful entailments — hierarchy, inverses, transitivity — that consuming queries and SHACL targets rely on, while refusing the OWL constructs that cause unsound identity-merging and triple explosion in a master-data setting.

opda adopts a bounded entailment regime: RDFS plus a curated OWL 2 RL-safe rule subset, materialised at Jena load time into a dedicated derived graph, with full OWL DL classification explicitly out of scope; SHACL 1.2 (via Jena) is the constraint/validation layer, kept strictly separate from inference; and RDF 1.2 is adopted in full — vocabulary and triple-term concrete syntax — on an Apache Jena toolchain that reads and writes it natively, so the standard drives the tooling rather than a parser’s limitations driving the standard. The justification: a small monotonic rule set yields the useful entailments — hierarchy, inverses, transitivity — that consuming queries and SHACL targets rely on, while refusing the OWL constructs (sameAs, Functional/InverseFunctional, equivalentClass/Property, domain/range typing) that cause unsound identity-merging and triple explosion in a master-data setting.

Consequences

• scripts/fuseki-load.mjs gains a load-time materialisation step (ADR-0035); the opda dataset then holds asserted + entailed triples in separate graphs.
• opda’s RDF toolchain standardises on Apache Jena — riot for parse/serialise, jena-shacl for validation (ADR-0036); rdflib/pyshacl are retired from the parse/validate path (not retained as a crutch), with the cut-over gated on demonstrated parity against the ODR-0010 capability floor.
• Statement-level annotation may use RDF 1.2 triple-term syntax going forward; the BASPI5 round-trip harness (ADR-0014) and any rdflib use in opda-gen migrate to Jena. opda does not downgrade the data model to remain rdflib-parseable — the anti-pattern is documented in the prior-art hand-off cited in §More Information.
• A new rule-contract artefact config/opda-rdfs-plus.rules (originally authored as opda-owl-rl-safe.rules; renamed per ODR-0029 R5) becomes a governed file.
• ODR-0004 §3a requires amendment to reflect R6 (the opda-inference.ttl re-scope) — a directing-authority edit (greenfield: no WG ratification gate), not a blocker on this ODR.
• The BASPI5 round-trip (ADR-0014) must validate against the R1 closure rather than ad-hoc full RDFS (R7); the EPCCertificate emitter mismatch should be fixed at source.
• ODR-0008 §Q6a’s “reasoner-independence test” baseline (written for entailment-off endpoints) must be re-read against a defined closure: hierarchy-admission queries now have a declared entailment to test against.
• Consuming SPARQL must expect symmetric/inverse/transitive duplicates from the closure and use DISTINCT / FILTER NOT EXISTS where appropriate.
• No emitted IRIs change and no new ontology terms are minted — this activates already-committed RDFS/OWL vocabulary; it does not extend the ontology.

More Information

• Refines: ODR-0002 — ontology language adoption (OWL 2 / RDF 1.2 / SHACL 1.2 pins).
• Bounds the “safe” set: ODR-0005 §R5 (no owl:sameAs), ODR-0017 §R6 (no sameAs materialisation; SHACL-AF pattern).
• Re-scopes: ODR-0004 §3a (three-graph separation; opda-inference.ttl projection row) — see R6.
• Validation contract: ODR-0013, ODR-0010 (overlay mechanism; pyshacl capability floor; “loaded ≠ entailed”).
• Perturbs baseline: ODR-0008 §Q6a (reasoner-independence test).
• Realised by: ADR-0035 (load-time inference materialisation), ADR-0036 (SHACL 1.2 via Jena).
• Consolidating doctrine: ODR-0033 — gathers §R1 (the frozen 7-rule closure as the only inference) and §R2 (the excluded set as non-evaluation, not a prohibition on authoring) into the single “author OWL/RDFS axioms as documentary AI-signal, never entailed” doctrine.
• Prior art (the replicated regime, the documentary-axiom anchors, and the data-model anti-pattern): ~/source/hm/semantic-modelling — hm ODR-0036 (SHACL rules & OWL inferencing; the owl:equivalentClass exclusion anchor), hm ODR-0014 (domain/range as documentation; the rdfs:domain/range exclusion anchor), council sessions 103/104/105 (Jena entailment architecture); config/hm-owl-rl-safe.rules; hm ADR-0022 (entailed-graph export), hm ADR-0147 (Jena SHACL 1.2). The §R5 “never let the weaker tool dictate the data model” anti-pattern (adopting RDF 1.2 then retiring triple-term syntax to stay rdflib-parseable) and its corrective hand-off are documented in docs/hm-handoff-rdf-1.2-triple-term-jena-fix.md.
• Implementation context: scripts/fuseki-load.mjs, docs/manual/physical-database/derived-profiles/opda-inference.md.

Rules

R1 — The enabled set: a sound, RL-incomplete RDFS-Plus application fragment

The load-time closure materialises exactly these constructs (the “Safe Group”). Each is monotonic and polynomial; together they are a strict subset of OWL 2 RL — a sound, RL-incomplete RDFS-Plus application fragment, NOT an OWL 2 RL reasoner (ODR-0029 R5). Removing rules from a sound rule set reduces completeness, never soundness; consumers MUST NOT assume the omitted domain/range, equality, or equivalence entailments hold (those are validated as SHACL, ODR-0029 R1/R3).

The canonical rule contract lives at config/opda-rdfs-plus.rules (ADR-0035), expressed in Jena GenericRuleReasoner syntax even though the load step hand-translates it to SPARQL INSERT. The rules file is the source of truth for which rules are safe. A disjointness consistency check (owl:disjointWith violation detection) is permitted but is a validation gate, not an entailment — it produces no domain triples (see ADR-0035).

R2 — The excluded set (this is the definition of “not full OWL”)

The following are forbidden from the load-time closure. The first three are already normative anti-patterns in opda’s own corpus:

This is what makes the regime RL-safe rather than RL or DL: no identity merging, no equivalence, no domain/range classification, no restriction reasoning.

R3 — Inference and validation are separate stages (“materialise, then validate — never mix”)

Load-time inference (R1) produces triples. SHACL (ADR-0036) consumes triples. The two MUST NOT be conflated: opda does not front SHACL with an OWL reasoner, and SHACL constraints are not expressed as OWL axioms (ODR-0004 R3 already fixes this — sh:minCount 1 is not owl:minCardinality). Where a constraint needs a derived triple that R1 does not produce, use a SHACL-AF sh:rule to pre-materialise only that triple (ODR-0017), never an OWL construct.

R4 — Materialisation target: a derived entailed graph, never a canonical source

Entailed triples are written to a dedicated derived named graph https://opda.org.uk/pdtf/graph/inferred/entailment, sibling to the per-module graphs. They MUST NOT be written back into opda-classes.ttl, opda-shapes.ttl, or opda-annotations.ttl (ODR-0004 §3a three-graph invariant and its CI tests). The entailed graph is derived, rebuilt on every load, never hand-edited — consistent with §3a’s “consumer profiles are generated, never hand-edited.” It is an ABox+TBox closure graph (entailing instance types and relations), distinct from the §3a opda-inference.ttl classes-alone TBox projection — see R6.

R5 — RDF 1.2: adopted in full, on a Jena toolchain

ODR-0002 pins RDF 1.2. This ODR realises that pin in full: opda adopts the RDF 1.2 reification vocabulary (rdf:Reifier, rdf:reifies), the triple-term concrete syntax <<( s p o )>> and annotation syntax {| … |} for statement-level annotation, and SPARQL 1.2 query features. Statement-level annotation (provenance, confidence, attribution carried on a specific triple) uses RDF 1.2 triple terms — not an OWL-2 annotation-axiom (owl:annotatedSource/Property/Target) or reification work-around adopted to placate a parser.

The toolchain follows the standard, not the reverse. opda standardises on Apache Jena (riot for parse/serialise, jena-shacl for validation — ADR-0036), which reads and writes RDF 1.2 natively. opda does not take a dependency on a library that cannot parse RDF 1.2 — notably Python rdflib, which through its current (7.x) releases cannot parse triple-term syntax. Any opda step that today parses or serialises RDF via rdflib/pyshacl — the BASPI5 round-trip harness (ADR-0014), and any rdflib use inside opda-gen — migrates to Jena (ADR-0036). The principle: never let the weaker tool dictate the data model — adopting a standard and then retiring the part a chosen parser cannot read (e.g. downgrading triple-term syntax to OWL-2 annotation axioms / SSSOM to stay rdflib-parseable) is the anti-pattern opda avoids. A prior-art instance of that anti-pattern, and the corrective hand-off, are cited in §More Information.

SHACL 1.2 validation does not require RDF 1.2 data (the two are separable), but both ride the same Jena toolchain — so adopting Jena for one removes the only excuse for deferring the other.

R6 — Partial re-scope of ODR-0004 §3a: the opda-inference.ttl projection

ODR-0004 §3a defines a derived profile opda-inference.ttl = classes alone → OWL reasoners (HermiT / Pellet / Konclude TBox classification). That profile targets the full OWL DL classification this ODR places out of scope, and it was never built (opda-inference.md: “spec only; directory does not yet exist”). This ODR proposes to supersede the DL-classification intent of that §3a row: opda’s inference is the load-time OWL-RL-safe closure (R1/R4), not external DL reasoning.

Ratification (directing authority, 2026-06-01). This re-scope amends a council-ratified clause of ODR-0004. Disposition (a) supersede the DL-classification intent is adopted: opda does not run full OWL DL reasoners (HermiT/Pellet/Konclude); the load-time OWL-RL-safe closure (R1/R4) is opda’s only inference. ODR-0004 §3a and docs/manual/physical-database/derived-profiles/opda-inference.md are amended accordingly (the opda-inference.ttl row is re-pointed from “DL-reasoner input” to “the OWL-RL-safe closure / a classes-alone export retained only as an optional artefact for third-party DL tooling, never built by opda’s pipeline”). Dispositions (b) retain-as-optional-export and (c) re-scope-the-name are folded into (a): the name is retained, the intent superseded.

R7 — Interaction with the BASPI5 round-trip and the EPCCertificate defect

opda’s declared closure is narrower than the inference="rdfs" setting the round-trip currently passes to pyshacl (ADR-0014): the Safe Group excludes rdfs:domain/range entailment (R2). Consequently:

• Under opda’s regime, an opda:EPCCertificate carrying opda:currentEnergyRating (whose rdfs:domain is opda:Property) is not inferred to be a Property. The known EPCCertificate defect (handover 2026-06-01 §8) does not manifest in the R1 closure.
• The defect manifests only under the broader inference="rdfs" validator setting. ADR-0036 MUST therefore align the validator’s entailment with the R1 closure — validate against the materialised R1 graph, not an ad-hoc full-RDFS inference. The underlying emitter mismatch (a Property-domain predicate bound on a non-Property subject) SHOULD still be fixed at source (ADR-0035), but it ceases to be a correctness landmine once domain entailment is excluded.