ADR-A97: MORK order relations in OWL 2 DL

Status: Accepted Date: 2026-09-25 Related: ADR-A83 (test-only reasoning engine isolation), ADR-A86 (ontology versioning) Unit: eligibility-compiler (A2, the Executable consistency check)

Context

mork:precedes, mork:softPrecedes and mork:refinesIntent were each declared transitive, asymmetric and irreflexive. OWL 2 DL allows asymmetry and irreflexivity only on simple properties, and a transitive property is never simple. So Mork was not OWL 2 DL: HermiT refused it, which blocked the reasoner check of Executable, which imports Mork.

Asymmetry and irreflexivity also fall short of what the relations mean. They catch a self-loop and a two-cycle, but not a longer cycle unless transitivity is applied too. The precedes scope note said SHACL enforced acyclicity, but no such shape existed. Only tools/mork’s Python checks tested it, and they cited a “Shape M7” that was never written.

refinesIntent was described as generating a preorder, which is reflexive, while being declared irreflexive.

Decision

1. The three relations stay transitive and lose asymmetry and irreflexivity. Mork is then OWL 2 DL, and consistent under HermiT.
2. Acyclicity is a SHACL-SPARQL constraint in ontology/mork/shapes/constraints.ttl, one shape per relation: mork:PrecedenceAcyclicityShape (M7), mork:SoftPrecedenceAcyclicityShape and mork:IntentRefinementAcyclicityShape. A transitive relation is irreflexive exactly when it is acyclic, so the same graphs are rejected as before.
3. Each shape follows the relation and the named properties it is derived from: precedes with resolvesIdentityFor and the inverses of compositeBroaderMapping, broaderApplicative, dependentMapping and templateMapping (Axioms P1, P2, P3, P10), and softPrecedes with the inverse of hypothesisMapping (P5). A cycle is found whether or not the relation has been materialised.
4. precedes and softPrecedes are checked separately, as declared. A cycle mixing hard and soft edges is not a violation.
5. refinesIntent is the strict refinement order. Its reflexive-transitive closure generates the preorder Int(I). Declaring it reflexive is not an option: owl:ReflexiveProperty is global, and local reflexivity (∃refinesIntent.Self) needs a simple property.

Consequences

• Mork 0.3.0 → 0.4.0, MINOR, together with the repair of five GCI axiom annotations the OWL API could not parse. Every graph that conformed before still conforms. The human accepted MINOR on 2026-09-25 since MORK has no consumers yet. The policy’s letter would call a new Violation shape MAJOR.
• A reasoner no longer reports a precedence cycle as an inconsistency. Running the shapes is the check.
• tools/test_mork_order_relations.py runs the shapes and checks Mork and Executable for consistency under HermiT.