ADR-A91: Eligibility candidate evidence binding

Status: Accepted Date: 2026-09-25 (proposed), 2026-09-25 (accepted) Related: ADR-A01 (layer dependency order), ADR-A17 (unified projection authoring), ADR-A24, ADR-A89, ADR-A90 Unit: applied-ontology-readiness

Context

Every Eligibility backend reads a candidate from an elg:Question (elg:candidateRangeSet, elg:candidateValue). An applied ontology keeps its facts on its own properties: an employee’s job family, a patient’s diagnosis and weight, a loan’s credit score. To evaluate a condition today it must copy each fact into a question first. The copy duplicates state, detaches the decision from the fact it was based on, and has to be kept in step by code outside the graph.

The mork-eligibility-compiler sketch identified this gap and deferred an “executable projection contract” layer pending an ADR. Surface already reads domain data through declared paths (srf:PathStep, an indexed step list chosen because it canonicalises and hashes directly), but Surface does not import Eligibility and sits outside the ADR-A01 chain.

Options

Decision

Option A, with D remaining available.

1. Eligibility adds elg:EvidenceBinding, relating one condition to the subject class whose instances it evaluates and to an ordered list of elg:EvidenceStep (property, direction, index), shaped like srf:PathStep so a later lift to Foundation needs no data change.
2. The terminal value is a skos:Concept for concept conditions and a qnt:Quantity for interval conditions. A literal terminal value is read on a value space the binding names.
3. Questions and decisions produced through a binding name their subject with a new elg:aboutSubject. elg:subjectRoleOccupancy keeps its meaning for party subjects.
4. The IR (ADR-A89) reads candidates through a binding when one exists and from the question otherwise. Every backend, including the OWL backend of ADR-A90, uses the same binding.

Consequences

• An applied ontology evaluates conditions directly over its own data, with decisions linked to the subject and, through provenance, to the facts read.
• Eligibility takes a MINOR bump with the ADR-A86 cascade.
• The step-list pattern is duplicated between Eligibility and Surface. ADR-A92 records the Foundation lift as a candidate for the same Foundation change that introduces the derived-artefact contract.
• Alternation and zero-or-more paths stay out of scope, as for Surface.

Implementation notes (2026-09-25, applied-ontology-readiness AOR-9)

• The compiled artefacts key their rows and shape reports by the subject itself and mint no question or decision record. elg:aboutSubject (item 3) therefore has no producer yet and is not declared.
• Subjects are the instances of the subject class and of its subclasses, as a SHACL sh:targetClass selects them.
• SWRL records a bound outcome per condition with exe:permittedUnder and exe:deniedUnder, since exe:impliesDecision on a subject would not say which condition decided it. A bound interval rule reads one terminal form: a literal where the binding names elg:readOnSpace, else a qnt:Quantity.
• SWRL rules are DL-safe, so under a reasoner their variables bind only named individuals. A path through a blank node (an anonymous role, say) derives nothing, while SPARQL and SHACL still read it. Name intermediate nodes where SWRL must reach them.