ADR A-07b: Minimal Instrument shape and versioning contract

Status

Accepted

Context

Behaviour depends on a stable target model for writing effects into document structure, and Party already forward-references an Instrument-side relation for obligation fulfilment. Instrument is currently empty, so a minimal, law-coherent shape is required before Behaviour authoring.

Decision

Instrument defines the smallest required substrate-facing model:

• Classes: ins:Element, ins:Provision, ins:Obligation, ins:Qualifier.
• ins:Element subclasses fnd:Version.
• ins:Provision, ins:Obligation, and ins:Qualifier subclass ins:Element.
• ins:Provision, ins:Obligation, and ins:Qualifier are mutually disjoint. ins:Element is their common superclass, so it is not in the disjointness axiom (corrected 2026-09-25: including it made every subclass unsatisfiable, fixed in 9a12da4).
• Cross-reference properties include:
  • ins:hasProvision / ins:partOfInstrument
  • ins:hasObligation / ins:inProvision
  • ins:hasQualifier / ins:qualifies
  • ins:fulfilledBy (to Party participation structures)

Versioning contract (R-B7):

• Instrument nodes are never updated in place.
• Any material change creates a new fnd:Version individual with the same fnd:hasIdentity and links the old version to the new one via fnd:supersededBy.
• Supersession is only legal between versions sharing the same identity.

Consequences

• Behaviour can target a concrete minimal document model in Gate 3.
• Party forward references to obligation fulfilment are now grounded by a declared Instrument property.
• Instrument remains minimal and domain-neutral while preserving version-safe mutation semantics.