8.7 Cross-Plane Relationships

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Cross-plane relationships occur when an event, decision, message, record, or action in one Runtime Plane affects, references, constrains, or produces information in another Runtime Plane.

The Financial Systems Archetype separates Runtime Planes to preserve architectural clarity. That separation does not mean the planes operate in isolation. A Financial System often requires interactions across planes, but those interactions need to remain explicit, Traceable, and governed.

For example, a health event in the Health and Observability Plane may trigger a recovery command in the Control Plane. A Data Plane event may require a policy decision in the Policy and Release Plane before information leaves an internal environment. A Policy and Release Plane decision may generate an audit record in the Audit and Provenance Plane. A Control Plane replay command may cause a Node to republish Data Plane information from preserved Evidence or persisted records. Cross-plane relationships must not collapse the planes into one another. The architectural purpose of each plane remains distinct even when information flows between planes.

A cross-plane relationship can identify:

Originating Runtime PlaneReceiving or affected Runtime PlaneEvent, message, decision, or record causing the relationshipNode or Node Role participating in the relationshipCommunication Endpoint or mechanism involvedData Structure Definition governing the exchanged information, where applicableThe policy, rule, or condition authorising the relationship, where applicableTraceability and Evidence record supporting later reviewExamples of cross-plane relationships appear in Table 8.7-1.

Table 8.7-1: Examples of cross-plane relationships among Runtime Planes

Originating plane	Affected plane	Example
Health and Observability Plane	Control Plane	A degraded Node status triggers a restart, retry, or recovery command.
Data Plane	Policy and Release Plane	A transaction result requires an evaluation for release before an external consumer receives it.
Policy and Release Plane	Audit and Provenance Plane	A release decision creates an audit and provenance record.
Control Plane	Data Plane	A replay command causes selected Data Plane records to be republished.
Data Plane	Audit and Provenance Plane	An analytical assertion creates provenance that links inputs, producing a Node, model version, and output.

Cross-plane relationships support operational coordination, governed release, auditability, replay, recovery, and Evidence. They also help reviewers understand how the system behaves without losing the separation between runtime concerns.