# ADR 000: Temporal platform layers

- HTML version: https://robbiepalmer.me/projects/personal-engineering-platform/adrs/000-temporal-platform-layers
- Project: Personal Engineering Platform (https://robbiepalmer.me/projects/personal-engineering-platform.md)
- Status: Accepted
- Date: 2026-09-12
- Initiatives: Semi-autonomous Software Development (https://robbiepalmer.me/initiatives/semi-autonomous-software-development.md)

## Context

Shared ADR stubs made project histories read like dependency manifests and
could not preserve which default applied before a project was completed.
The Personal Knowledge Graph stores and renders these records, but that
representation does not own the policies recorded here.

## Decision

Own shared defaults in this project. Record slot policy, technology selection,
and project adoption as separate dated records with half-open UTC periods.
Projects explicitly adopt each independent layer they use and keep local ADRs
for their own choices and overrides.

This project owns the layer and slot definitions, their default selections,
and the contract for a project's dated adoption. The Personal Knowledge Graph
owns loading, validating, querying, and rendering those records.

## Consequences

Queries can explain an effective stack and keep completed projects fixed. The
temporal records remain available to those queries, while reader-facing graph
views present direct project-to-layer and layer-to-technology relationships.

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