tegwick
50c68575f1
Assistant: codex Assistant-Model: gpt-6-astra Assistant-Session: 01a0cffe-206f-7323-89d3-b20ca4cf4bf9
38 lines
1.8 KiB
Markdown
38 lines
1.8 KiB
Markdown
---
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title: Derived State
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status: draft
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maturity: hypothesis
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families: [projection, affordance]
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scales: [L3, L6]
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admission: research-candidate-only
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---
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# Derived State
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Context: totals, filters and enabled states can be calculated from existing inputs.
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Keeping separate mutable copies risks disagreement; repeated computation costs time.
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Proposed solution: identify the authoritative inputs and derive a read-only result
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from a coherent input snapshot. Cache expensive results only with explicit dependency
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and invalidation rules. An independently editable proposal is a new input, not a
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computed value to overwrite when its source changes.
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Result: fewer mutable synchronization obligations, at the cost of computation and
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cache bookkeeping. Deriving from stale input does not make the output fresh. Time,
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locale and access context must be represented when they influence the result.
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Evidence: B02 locates Redux selector guidance. This is a documented mechanism,
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not a requirement to adopt Redux or a global store. Alternative: a maintained
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materialized view when recomputation is too expensive, with its consistency contract.
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Historical snapshots and user overrides must retain their distinct meanings.
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Proposed relations: supplies [Presentation Model](PresentationModel.md); refreshing
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inputs through [Invalidate and Reproject](InvalidateAndReproject.md) is conditional.
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Next test: change a filtered record and its filter together; verify list and total
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use the same snapshot, then challenge a cached result with a changed locale.
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Evidence locators: [breadth review](../reviews/PatternBreadthExpansion.md).
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All relations are research proposals; no canonical identity or admitted graph edges.
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The next test is planned, not executed. Known uses of the complete proposed contract
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have not been verified in this investigation.
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