Information Locality¶
Core Idea¶
Information Locality is the placement principle that responsibility for a decision, guarantee, or interpretation belongs at a level that possesses the information needed to discharge it. A less-informed layer may filter, accelerate, recommend, or catch some failures, but it cannot own correctness when decisive context remains elsewhere. The principle is about criterion–information fit, not a blanket preference for physical nearness, decentralization, or low latency.
Broad Use¶
- Computer systems: endpoint-defined guarantees remain at endpoints; application semantics remain where application context is visible.
- Organizations: operational authority moves toward people who can observe changing local conditions, while central policy supplies boundaries and shared goals.
- Medicine: a decision requiring bedside signs and patient preferences cannot be fully discharged by a remote rule using summary data alone.
- Law and governance: responsibility for a judgment belongs where the relevant record, authority, and purpose can be considered together.
- Engineering and safety: a component-level check can assist but cannot certify a system-level property that depends on interactions it cannot observe.
Clarity¶
The prime separates the owner of correctness from helpers. An intermediate check may be useful and even highly reliable, yet still lack evidence needed to close the criterion. Conversely, the best-informed location may be expensive or slow, so other levels can perform provisional work without inheriting final responsibility.
Manages Complexity¶
Placement disputes reduce to five questions: what exact criterion must be discharged, what information is necessary, where that information exists, which candidate owner lacks part of it, and what auxiliary work can safely happen elsewhere. This prevents architectural slogans from substituting for an information map.
Abstract Reasoning¶
Use the information-deletion test. For each candidate owner, remove every fact it cannot observe and ask whether two states now look identical even though the correct decision differs. If so, that location cannot own the criterion. It may still optimize common cases, but a better-informed level must verify or override it.
Knowledge Transfer¶
The roles travel unchanged: a criterion, its required information, several candidate owners with unequal views, a placement decision, and a gap that only an informed owner can close. Endpoints and routers can be replaced by field teams and headquarters, clinicians and administrators, or components and system integrators without changing the reasoning.
Example¶
A network relay can verify that each packet passed a local checksum, but it cannot know whether the complete application message arrived in the required order and matches the application's intent. Relay checks may improve performance, yet the application endpoint must still own the end-to-end guarantee because the decisive information lives there.
Relationships to Other Abstractions¶
Current abstraction Information Locality Prime
Parents (1) — more general patterns this builds on
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Information Locality presupposes Asymmetry Prime
Information Locality becomes discriminating only when candidate owners differ in access to information material to the criterion they might own.
Children (2) — more specific cases that build on this
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Plan-Execute Gap Domain-specific presupposes Information Locality
Plan-execute gap presupposes that execution holds criterion-relevant constraint information the planning level lacks.
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End-to-End Principle Domain-specific is a decomposition of Information Locality
End-to-End Principle is the framed or domain-specific realization of Information Locality; removing the local frame leaves the parent's structural relation intact.
Hierarchy path (1) — routes to 1 parentless root
- Information Locality → Asymmetry
Not to Be Confused With¶
- Locality of Reference: clustering of accesses in time or space, which supports caching and prediction.
- Information Asymmetry: a condition of unequal knowledge between parties; Information Locality is a responsibility-placement rule derived from criterion-relevant differences in access.
- Decentralization: authority may move inward, outward, upward, or downward depending on where the required information exists.
- Defense in Depth: redundant safeguards at multiple levels can coexist with one level retaining final ownership of a guarantee.
- Separation of Concerns: modular responsibility is broader; Information Locality selects an owner through access to decisive information.
Notes¶
Authored when the End-to-End Principle exposed a missing cross-domain parent. Queued for house-style harmonization and citation verification.