Robustness Principle

Kind: principle

Layer: Correctness Core

Aliases: Postel's Law

Record: architecture:robustness-principle

Severity: contextual

Scope: protocol, API, input processing

Canonical: Ontology

A design rule that a component is strict in what it sends and tolerant of harmless variation in what it receives.

Listed in Architecture principles, after Resilience and before Error Handling.

Requires

• Strict Output
• Tolerant Input

Reinforces

• Compatibility

Enables

• Interoperability

Conflicts with

• Fragile Parsing

In tension with

• Strict Validation

Tensions

• Robustness Principle / Strict Validation

Violated by

• Fragile Parsing

Refactored by

• Canonicalization
• Invariant Check

Severity

• contextual

Category

• Error Handling / Resilience

Linked from

• Contracts / Interfaces / Compatibility
• Core Vocabulary
• Correctness / Determinism / Verification
• Error Handling / Resilience
• Severity levels
• The resolutions