Forward Compatibility

Kind: constraint

Layer: Contracts Core

Aliases: Unknown Field Handling

Record: architecture:forward-compatibility

Severity: recommended

Scope: API, schema, protocol

Canonical: Ontology

A rule or precondition that an older reader accepts data from a newer writer by ignoring the fields it does not know rather than failing on them.

Listed in Architecture principles, after Backward Compatibility and before Versioning.

Requires

• Extensible Schema

Reinforces

• Evolutionary Architecture

Enables

• Rolling Upgrades

Conflicts with

• Strict Fragile Parsers

In tension with

• Strong Validation

Tensions

• Forward Compatibility / Strong Validation

Violated by

• Strict Fragile Parsers

Refactored by

• Extension Points
• Tolerant Reader

Severity

• recommended

Category

• Contracts / Interfaces / Compatibility

Linked from

• Architecture Review / Evolution / Governance Artifacts
• Contracts / Interfaces / Compatibility
• Severity levels
• The resolutions