Controlled Side Effects

Kind: principle

Layer: Atomic Boundary

Record: architecture:controlled-side-effects

Severity: recommended

Scope: function, module, boundary

Canonical: Ontology

A design rule that mutation, I/O and persistence happen at declared boundaries, around a core of pure functions.

Listed in Architecture principles, after State Isolation and before Petri Nets.

Requires

• Effect Boundaries

Reinforces

• Predictability
• Testability

Enables

• Pure Core / Imperative Shell

Conflicts with

• Action at a Distance
• Hidden Side Effect

In tension with

• Performance Optimization

Tensions

• Controlled Side Effects / Performance Optimization

Contracts

• Execution Core

Violated by

• Hidden Side Effect

Refactored by

• Make Effects Explicit
• Separate Query from Command

Severity

• recommended

Category

• Transactions / State / Concurrency

Linked from

• Anti-patterns
• Correctness / Determinism / Verification
• Core Modular Design
• Correctness / Determinism / Verification
• Transactions / State / Concurrency
• Architectural Clusters
• Severity levels
• The resolutions