Architecture

Structural soundness. Layer purity respected, composition pattern declared, dependency direction correct, no cross-layer violations.

Architecture defines the structural boundaries, layer constraints, and composition rules that govern how system components interact. In SBX, the four-layer FDD model (PD, MD, SI, UI) enforces strict separation of concerns — specifications live in PD, domain types in MD, adapters in SI, and entry points in UI. Architecture decisions are captured as immutable records that constrain all subsequent implementation.

PD

Pure function, no side effects, composes via pipeline

MD

Effectful, db-only effects, repository pattern, algebra-interpreter

SI

Effectful, net+db effects, handler composes md functions

UI

Mixed — pure presenters + effectful handlers

• FDD1 Develop Overall Model

• Three-map entity architecture Decision 0019 — Entity Structural Model