# 1. Mental Model

Before any worked example, the conceptual map.

The framework is module-driven: every screen a PM creates and every screen
a customer sees is a row in `gdsmodule` joined to layout rows in
`gdsconfigformmaster/slave`, permission rows in `gdsjurisdiction`, and
stored procedures invoked through `BusinessBaseController` in the runtime.

These pages are intentionally short — each one explains one concept, with
links to the [vertical slices](../slices/index.md) that exercise it.
Concepts pages should stay short; if one grows past a screenful, that's
a sign the content wants to be a slice instead.

- [The data-driven thesis](thesis.md) — *why* the framework looks the way it does.
- [Modules, forms, virtual tables](modules-forms-vtables.md) — the three core nouns.
- [Master / slave document pattern](master-slave.md) — header/lines, everywhere.
- [No-FK, semantic-FK reality](semantic-fk.md) — how relations actually work.
- [Two customization channels](customization-channels.md) — metadata edits vs. SQL scripts.
- [Customization layers](customization-layers.md) — within Channel 1, how base / per-tenant / per-user overlays merge.
- [Multi-tenancy and product editions](multi-tenancy.md) — the three scoping axes (`sBrandsId`, `sSubsidiaryId`, `sVersionFlowId`).
- [The metadata-driven request lifecycle](request-lifecycle.md) — the diagram you'll come back to.
- [The three API tiers](api-surface.md) — internal (`xlyEntry`), external (`xlyApi`), inbound webhooks (`xlyInterface`).