> For the complete documentation index, see [llms.txt](https://eurekabusiness.caiziii.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://eurekabusiness.caiziii.com/eurekabusinesscommunity-en/module-reference/core-module.md).

# Core Module Contracts

Core forms the architectural foundation of EurekaBusiness, offering domain-neutral contracts for Retail, Restaurant, and downstream addons.

## Primary Public APIs

| API                                 | Purpose                                                        |
| ----------------------------------- | -------------------------------------------------------------- |
| `QualifiedTypeId`                   | Immutable namespaced identifier used across modules            |
| `ElementDefinition`                 | Immutable descriptor of a registered element                   |
| `ElementRegistrar`                  | Bootstrap registrar for element definitions                    |
| `ElementView`                       | Frozen, read-only query view of active elements                |
| `CustomerVariantRegistrar`          | Bootstrap registrar for customer appearance and AI variants    |
| `CustomerVariantDefinition`         | Immutable definition of a customer variant                     |
| `ElementRarityAlgorithm`            | Base class for rarity evaluation against shop element profiles |
| `CustomerContinuePurchaseAlgorithm` | Contract deciding continuous purchasing appetite               |
| `ElementContinuePurchaseAlgorithm`  | Element-driven continuous purchase evaluation base             |

## Element Definitions

Elements declare a qualified ID, translation key, 16×16 icon asset, and an optional `0xRRGGBB` tint color. Elements contain no pricing or item associations; domain modules assign elements and levels (`1..9`) to catalog items.

## Frozen Read-Only Views

Following the bootstrap phase, Core freezes all registries into immutable views. Runtime components query these read-only views and discard mutable registrar references.

## Dependency Boundaries

Addons must depend only on exported API contracts. Never import `internal` packages or access private fields via reflection.


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