The OutSystems Architecture Canvas is a framework for designing scalable and maintainable application portfolios. It organizes application modules into three distinct, hierarchical layers. These layers are the Foundation layer, which contains reusable, non-functional services; the Core layer, which encapsulates the main business concepts and logic; and the End-User layer, which provides the user interfaces and screen logic. "Orchestrator" is not a named layer within this official three-layer framework. While orchestration logic exists within applications, it is a function performed within the layers, not a layer itself.

A. Foundation: This is incorrect because the Foundation layer is the bottom-most layer of the Architecture Canvas, providing reusable, non-functional building blocks.

C. End-User Layer: This is incorrect because the End-User layer is the top-most layer, containing the user interface and client-side logic for specific applications.

D. Core: This is incorrect because the Core layer is the middle layer, defining the application's core business concepts, data models, and business logic.

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1. OutSystems Official Documentation. "The 3 Layer Canvas". This document explicitly defines the framework: "The 3 Layer Canvas is a simple architecture framework that helps you design and organize your applications. It classifies modules into three distinct layers: Foundation

Core

End-User."

Source: https://success.outsystems.com/documentation/bestpractices/architecture/the3layercanvas/

2. OutSystems Official Documentation. "Designing the architecture of your OutSystems applications". In the section "The 3 Layer Canvas"

the document states: "The 3 Layer Canvas is an OutSystems architecture framework that organizes your application modules into three layers: Foundation

Core

End-User."

Source: https://success.outsystems.com/documentation/bestpractices/architecture/designingthearchitectureofyouroutsystemsapplications/

3. OutSystems Training. "Architecture Specialist" Guided Path

"Validating and Refactoring Applications" course. The course materials detail the purpose and composition of the three canonical layers of the Architecture Canvas: Foundation

Core

and End-User.

Source: https://www.outsystems.com/training/courses/127/validating-and-refactoring-applications/ (Section: Architecture Canvas)