Create technology_overview.md

Author: oblomov-dev

docs/advanced/technical/technology_overview.md

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+## Technology Overview
+
+### abap2UI5: Over-the-Wire for SAP (2023+)
+abap2UI5 applies the Over-the-Wire principle to SAP UI5 apps. The backend (ABAP) defines UI5 XML Views and ViewModels, which are sent to the browser. A generic, static UI5 app dynamically renders this content.
+
+- **Frontend stays generic & static**
+- **No custom JavaScript development needed**
+- Perfect for CRUD-heavy business applications
+- Inspired by modern Over-the-Wire frameworks like Hotwire, Livewire
+- Addresses SAP's "Clean Core" approach by keeping custom code backend-driven
+
+### RAP / Fiori Elements: Backend-driven SPA (2019+)
+The **RESTful Application Programming Model (RAP)** standardizes how SAP applications expose data and services via OData V4. **Fiori Elements** apps use these services to render UIs client-side in the browser.
+
+- Developers define CDS Annotations in ABAP
+- UI is built dynamically by the UI5 Fiori Elements runtime (SPA)
+- Suitable for standard apps with CRUD patterns
+- Reduces custom UI development, but still SPA complexity (OData Metadata handling, UI5 runtime)
+
+### UI5 Freestyle: Custom SPA (2010+)
+UI5 Freestyle apps offer full control over the frontend. Developers build custom UI5 applications using JavaScript, XML Views, and UI5 Controls.
+
+- Allows highly customized, interactive UIs
+- Full SPA architecture in the browser
+- Requires frontend expertise (JavaScript, UI5 skills)
+- More flexible, but also more complex in development & maintenance
+
+### Web Dynpro ABAP: Server-Side Rendering (2003+)
+Web Dynpro ABAP is SAP's traditional web UI framework. It renders HTML on the server and sends complete pages to the browser for each interaction.
+
+- Component-based UI framework fully implemented in ABAP
+- Classic Server-Side Rendering paradigm (SSR)
+- Suitable for transactional SAP applications
+- Limited flexibility for modern UI patterns, but robust and widely used
+
+### ITS Mobile: Legacy SSR for Mobile Devices (2000+)
+**Internet Transaction Server (ITS) Mobile** converts classical SAP Dynpro (SAP GUI) screens into HTML pages for mobile browsers.
+
+- Simplifies legacy app mobilization (e.g., warehouse scanners)
+- Pure server-side HTML rendering (SSR)
+- Very basic UI, optimized for keyboard-based navigation
+- Still relevant for niche use cases with rugged devices
+