docs: Clarify OSM Notes ecosystem relationships in Rationale.md

- Updated descriptions for OSM-Notes-Viewer and OSM-Notes-Ingestion to reflect their roles within the ecosystem.
- Enhanced the note on JSON exports to specify the relationship with OSM-Notes-Data.
- Improved references section to include a link to OSM-Notes-Data and provide a complete overview of the ecosystem.

Author: angoca

docs/Rationale.md

@@ -269,8 +269,8 @@ Once the data warehouse is populated, the system provides:
 4. **JSON Export**: Validated JSON files for OSM-Notes-Viewer (sister project)
 5. **API-Ready Data**: Structured data ready for web APIs
 
-**Note**: The JSON exports are consumed by the OSM-Notes-Viewer sister project, which provides the
-web interface for visualizing these analytics.
+**Note**: The JSON exports are consumed by OSM-Notes-Viewer (part of the 8-project ecosystem), which provides the
+web interface for visualizing these analytics. Viewer consumes data from OSM-Notes-Data (GitHub Pages), which is populated by Analytics export scripts.
 
 ## Relationship to Other Projects
 
@@ -290,19 +290,19 @@ OSM-Notes/
 └── OSM-Notes-Data/          # JSON data files (GitHub Pages)
 ```
 
-### OSM-Notes-Ingestion (Sister Project - Upstream)
+### OSM-Notes-Ingestion (Base Project - Upstream)
 
 - **Purpose**: Collects and stores raw note data from OSM
 - **Relationship**: Analytics reads from ingestion base tables
-- **Dependency**: Analytics requires ingestion to run first
-- **Level**: Sister project at same organizational level
+- **Dependency**: Analytics requires ingestion to run first (Ingestion is the base project)
+- **Role**: Base project - first created, foundation for all others
 
-### OSM-Notes-Viewer (Sister Project - Downstream)
+### OSM-Notes-Viewer (Ecosystem Project - Downstream)
 
 - **Purpose**: Web interface (web page) for visualizing analytics
-- **Relationship**: Viewer reads JSON exports from analytics
-- **Dependency**: Viewer requires analytics to generate JSON files
-- **Level**: Sister project at same organizational level
+- **Relationship**: Viewer consumes JSON files from OSM-Notes-Data (GitHub Pages), which is populated by Analytics export scripts
+- **Dependency**: Viewer requires OSM-Notes-Data (which is generated by Analytics)
+- **Data Flow**: Analytics → Data → Viewer
 - **Technology**: Web application (HTML/CSS/JavaScript)
 
 ### OSM-Notes-Common (Shared Library)
@@ -348,10 +348,11 @@ techniques, the project provides a scalable, maintainable solution for OSM Notes
 
 ## References
 
-- [OSM-Notes-Ingestion](https://github.com/OSM-Notes/OSM-Notes-Ingestion) - Sister project
-  (upstream)
-- [OSM-Notes-Viewer](https://github.com/OSM-Notes/OSM-Notes-Viewer) - Sister project (downstream)
+- [OSM-Notes-Ingestion](https://github.com/OSM-Notes/OSM-Notes-Ingestion) - Base project (upstream)
+- [OSM-Notes-Viewer](https://github.com/OSM-Notes/OSM-Notes-Viewer) - Ecosystem project (downstream, consumes Data)
+- [OSM-Notes-Data](https://github.com/OSM-Notes/OSM-Notes-Data) - JSON data files (populated by Analytics)
 - [OSM-Notes-Common](https://github.com/OSM-Notes/OSM-Notes-Common) - Shared library (Git submodule)
+- See [Main README](../README.md) for complete ecosystem overview (8 projects)
 - [DWH Star Schema ERD](DWH_Star_Schema_ERD.md) - Data warehouse design
 - [ETL Enhanced Features](ETL_Enhanced_Features.md) - ETL capabilities
 - [Main README](../README.md) - Project overview