Database Schema Designer

Design a complete database schema based on these requirements:

**Application Type:** {{APPLICATION_TYPE}}
**Core Entities:** {{CORE_ENTITIES}}
**Key Relationships:** {{KEY_RELATIONSHIPS}}
**Expected Data Volume:** {{DATA_VOLUME}}
**Database System:** {{DATABASE_SYSTEM}}

Please provide:
1. Entity-Relationship Diagram description
2. Complete CREATE TABLE statements with:
   - Primary keys
   - Foreign keys with appropriate ON DELETE/UPDATE actions
   - Constraints (NOT NULL, UNIQUE, CHECK)
   - Appropriate data types
3. Normalization analysis (ensure at least 3NF)
4. Index recommendations for common queries
5. Any denormalization suggestions for performance
6. Sample seed data INSERT statements