Hamish Burke | 2025-03-08
Related to: #databases
Three Schema Architecture
Allows for physical data independence
External level
- Can have multiple of these (for different end users)
- They all map to the conceptual schema
Conceptual Level
- Maps to internal schema
- Perspective of the DBMS
- Changes to this shouldn't affect the external schema
Internal Level
- Describes physical storage setup
- Hashing/pointers to access data etc
- Changes to this should have no implications to the conceptual layer
- This allows physical optimisation/tuning