Disclaimer The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.
One Sentence summary of the purpose of the UML Model:
1. Use Cases - "How will our system interact with the outside world?"2. Class Diagram - "What objects do we need? How will they be related?"3. Collaboration Diagram - "How will the object interact?"4. Sequence Diagram - "How will the objects interact?"5. State Diagram - "What stats should our objects be in?"6. Package Diagram -"Show are we going to modularise our development?"7. Component Diagram -"How will our software components be related?"8. Deployment Diagram -"How will the software be deployed?"