Conclusion
  - Annotations can be treated as RDF metadata
-  The reuse of current Web standards makes the implementation relatively
    easy
- Open infrastructure 
    
      - RDF schema for defining annotation properties
- XPointer for associating annotations to any XML document
- XLink for presentation
- HTTP for data exchanges
 
- Easy to extend (discussion threads)
- Client independent
- Some obstacles remain
    Scalability issues... Robust annotations