Why such a data model?

• Relational/deductive databases imposes 1-NF. Efficient to implement, but...

  
  
  

  => difficult to map external data sources into 1-NF, and tends to split objects into hundreds of pieces.
  
  
  

• Many programming languages such as C, SML, etc. insist on creating new types and do not allow ``free-forming'' type constructors. Rich, but...

  
  
  

  => not suitable for database queries because

  • almost every query results in a ``new'' type
  • some input/output schemas take pages to write down