AGGREGATION HIERARCHIES

• IF AN ATTRIBUTE OF CLASS A IS AN OBJECT OF CLASS A' - A IS BEING AGGREGATED FROM CLASSES SUCH AS A'
  
  
  • AN AGGREGATION RELATIONSHIP EXISTS BETWEEN A & A'
  
  
• THIS CAN BE REPEATED AT SEVERAL LEVELS ESTABLISHING AGGREGATION HIERARCHIES AMONG SOME OF THE CLASSES IN THE SCHEMA
  
• AGGREGATION HIERARCHIES ARE CRUCIAL FOR REPRESENTING BUILT ENVIRONMENT & OTHER ENGINEERING STRUCTURES