Categorie:ACCESS Wendy Mangue Nguema

2)

 In a total role constraints a frequent occurring requirement is that a role is mandatory to be played,chances are that in the underlying  
 universe of discourse there is a rule stating that each object should have an object type. The frequency constraint is used to constrain
 how many times a role may or must be played by objects from the associated object type.In short, the relation between the two constraints 
 is that a role is played at least once.

3)conceptual schema is called strongly identified if each admissible population is weakly identified.Thus it is impossible that a schema

 is strongly identified but not populable.