Description of the illustration dim_key.eps

dim_ref 
  [classification_clause]...
  KEY  
    {[(] [alias.] fact_column  [)] 
     |
     (  [alias.] fact_column [, [alias.] fact_column]... )
    }
  REFERENCES 
     { [DISTINCT]
       [(]  attribute  [)] 
       | 
       ( attribute [, attribute]... )
     }   
  HIERARCHIES ( hier_ref [, hier_ref]... )