Path Expressions

1. An expression of the form ``student.advisor.name'' is called a path-expression. References can be used to hide join operations and thus the use of references simplifies the query considerably.
2. Example.

    
   		 create table phd-students
   
   		 		 (advisor (ref(people))
   
   		 		 under people
   
   

    
   		 select phd-student.advisor.name
   
   		 from phd-students
   
   

3. In general, attributes used in a path expression can be a collection, such as a set or a multiset. E.g., to get names of all authors of documents, we have

    
   		 select Y.name
   
   		 from pdoc.author-list as Y