CUSTOMER(cnumber, first-name, last-name) 
PRIMARY KEY = (cnumber)

ORDERS(onumber, odate, cnumber) PRIMARY KEY = (onumber)
FOREIGN KEY = (cnumber) REFERENCES CUSTOMER(cnumber)

LINE(onumber, lnumber, item, price, total)
PRIMARY KEY = (onumber, lnumber)
FOREIGN KEY = (onumber) REFERENCES ORDERS(onumber)

DOCUMENT(title, class, edate)

ACCESS(user,class)

SELECT title
FROM DOCUMENT JOIN ACCESS
              ON DOCUMENT.class = ACCESS.class
WHERE user = ...;

class Document{ String title;
                String className;
                Date edate )

	  
class Access( String user,
              String className)

for(a in Access)
      for( d in Document)
             if a.user = ... and d.className = a.className then
                 out(d.title);