Not a bad idea though, the following relationship can be generated by the graphviz source below.

digraph { graph [pad="0.5", nodesep="0.5", ranksep="2"]; node [shape=plain] rankdir=LR; NormalUser [label=< <table border="0" cellborder="1" cellspacing="0"> <tr><td><i>NormalUser</i></td></tr> <tr><td port="1">facebookId</td></tr> <tr><td port="2">topic</td></tr> </table>>]; StaffUser [label=< <table border="0" cellborder="1" cellspacing="0"> <tr><td><i>StaffUser</i></td></tr> <tr><td port="2">managerId</td></tr> <tr><td port="3">permissions</td></tr> </table>>]; AbstractUser [label=< <table border="0" cellborder="1" cellspacing="0"> <tr><td><i>AbstractUser</i></td></tr> <tr><td port="a">firstName</td></tr> <tr><td port="b">lastName</td></tr> <tr><td port="c">birthdate</td></tr> <tr><td port="d">email</td></tr> <tr><td port="e">password</td></tr> </table>>]; NormalUser:1 -> AbstractUser:a; StaffUser:2 -> AbstractUser:a; }