lattice of kernel classes

[Sonya E. Keene <skeene@STONY-BROOK.SCRC.Symbolics.COM>]

Three comments on this section of MOP:

1.  In the diagram, there is a class named "standard-structure".   I
think it is meant to be "structure-object"; which is what it is called
in the previous section. 

2.  The classes <structure-object> and <standard-object> have angle
brackets around them, which indicates that they are used primarily for
type determination, like <class>, <method>, and so on.   I don't think
of those two classes in that way; I think of them as primarily being
there to support default behavior of instances of structure-class and
standard-class.    So, I would recommend getting rid of the angle
brackets.

3.  This section states that T is an instance of built-in class, but the
section "Instances of class, built-in-class, and structure-class" states
that an implementation can use standard-class for ANY class associated
with a Common Lisp type.   This seems contradictory.