Minor changes in Section 8.4

For better readability and completeness:

From "...the passive structure elements (business objects) that are manipulated by behavior..." to "...the passive structure elements (business objects) that are manipulated by internal business behavior..."

Add this note after Figure 64:

"Note: This figure does not show all permitted relationships; every element in the language can have composition, aggregation, and specialization relationships with elements of the same type. Furthermore, there are indirect relationships that can be derived, as explained in Section 5.7. The full specification of permitted relationships can be found in Appendix B."