SPMS13 — Allow PatternSection:body to refer to more than a simple string

The PatternSection class currently only allows a simple string for the body attribute. It would be much more useful if it were to allow any MOF::Element based entity to represent the body. This would allow for not only richer text, but also diagrams, a remote URI (as a structured URI, not just a string), or other expression.

Note that the image in Figure 8.1 and the XMI file in SPMS 1.2 were both correct, this only affects the prose in Section 8.5.