Extend the explanation of the Top-Level Language Structure (Section 3.2)

The top-level language structure explanation should include the top-level relationship types:

• A model is a collection of concepts – a concept is either an element or a relationship

• An element is either a behavior element, a structure element, a motivation element, or a composite element

• A relationship is either a structural relationship, a dependency relationship, a dynamic relationship, or an other relationship

Figure 1 would become something like this: