Minor changes in Section 4.1.2
For better readability, some small bhanges are proposed:
From "An internal behavior element represents a unit of activity that can be performed by one or more active structure elements." to "An internal behavior element represents a unit of activity that can be performed by one or more _internal _active structure elements."
From "An event represents a state change" to "An event represents something that happens or occurs, especially something significant or noteworthy; e.g. a state change."
From "...moments at which the event happens" to "... moments at which the event occurs, as well as an attribute to indicate its frequency"
Add after Figure 10: "Behavior elements are denoted using boxes with round corners and an icon in the upper-right corner, or by the icon on its own."