ITPElement represents a general element in the tree. It is aware of its element type, which will be different for each descendant of ITPElement.
ITPElement holds an info structure, which basically is a JSON collection of information about the particular element. The structure and contents of this collection correspond trivially to the node sets that are passed back and forth between the templates in the Xslt. Refer to paragraph Passing information and Appendix C for more information.
ITPElement is aware of the hierarchical relations between the objects. It contains a reference to a parent object and to an array of children. It knows how to transfer messages through the system and how to find an element in its subtree.
ITPElement defines the general initialization of an element, which may be asynchronous. The most important part of initialization is the construction of a map of screen elements. At this point the JavaScript may manipulate the content of the screen.