Please, in a few lines, walk me through the steps of Donald Norman's interaction model.

What conjures up in your thoughts when you think of an email? What factors into the length of time it takes to send an email from one place to another? Keep a diary to jog your memory of significant events and details. Where do they diverge from one another? Do you know the level of detail (or abstractness) that each model has?

What are the paradigm's enhancements?

In the context of human-computer interaction, what do you mean when you talk about a shift in paradigm?