Screen Areas for Hypertexts
The Site Map & Title Area is static and has no scroll bar. It contains an explicit representation of the site structure as conceived by the designer The title and picture of the book's cover do not scroll away as you navigate to any major element (chapter), thus context is not lost.
This Site Map is the book's table of contents (TOC), which is how the author conceived its structure.
When you click on a chapter it appears in the Content Area.
The Entry Point Area is reserved for links other than those related to the explicit structure.
It links to content based on how the site is used by human beings from a mostly semantic perspective.
Entry points are determined by observing and analyzing how people use the document and make associations between its words and the larger context.
The clues of usage for a printed work are usually pretty obvious:
dog-eared pagessticky notes or other papers hanging out of the book
dirty binding (because of frequent use)
folded pages
highlights
scribbles
and the like.
Entry Points represent implicit structures and semantic encoding of the document from the reader's point of view and typically serve 80% of users as they perform typical tasks.
Entry points can be independent of or dependent on the site Map. The choice is based on how much intra-document navigation (versus inTER-document navigation) is required and how the structural elements of the site Map must be augmented by semantic clues for the site to be usable.
In the Dilbert example the entry points are independent of the site Map.
We might have analyzed each chapter for implicit structure and presented a separate set of entry points for each one. The user would be presented with a different set of entry points each time a different chapter was selected from the TOC, thus forming a hierarchical browser - another useful but often abused wayfinder.
