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Unit 2: Text

the Hierarchical structure notes
The hierarchy is by far the most important structure because it is the basis of almost all websites
and most other hypertexts as well. Why is this so? Because hierarchies are orderly (so users can
grasp them) and yet they provide ample navigational freedom. The node-link diagram in Figure
2.1 shows the orderly nature of hierarchies. Users start at the home page, descend the branch that
most interests them, and make further choices as the branch divides. At each level, the information
on the nodes becomes more specific. Notice that branches may also converge.
The flexibility of the hierarchical structure is apparent in the more richly linked hierarchy shown
in Figure 2.2. Here the basic hierarchical structure (the primary links shown as solid lines) is
supplemented by secondary links (shown as dotted lines). The secondary links function mainly
as shortcuts; they let users jump around more freely. For example, users can move laterally
along the sibling nodes of a single branch and can jump from one branch to another, without
having to first move up to a higher-level node. Although not shown in the figure, there is almost
always a link from every node back to the home page (the top of the hierarchy) and other kinds
of upward links.

figure 2.2: a node-link Diagram of a Website and a Mock-up of one
of the pages in this Website

Especially when designing larger hypertexts, designers must choose between making the hierarchy
wider (putting more nodes on each level) or deeper (adding more levels). One well-established
design principle is that users more easily navigate a wide hierarchy (in which nodes have as many
as 32 links to their child nodes) than a deep hierarchy.
You may have recognized that a great many print documents are hierarchies in one significant
respect. They are often divided into hierarchical divisions like parts, chapters, sections and
subsections. These divisions create a logical hierarchy that the user encounters while reading
linearly. Cross references in print invite the reader to jump from one part of the document to
another and so are analogous to links in hypertext.

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