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Semantic-Based Navigation in Open Spaces 277
simplicity, universal usage and perhaps the unavailability of complex navigation options,
which lessens information overload (i.e., the user is unlikely to get lost).
Figure 10-4. The linear reciprocal navigation model supports two-way linear movement
in an information space.
10.3.3 Hierarchical Navigation
Hierarchical navigation is based on a hierarchical classification of an information space
(e.g., of the pages within a web site). It is often used for global navigation around large
web sites with a predefined structure, where it enables users to search on the site by selecting
items from the classification. The main menus (i.e., the navigation bar) of web sites
often correspond to the hierarchical structure of the sites and thus the hierarchical classification
of information provided.
From the graph perspective, hierarchical navigation somewhat corresponds to navigation
in hierarchic clusters – the homepage represents the entire top-level cluster, while
its children and descendants represent the main divisions and subdivisions. Figure 10-5
depicts the classical hierarchical navigation model, which corresponds to a tree. Different
sources also call this model the database or the grid navigation model.
Home Page
Main Divisions
Subdivisions
Figure 10-5. The hierarchical navigation model effectively subdivides the information space
into smaller independent subspaces.
An advantage of hierarchical navigation is that it provides users with information about
the content of other pages and thus enables them to find relevant information quicker. For
example, by following the link “notebooks” in a hierarchical navigation model in an online
shop, one might expect that the following page will contain information about notebooks.
The obvious disadvantage is the necessity of a hierarchical classification scheme and
the fact that navigation paths are predefined by the respective classification. Furthermore,
in the case of large or complex classifications, the understanding of what path to take and