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278 Selected Studies on Software and Information Systems
what the content of the following pages might be is difficult as is the maintenance of the
classifications themselves.
Some practical applications (e.g., larger web sites) require smoother navigation experience
with both hierarchical and lateral navigation in the information space in order to
make relevant nodes easily accessible from other branches of the tree. Figure 10-6 depicts
the Web navigation model, which combines hierarchical and linear navigation into a complex
interlinked model, which allows easy access from the root (i.e., homepage) to all other
sections and/or databases. Some sources also reference this model as hierarchical navigation
or site-wide navigation.
Figure 10-6. The web navigation model provides quick access by combining hierarchical
and lateral navigation.
10.3.4 Faceted Navigation
The faceted navigation model is based on a faceted classification scheme (The Knowledge
Management Connection, 2006) of an information space. Originating in library sciences,
“a faceted classification differs from a traditional one in that it does not assign fixed slots to subjects
in sequence, but uses clearly defined, mutually exclusive, and collectively exhaustive aspects, properties,
or characteristics of a class or specific subject. Such aspects, properties, or characteristics are
called facets of a class or subject, a term introduced into classification theory and given this new
meaning by the Indian librarian and classificationist S.R. Ranganathan and first used in his Colon
Classification in the early 1930s.” (Wynar & Taylor, 1992, p. 320). For online information
retrieval and navigation however, the library definition of faceted classification can be
somewhat relaxed, e.g. the exhaustiveness is not strictly necessary.
Faceted navigation is widely used by faceted browsers in practical applications (Adkisson,
2005). Example applications include many online shops or information retrieval
systems built around databases, e.g. for job search. As opposed to hierarchical navigation,
faceted navigation is almost exclusively used for dynamic systems, which generate all
views at runtime, due to the exponential number of possible facet and restriction 1 combinations.
1
Each facet consists of a (hierarchical) set of its values – restrictions. For example, New York or
Washington are restrictions in a facet describing location.