Taxonomies are typically hierarchical (see Figure
4.4). They can define the hypernym-hyponym and meronym-holonym relationships
between words (discussed in the sidebar ???what??™s in a word????). They can also be used
to define broader and narrower concepts, such as philosophy and epistemology.
The most famous taxonomy is probably the dewey decimal classification system.
dewey designed a system with 10 top-level categories, followed by 10 subcategories,
followed by another 10 subcategories.
In dewey??™s classification system, each book is assigned to a single category. In most
libraries you??™ll find Stephen hawking??™s A Brief History of Time at 523.1 in the Astronomy
and Space Sciences category.
parent
child child
Figure 4.4 In a simple taxonomy each
node has only one parent node but can
have zero, one, or more child nodes.
dewey set out to organize all human knowledge into his taxonomy, but most taxonomy
efforts have more modest goals. Many web sites use a taxonomic structure for
their content.
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