The Data Model Resource Book, Volume 3: Universal Patterns for Data Modeling

Silverston c05.tex V2 - 11/21/2008 3:04am Page 189

What Are Types, Categorizations, and Taxonomies? 189

The relevance of each pattern

Insights into each pattern

When to use and not to use different patterns

A synopsis of each of the patterns, pros, and cons

What Are Types, Categorizations, and Taxonomies?

Types, categories, and taxonomies are closely related concepts, but each has a

slightly different meaning. Each of the patterns described in this chapter may

support a type, category, and/or a taxonomy.

Types may be defined as ‘‘a number of things or persons sharing a particular

characteristic, or set of characteristics that cause them to be regarded as a group,

more or less precisely defined or designated.’’

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In our patterns, a type entity

classifies the ‘base’ entity we are trying to classify in a very simple way. For

example, if we are classifying an ORDER, then there may be a related ORDER

TYPE that would contain instances of ‘‘Sales Order’’ or ‘‘Purchase Order’’

which could be considered types of orders.

Categorization can be defined as ‘‘any general or comprehensive division.’’

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The key difference between a categorization and a type is that a categorization

is more comprehensive than a type, and it involves different ways to classify

an entity, that is, a categorization includes many different ’’types of types’’.

For example, a person may be categorized many different ways (e.g., by level

of income, ...