Vocabulary control comes in many shapes and sizes. At its most vague, a controlled vocabulary is any defined subset of natural language. At its simplest, a controlled vocabulary is a list of equivalent terms in the form of a synonym ring, or a list of preferred terms in the form of an authority file. Define hierarchical relationships between terms (e.g., broader, narrower) and you’ve got a classification scheme. Model associative relationships between concepts (e.g., see also, see related) and you’re working on a thesaurus. Figure 9-1 illustrates the relationships between different types of controlled vocabularies.
Figure 9-1. Types of controlled vocabularies
Since a full-blown thesaurus integrates all the relationships and capabilities of the simpler forms, let’s explore each of these building blocks before taking a close look at the “Swiss Army Knife” of controlled vocabularies.
A synonym ring (see Figure 9-2) connects a set of words that are defined as equivalent for the purposes of retrieval. In practice, these words are often not true synonyms. For example, imagine you’re redesigning a consumer portal that provides ratings information about household products from several companies.
Figure 9-2. A synonym ring
When you examine the search logs ...