What example illustrates double indexing?

Double indexing refers to a classification system where a primary category is further divided into more specific subcategories. This helps in better organizing and retrieving information within a database or directory.

In the context provided, the example showcasing double indexing is the one where Multipurpose Centers (TC-5500) are categorized under a general heading, and Youth Centers (TC-5500.9800) represent a specific type of Multipurpose Center. Here, the first code (TC-5500) is the broader classification that includes various kinds of multipurpose facilities, while the second code (TC-5500.9800) refers to a distinct, specialized type that focuses specifically on youth services.

This hierarchical structure allows for more precise search capabilities and ensures that users can find specific services related to youth under the broader category of multipurpose resources. By utilizing such a classification scheme, organizations can streamline their information management and enhance user accessibility to specific types of programs or services.

In contrast, while other options present categorizations, they do not illustrate the concept of double indexing as clearly as the example of Multipurpose Centers and Youth Centers, where one is a subset of the other with a distinct focus.