Classification assigns documents or data items to an already known set of classes with already known properties. Document classification or categorization is used when we need to assign documents to one or more categories. This is a frequent use case in information retrieval as well as library science.

The Classification using the naïve Bayes classifier recipe in Chapter 9, Classifications, Recommendations, and Finding Relationships provides a more detailed description about classification use cases, and also gives you an overview of using the Naive Bayes classifier algorithm. This recipe focuses on highlighting the classification support in Apache Mahout for text documents.