Document classification

Document classification/categorization is a problem in information science. The task is to assign an electronic document to one or more categories, based on its contents. Document classification tasks can be divided into two sorts: supervised document classification where some external mechanism (such as human feedback) provides information on the correct classification for documents, and unsupervised document classification, where the classification must be done entirely without reference to external information.

Techniques
Document classification techniques include: and approaches based on natural language processing.
 * naive Bayes classifier
 * tf-idf
 * latent semantic indexing
 * support vector machines
 * artificial neural network
 * kNN
 * decision trees, such as ID3
 * Concept Mining

Applications
A recent notable use of document classification techniques has been spam filtering which tries to discern E-mail spam messages from legitimate emails.