Document theory examines the concept of a document and how it can serve with other concepts to understand communication, documentation, information, and knowledge. Knowledge organization itself is in practice based on die arrangement of documents representing concepts and knowledge. The word "document" commonly refers to a text or graphic record, but, in a semiotic perspective, non-graphic objects can also be regarded as signifying and, therefore, as documents. The steady increase in the variety and number of documents since prehistoric times enables the development of communities, the division of labor, and reduction of the constraints of space and time. Documents arc related to data, facts, texts, works, information, knowledge, signs, and other documents. Documents have physical (material), cognitive, and social aspects. © 2018 International Society for Knowledge Organization. All Rights Reserved.