The data-information-knowledge-wisdom (DIKW) hierarchy or pyramid is a model or construct that has been used widely within information science and knowledge management. The nature of the pyramid is explained, and its historical origin is described. The conceptual components of the pyramid-i.e. data, information, knowledge, and wisdom-are given brief explication. Some modern developments, criticisms, and rebuttals of the DIKW Pyramid are described. Nowadays, the DIKW Pyramid would generally be considered to be unsatisfactory. The arguments and reasoning behind this conclusion are sketched. It is claimed that two more concepts, document and sign, are necessary to provide a fruitful theoretical frame for knowledge organization.