Many competing definitions for the terms data, information, metadata, and knowledge can be traced in the library and information science literature. The lack of a clear consensus in the way reference is made to the corresponding fundamental concepts is intensified if one considers additional disciplinary perspectives, e.g. database technology, data mining, etc. In the present paper, we use a common sense approach borrowed from the data mining community, which has successfully solved many data processing problems, to selectively survey the literature, and define these terms in a way that can advance the interdisciplinary development of information systems.