Metadata About What? Distinguishing Between Ontic, Epistemic, and Documental Dimensions in Knowledge Organization

The spread of many new media and formats is changing the scenario faced by knowledge organizers: as printed monographs are not the only standard form of knowledge carrier anymore, the traditional kind of knowledge organization (KO) systems based on academic disciplines is put into question. A sounder foundation can be provided by an analysis of the different dimensions concurring to form the content of any knowledge item-what Brian Vickery described as the steps "from the world to the classifier." The ultimate referents of documents are the phenomena of the real world, that can be ordered by ontology the study of what exists. Phenomena coexist in subjects with the perspectives by which they are considered, pertaining to epistemology, and with the formal features of knowledge carriers, adding a further, pragmatic layer. All these dimensions can be accounted for in metadata, but are often done so in mixed ways, making indexes less rigorous and interoperable. For example, while facet analysis was originally developed for subject indexing, many "faceted" interfaces today mix subject facets with form facets, and schemes presented as "ontologies" for the "semantic Web" also code for non-semantic information. In bibliographic classifications, phenomena are often confused with the disciplines dealing with them, the latter being assumed to be the most useful starting point, for users will have either one or another perspective. A general citation order of dimensions-phenomena, perspective, carrier-is recommended, helping to concentrate most relevant information at the beginning of headings.