Purpose: The principal purpose of the present article is to analyze the technical mechanisms and the categorization procedure of thesaurus, ontology, and their types in storage and retrieval of digital and non-digital content. The types of knowledge organization systems (KOSs) which are addressed in this article are Roget’s thesaurus, thesauri, Micro, Macro and Meta thesaurus, ontologies, and lower, middle, or upper-level ontologies. The study attempts to demonstrate categorization the procedure through determining the position of KOSs in the context of data, information, and knowledge (DIK) by explaining their engineering mechanisms such as data, information, and knowledge engineering in content storage and retrieval, especially digital content. Method: The research method relies on documented and historical methodology. Findings: As ontologies have taken the highest position amidst KOSs in making digital resources available in a web based environment, it is suggested that Iran and other developing countries use the capacities and capabilities of ontologies, especially in the development of national ontologies, in order to construct their knowledge-based infrastructure and system to achieve high performance in digital content engineering and management.
