The research addressed in this thesis, "Modelling authorized metadata in the Resource Description Framework," investigated the most suitable options, using the Resource Description Framework (RDF) data model, for representing authorized bibliographic metadata stored in UNIMARC/A format as semantically related and machine understandable data. The outcome of the research is a concrete product, Ontologija autoriziranih podataka (the Authority Data Ontology or OAP). OAP is based on the abstract syntax of the SKOSXL/RDF data model, and semantics that were modeled according to UNIMARC/A format-specific logical data elements describing bibliographic entities. The OAP element set consists of one hundred and two (102) classes and one hundred and forty seven (147) properties that are modularly extended by applying the Ontologija administrativnih podataka (Ontology of administrative data or ADM). The ADM element set consists of one (1) class and sixteen (16) properties that are modeled according to the UNIMARC/A format-specific logical data elements describing UNIMARC/A record. The OAP + ADM ontological vocabulary, which is abbreviated simply as OAP, achieves the same granularity of authorized metadata as well as a significantly higher number of UNIMARC/A content designators (a combination of field+indicators+subfield). Since the OAP vocabulary is a simpler tool than the UNIMARC/A format but transmits the same information it can be said that this approach achieves a kind of optimization. In terms of methodology, the OAP ontology combines both bottom-up and top-down approaches in trying to strike a balance between: a) clarity and consistency in defining bibliographic entities as OAP classes and their semantic relations as OAP properties, and b) the accuracy and amount of information that describes these entities in the authorized data set. In addition to its theoretical component, the thesis contains the full specification of the OAP ontology in human and machine-readable form in OWL/XML notation and thus meets the theoretical and technical conditions for its implementation.