In this paper, the functional and relational characteristics and requirements for various types of semantic interoperability in a comprehensive international knowledge organisation system are being discussed with regard to an analysis of the underlying retrieval paradigms. Furthermore, this paper analyses the potential benefits and perspectives of the selective transfer of modelling strategies from the field of semantic technologies for the refinement of relational structures of inter-system and inter-concept relations as a requirement for expressive and functional indexing languages supporting advanced types of semantic interoperability.