PurposeThe purpose of this paper is to address a library service based on semantic web technologies capable of exposing knowledge that is otherwise hidden in a library's subject headings repository.Design/methodology/approachThe proposed service implements a web‐based information seeking process that combines browsing and searching of information assets within a library, based on their corresponding subject headings. The underlying subject headings hierarchy is the Greek translation of a subset of the official Library of Congress subject headings. The information seeking process exposes the expressiveness of an underlying ontology capable of modeling subject headings together with their relations.FindingsIn order to assess the effectiveness of the proposed approach in a real‐world scenario, the library service is integrated into a working OPAC located at the Ionian University in Greece. Thus, the library service contributes to the fast retrieval of information. Moreover, during the information seeking process, users underpin their cognitive learning.Originality/valueThe paper introduces a novel service for the library domain capable of being integrated in many library portals. Serving as a semantic web application, the proposed work promotes interactive navigation in ontology structures that could be potentially exploited by ontologies developed in other domains.