Revision with unchanged content. Everyday, we engage in the use of networked information systems and websites to search for information. Whatever information users search for, it is highly possible that it can be found somewhere in the digital world. But, oftentimes, searching for information is neither effective nor efficient. When a user searches for information, a system often returns a large number of irrelevant results. Thus, the critical issue facing the current digital world is not the lack of information, but ill-structured information and inefficient information retrieval.This study concerned the testing of user performance when searching an ontology-driven information retrieval (ONTOIR) system that shows explicit relationships among resources. The goal was to examine whether or not ontology enhances user performance in terms of recall and search time. The experiment was conducted with 40 participants to evaluate and compare the differences in user performance (recall and search time) between an ontology-driven information retrieval system and a traditional, thesaurus-driven information retrieval system. Better recall and shorter search time were found when conducting relationship-based queries in an ontology-driven information retrieval system as compared to a thesaurus-based system. The book is addressed to knowledge managers, information architects, and other information professionals.