As the use of Electronic Medical Records (EMRs) becomes more widespread, so does the need for effective information discovery on them. Recently proposed EMR standards are XML-based, having as a key characteristic the frequent use of ontological references, i.e., ontological concept codes appear as XML elements and are used to associate portions of the EMR document with concepts defined in a domain ontology. In this paper we present the XOntoRank system which tackles the problem of ontology-aware keyword search on XML documents with a particular focus on EMR XML documents. Our running examples and experiments use the Health Level Seven (HL7) Clinical Document Architecture (CDA) Release 2.0 standard of EMR representation and the Systematized Nomenclature of Human and Veterinary Medicine (SNOMED) ontology, although the presented techniques and results are applicable to any EMR hierarchical format and any ontology that defines concepts and relationships. I. OVERVIEW In this paper we presen...