1. A non-NLP (natural language processing) computer-implemented method of performing purely an ontology-based search of an electronic document by selecting keywords representative of the document from an ontology, said computer-implemented method comprising: computing, for each term in said ontology, a value representative of a frequency of occurrence of said term in said document; selecting a subset of terms of said ontology as keywords representative of said document based on said value; and presenting said keywords as an output of a purely ontology-based search of said document, wherein said purely ontology-based search of said document consists of a non-concept-based search of said document.