A method of providing semantically relevant, ranked search results is described. An assignment of an occurrence of a term within a document to an ontological node is received based on usage of the occurrence of the term within the document. An accuracy value associated with the assignment is determined by comparing the assignment with a baseline assignment. A consistency value associated with an assignor is determined based on a repeatability of a plurality of assignments by the assignor. An assignor relevance score for the occurrence of the term is determined by statistically combining the accuracy value and the consistency value. An overall semantic relevance value for the occurrence of the term is determined by statistically combining the assignor relevance score determined for a plurality of assignors. The documents are ranked based on the overall semantic relevance value and presented in response to a search request.