1. A system for identifying relevant search results via an index, comprising: a query module to receive a search query and to generate a semantic representation for the query comprising a plurality of substructures as a semantic analysis of the search query and a list of key terms, wherein the key terms each comprise a term in the search query or a term related to one of the terms in the search query; an inverted index comprising a set of key terms each associated with a semantic representation and a link to a source reference; a candidate module to identify retrieval candidates for comparing the associated semantic representations with the semantic representation of the search query, comprising: a term selection module to select a subset of the key terms from the search query and to query the inverted index with the key terms in the subset; a result module to identify within the inverted index a result set for each of the key terms in the subset; and a scoring module to score each of the results in the set and to identify a subset of the result sets as the retrieval candidates based on the scoring; and a candidate selection module to select one or more of the retrieval candidates based on a comparison of the semantic representation of the search query with the semantic representations for each of the retrieval candidates.