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 for each of a plurality of passages comprising a plurality of substructures and further associated with a link to a reference document for the passage; a candidate module to identify one or more of the passages as retrieval candidates by comparing the semantic representations associated with the passages 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 based on a distance of relationships of the substructures in the semantic representation of the search query and the semantic representation of the passages 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, wherein the modules are executed via a computer processor.