1. A computer implemented method for indexing and retrieving documents stored in a database, comprising the steps of: extracting a document feature vector from each of a plurality of documents; indexing each of the plurality of documents according the associated document feature vector; converting, using a processor, a spoken query to an intermediate representation representing possible sequential combinations of terms in the spoken query, the intermediate representation is selected from a group consisting of a lattice of terms, an n-best list, or combination thereof; generating a query certainty vector from the intermediate representation; and comparing the query certainty vector to each of the document feature vectors to retrieve a ranked result set of documents.