8. A computing system for information retrieval, the computing system comprising: one or more hardware computer processors programmed, via software instructions, to: access a plurality of documents, each document from the plurality of documents associated with one or more words; identify, from the plurality of documents, a plurality of segments, wherein each segment of the plurality of segments is identified based at least on analyzing one or more features of each document from the plurality of documents, the one or more features comprising at least one of casing, spacing, punctuation, or common words, and wherein each segment of the plurality of segments is at least associated with a portion of a respective document; access a plurality of concepts of interest for identification within the plurality of segments; access a mapping from respective ones of the plurality of concepts to respective keywords from an initial keyword set; determine a first set of segments from the plurality of segments based at least on the initial keyword set, respective ones from the initial keyword set corresponding to respective words from the first set of segments; determine a related keyword set based at least on identifying respective words from the first set of segments that were not present in the initial set of keywords; update the mapping to include associations between respective ones of the plurality of concepts and respective related keywords; determine a second set of segments from the plurality of segments based at least on the related keyword set, respective ones from the related keyword set corresponding to respective words from the second set of segments; index the plurality of concepts, wherein respective ones of the plurality of concepts are associated with at least one segment from the first set of segments or the second set of segments, wherein the association between respective ones of the plurality of concepts and the at least one segment is based at least on the mapping; determine a ranking associated with a first segment from the first set of segments or the second set of segments, and a first concept from the plurality of concepts, wherein the ranking is based on at least one of: a density of first concept keywords in the first segment, wherein the density is based at least on a ratio of a quantity of first concept keywords in the first segment to a quantity of words in the first segment; or a distribution of first concept keywords within the first segment, wherein the distribution is based on at least one of a longest span in the first segment without any mention of first concept keywords or a median gap between consecutive mentions of respective first concept keywords in the first segment; and store the index and the ranking in a non-transitory computer storage.
8. A computing system for information retrieval, the computing system comprising: one or more hardware computer processors programmed, via software instructions, to: access a plurality of documents, each document from the plurality of documents associated with one or more words; identify, from the plurality of documents, a plurality of segments, wherein each segment of the plurality of segments is identified based at least on analyzing one or more features of each document from the plurality of documents, the one or more features comprising at least one of casing, spacing, punctuation, or common words, and wherein each segment of the plurality of segments is at least associated with a portion of a respective document; access a plurality of concepts of interest for identification within the plurality of segments; access a mapping from respective ones of the plurality of concepts to respective keywords from an initial keyword set; determine a first set of segments from the plurality of segments based at least on the initial keyword set, respective ones from the initial keyword set corresponding to respective words from the first set of segments; determine a related keyword set based at least on identifying respective words from the first set of segments that were not present in the initial set of keywords; update the mapping to include associations between respective ones of the plurality of concepts and respective related keywords; determine a second set of segments from the plurality of segments based at least on the related keyword set, respective ones from the related keyword set corresponding to respective words from the second set of segments; index the plurality of concepts, wherein respective ones of the plurality of concepts are associated with at least one segment from the first set of segments or the second set of segments, wherein the association between respective ones of the plurality of concepts and the at least one segment is based at least on the mapping; determine a ranking associated with a first segment from the first set of segments or the second set of segments, and a first concept from the plurality of concepts, wherein the ranking is based on at least one of: a density of first concept keywords in the first segment, wherein the density is based at least on a ratio of a quantity of first concept keywords in the first segment to a quantity of words in the first segment; or a distribution of first concept keywords within the first segment, wherein the distribution is based on at least one of a longest span in the first segment without any mention of first concept keywords or a median gap between consecutive mentions of respective first concept keywords in the first segment; and store the index and the ranking in a non-transitory computer storage. 9. The computing system of claim 8 , wherein the one or more hardware processors are further programmed, via the software instructions, to: receive input comprising at least the first concept; in response to the input, query the non-transitory computer storage to retrieve a result set based on the first concept and the index, the result set comprising at least the first segment and a second segment; and transmit the retrieved result set for presentation in a user interface, wherein the ranking affects the presentation of the first segment and the second segment in the user interface.