5. A system comprising: one or more data processing devices; and one or more tangible computer-readable storage media having stored thereon computer executable components comprising: a storage module configured to store an inverted index of documents in the system and forward indices corresponding to each of the documents; an input module configured to receive an inquiry word; and a search module configured to segment the inquiry word into one or more keywords, search the inverted index to determine one or more documents in which one or more of the keywords are matched, search a forward index of a respective document of the determined one or more documents to generate an abstract for the respective document, the search including: determining a length limit of the abstract; identifying a plurality of portions within the respective document, each portion of the plurality of portions including a respective beginning position in the respective document and a respective ending position in the respective document, the identifying including identifying, within the respective document, every portion that is within the length limit by traversing the forward index character-by-character or word-by-word; finding a portion among the plurality of portions, the portion including a highest number of the one or more keywords between a beginning position and an ending position compared with any other portion of the plurality of portions; and selecting the found portion to be the abstract of the respective document.
5. A system comprising: one or more data processing devices; and one or more tangible computer-readable storage media having stored thereon computer executable components comprising: a storage module configured to store an inverted index of documents in the system and forward indices corresponding to each of the documents; an input module configured to receive an inquiry word; and a search module configured to segment the inquiry word into one or more keywords, search the inverted index to determine one or more documents in which one or more of the keywords are matched, search a forward index of a respective document of the determined one or more documents to generate an abstract for the respective document, the search including: determining a length limit of the abstract; identifying a plurality of portions within the respective document, each portion of the plurality of portions including a respective beginning position in the respective document and a respective ending position in the respective document, the identifying including identifying, within the respective document, every portion that is within the length limit by traversing the forward index character-by-character or word-by-word; finding a portion among the plurality of portions, the portion including a highest number of the one or more keywords between a beginning position and an ending position compared with any other portion of the plurality of portions; and selecting the found portion to be the abstract of the respective document. 8. The system of claim 5 , wherein the search module further comprises: a search sub-module configured to segment the inquiry word into the one or more keywords, and determine the one or more documents matching the one or more keywords based on the inverted index; an abstract generation sub-module configured to traverse at least one word in the forward index of the respective documents, record the at least one traversed word and a location of the at least one traversed word in a first data structure by using the location of the traversed word as an index of the first data structure; when the at least one traversed word matches one of the keywords, record the traversed word and the location of the at least one traversed word in a second data structure by using the at least one traversed word as an index of the second data structure; determine the beginning position of the abstract and the ending position of the abstract according to the first data structure, the second data structure, and the length limit, wherein: in response to determining that a total length of traversed words in the first data structure is less than the length limit, set the beginning position to a location of a first traversed word in the first data structure and set the ending position to a location of a last traversed word in the first data structure; or in response to determining that the total length of traversed words in the first data structure is not less than the length limit, utilize the second data structure to determine one or more portions of the respective document that have lengths less than the length limit, to determine the portion of the one or more portions that has the highest number of the one or more keywords, and to set the beginning position and ending position of the portion based on the locations of a first traversed word and a last traversed word, respectively, in the portion; and generate the abstract according to the determined beginning position and the ending position; and a submission sub-module configured to submit to an output module the generated abstracts.