22. A system comprising: a memory and a processor; a search index construction unit stored in the memory and executable by the processor, for receiving, via a network, data relating to at least one input document associated with a new item available for purchase, and for generating search index information for the at least one input document, the data received including a threshold parameter indicating a predetermined threshold similarity of subject matter, wherein a structure of the at least one input document includes at least two fields, the at least two fields each containing content, and the predetermined threshold similarity of subject matter exists at least when a percentage of fields in the structure of the at least one input document correspond to fields in a structure of at least one existing document; and a synonym recognition unit stored in the memory and executable by the processor, in communication with the search index construction unit for: receiving the data relating to the at least one input document, comparing a subject matter of the data relating to the at least one input document to a subject matter of at least further data received from the at least one existing document that relates to an item available for purchase, determining, based at least on the comparison, that the at least one input document and the at least one existing document meet the predetermined threshold similarity of subject matter; responsive to determining that the at least one input document and the at least one existing document meet the predetermined threshold similarity of subject matter, comparing words in the at least one input document to words in the at least one existing document; and designating any dissimilar words or phrases between the at least one input document and the at least one existing document as candidate synonyms; and the search index construction unit being further configured to: merge the candidate synonyms into a search index file, wherein the merging associates the dissimilar words or phrases as synonyms in the search index file, and index the at least one input document into the search index file.
22. A system comprising: a memory and a processor; a search index construction unit stored in the memory and executable by the processor, for receiving, via a network, data relating to at least one input document associated with a new item available for purchase, and for generating search index information for the at least one input document, the data received including a threshold parameter indicating a predetermined threshold similarity of subject matter, wherein a structure of the at least one input document includes at least two fields, the at least two fields each containing content, and the predetermined threshold similarity of subject matter exists at least when a percentage of fields in the structure of the at least one input document correspond to fields in a structure of at least one existing document; and a synonym recognition unit stored in the memory and executable by the processor, in communication with the search index construction unit for: receiving the data relating to the at least one input document, comparing a subject matter of the data relating to the at least one input document to a subject matter of at least further data received from the at least one existing document that relates to an item available for purchase, determining, based at least on the comparison, that the at least one input document and the at least one existing document meet the predetermined threshold similarity of subject matter; responsive to determining that the at least one input document and the at least one existing document meet the predetermined threshold similarity of subject matter, comparing words in the at least one input document to words in the at least one existing document; and designating any dissimilar words or phrases between the at least one input document and the at least one existing document as candidate synonyms; and the search index construction unit being further configured to: merge the candidate synonyms into a search index file, wherein the merging associates the dissimilar words or phrases as synonyms in the search index file, and index the at least one input document into the search index file. 24. The system of claim 22 , wherein the search index construction unit is for receiving data relating to an input document that is accessible through a network resource.