1. A structured-text cataloging/searching method for a text searching system, in which a set of texts is searched for specific text contents, comprising the following steps: an already-analyzed-text data generating/cataloging step of cataloging, in a text database, already-analyzed-text data obtained from an analysis of a logical structure of a text to be cataloged, said already-analyzed-text data generating/cataloging step being performed for a plurality of texts to be cataloged; a structure-index creating step of creating a structure index, by sequentially superposing logical structures of said plurality of texts cataloged in said already-analyzed-text data generating/cataloging step; wherein said structure index has a tree-like structure composed of a plurality of metanodes; wherein a context identifier that uniquely identifies one of said metanodes is assigned to each metanode of said structure index; and wherein a group of structure elements having the same position of appearance and the same element type for a plurality of texts are represented by a single metanode; a character-string-index updating step comprising the sub-steps of: extracting partial character strings each having a predetermined character count from each of a plurality of texts to be cataloged; and updating a character string index by cataloging an associative relation between each of said partial character strings and structured character position information of that partial character string in said character string index; a structure-condition judging step of searching the structure index for a set of context identifiers satisfying a specific structure condition; a structured-character-position-information extracting step of extracting partial character strings from a search term, each extracted partial character string having a predetermined character count, and searching the character string index for a set of pieces of structured-character-position information matching said extracted partial character strings; and an index searching step of searching said set of pieces of structured-character-position information for specific pieces of structured-character-position information that have context identifiers found at said structure-condition judging step, and that have a positional relation among said specific pieces of structured-character-position information matching an order of arrangements of said partial character strings in said search term.
1. A structured-text cataloging/searching method for a text searching system, in which a set of texts is searched for specific text contents, comprising the following steps: an already-analyzed-text data generating/cataloging step of cataloging, in a text database, already-analyzed-text data obtained from an analysis of a logical structure of a text to be cataloged, said already-analyzed-text data generating/cataloging step being performed for a plurality of texts to be cataloged; a structure-index creating step of creating a structure index, by sequentially superposing logical structures of said plurality of texts cataloged in said already-analyzed-text data generating/cataloging step; wherein said structure index has a tree-like structure composed of a plurality of metanodes; wherein a context identifier that uniquely identifies one of said metanodes is assigned to each metanode of said structure index; and wherein a group of structure elements having the same position of appearance and the same element type for a plurality of texts are represented by a single metanode; a character-string-index updating step comprising the sub-steps of: extracting partial character strings each having a predetermined character count from each of a plurality of texts to be cataloged; and updating a character string index by cataloging an associative relation between each of said partial character strings and structured character position information of that partial character string in said character string index; a structure-condition judging step of searching the structure index for a set of context identifiers satisfying a specific structure condition; a structured-character-position-information extracting step of extracting partial character strings from a search term, each extracted partial character string having a predetermined character count, and searching the character string index for a set of pieces of structured-character-position information matching said extracted partial character strings; and an index searching step of searching said set of pieces of structured-character-position information for specific pieces of structured-character-position information that have context identifiers found at said structure-condition judging step, and that have a positional relation among said specific pieces of structured-character-position information matching an order of arrangements of said partial character strings in said search term. 3. A structured-text cataloging/searching method according to claim 1, in which said structure-index creating step creates a structure index by sequentially superposing logical structures of a plurality of texts to be cataloged; wherein the tree-like structures of two of said texts to be cataloged are superposed on each other in said structure index by: comparing nodes of one of said tree-like structures of said two texts with nodes of the other of said tree-like structures of said two texts; regarding a root node in said one of said tree-like structures as a counterpart that mutually corresponds to a root node in said other of said tree-like structures; regarding a non-root node in said one of said tree-like structures of said two texts as a counterpart that mutually corresponds to a non-root node in said other of said tree-like structures if the non-root node in said one of said tree-like structures has a directly superordinate node mutually corresponding to a directly superordinate node of the non-root node in said other of said tree-like structures, if the non-root node in said one of said tree-like structures is the same type of node as the non-root node in said other of said tree-like structures, and if the non-root node in said one of said tree-like structures has the same appearance order number as the non-root node in said other of said tree-like structures, wherein the appearance order number indicates a position in a normal order of an array of brother nodes of the same type of node found by counting said brother nodes, starting from the head of said array; and representing two mutually corresponding nodes by a single metanode in said structure index.