7. A system for creating an index for searching a structured document having a document data-structure comprising: a structured document registration unit for obtaining the structured document and storing the structured document in a storage unit in the system; a document data-structure extraction processor for analyzing the stored structured document and extracting a document data-structure; a logical structure index creation processor for normalizing the extracted document data-structure and creating a logical structure index composed of a plurality of elements having a hierarchical structure; an element appearance control processor for extracting an appearance number of a terminal element positioned at an end in the created logical structure index; an index definition creation processor for, obtaining an element for creating an index for packaging a plurality of the terminal elements which have been counted among the extracted appearance number, having same element names, and are present in different hierarchical positions of the logical structure index, when comparing the extracted appearance number to a first predetermined threshold indicates that the extracted appearance number is larger than the first predetermined threshold; and a value index creation processor for creating a packaged index from a path of the obtained element in the logical structure index.
7. A system for creating an index for searching a structured document having a document data-structure comprising: a structured document registration unit for obtaining the structured document and storing the structured document in a storage unit in the system; a document data-structure extraction processor for analyzing the stored structured document and extracting a document data-structure; a logical structure index creation processor for normalizing the extracted document data-structure and creating a logical structure index composed of a plurality of elements having a hierarchical structure; an element appearance control processor for extracting an appearance number of a terminal element positioned at an end in the created logical structure index; an index definition creation processor for, obtaining an element for creating an index for packaging a plurality of the terminal elements which have been counted among the extracted appearance number, having same element names, and are present in different hierarchical positions of the logical structure index, when comparing the extracted appearance number to a first predetermined threshold indicates that the extracted appearance number is larger than the first predetermined threshold; and a value index creation processor for creating a packaged index from a path of the obtained element in the logical structure index. 8. The system according to claim 7 , wherein the value creation processor comprises means for outputting a display screen including the extracted elements, and creating a path of the extracted elements in the logical structure index as an index, only if information instructing a creation of the index is obtained.