Patent ID: 7664773

Claim:
A method for storing structured data items, each including an individual hierarchical structure of a plurality of elements, comprising: (a) preparing a first memory having a plurality of document storage areas each including a plurality of element storage areas to which element IDs are assigned respectively as physical addresses of the element storage areas in each document storage area; (b) storing, in a second memory, a first structure template including a plurality of fixed allocation elements, each fixed allocation element being associated with an element storage area and an element ID of the element storage area, which was previously assigned to each fixed allocation element as a fixed element ID of the fixed allocation element; (c) inputting a structured data item including an individual hierarchical structure; (d) extracting, from the structured data item, the individual hierarchical structure thereof, the individual hierarchical structure extracted including the fixed allocation elements; (e) updating the first structure template by adding an element which is present in the individual hierarchical structure extracted but is not present in the first structure template; (f) storing the structured data item in one of the document storage areas in the first memory, each fixed allocation element of the structured data item being stored in a corresponding element storage area whose element ID is the same as the fixed element ID of the fixed allocation element, each element other than the fixed allocation elements in the structure data item being assigned an element ID which is not among one of the fixed element IDs, and being stored in the corresponding element storage area having the element ID assigned to the element; (g) repeating (c) to (f), to store a given number of structured data items in the first memory; (h) calculating an occurrence frequency of each element of the first structure template, in the structured data items stored in the first memory; and (i) extracting, from the first structure template, a second structure template including the fixed allocation elements and a new fixed allocation element which is an element whose occurrence frequency is more than or equal to a predetermined threshold value, to assign, to the new fixed allocation element, an element storage area and an element ID of the element storage area as a fixed element ID of the new fixed allocation element, wherein the element ID is the physical address of the element storage area.