19. A logical structure model creation assistance method for assisting in the creation of a logical structure model, which stores, from an image in which character strings associated respectively with a plurality of logical elements constituting a logical structure are described, the logical elements, character strings associated with the logical elements, and the logical structure, the method comprising: firstly extracting a character string in an input image and the logical structure among the character strings in the input image based on a result of recognition of the input image; selecting one among the plurality of logical elements according to the degrees of similarity between the extracted character strings in the input image and the character strings associated respectively with the plurality of logical elements stored in the logical structure model; secondly extracting a character string associated with the selected logical element and a character string in the input image associated with the logical element based on the logical structure among the extracted character strings in the input image; and displaying the extracted character string as a candidate update target for the character string associated with the selected logical element.
19. A logical structure model creation assistance method for assisting in the creation of a logical structure model, which stores, from an image in which character strings associated respectively with a plurality of logical elements constituting a logical structure are described, the logical elements, character strings associated with the logical elements, and the logical structure, the method comprising: firstly extracting a character string in an input image and the logical structure among the character strings in the input image based on a result of recognition of the input image; selecting one among the plurality of logical elements according to the degrees of similarity between the extracted character strings in the input image and the character strings associated respectively with the plurality of logical elements stored in the logical structure model; secondly extracting a character string associated with the selected logical element and a character string in the input image associated with the logical element based on the logical structure among the extracted character strings in the input image; and displaying the extracted character string as a candidate update target for the character string associated with the selected logical element. 20. The logical structure model creation assistance method according to claim 19 , wherein, the logical structure stored in the logical structure model has a hierarchical structure, the selecting assigns the order of priority and selects several logical elements among the plurality of logical elements, according to the degrees of similarity between the extracted character strings in the input image and the character strings associated respectively with the plurality of logical elements stored in the logical structure model, and lets the logical element with the highest priority to be a reference logical element, and further comprising, determining for the several selected logical elements according to the priority, the degrees of similarity between the character strings associated respectively with a logical element at an upper level, a logical element at a lower level or a logical element at the same level in the hierarchical structure of the reference logical element and the character strings associated respectively with the plurality of extracted logical elements, and estimating, based on the result of the determination, the degree of similarity between the logical structure stored in the logical structure model, and the logical structure among the extracted character strings in the input image.