1. A document structure inspection method comprising the step of: applying a document structure alteration rule, which is stored by storage means, to a first document structure definition expressing the structure of a structured document written in a document structure definition language for the purpose of effecting conversion to generate a second document structure definition; wherein said document structure alteration rule includes a replacement rule for setting a document structure definition element name that is to be replaced in accordance with an element name contained in a document structure definition targeted for application and an addition rule for setting a document structure definition element name that is to be added in accordance with the end of an element name contained in a document structure definition targeted for application, wherein said conversion creates said second document structure definition by replacing a specified element with an element set in a document structure definition stored in said storage means when an element name targeted for application, which is set in said replacement rule, appears in said first document structure definition, and by adding a set document structure definition element, which is stored in said storage means, to a location after a specified element when an element name targeted for application, which is set in said addition rule, appears in said first document structure definition; and conducting an inspection on an individual element name basis to determine whether said second document structure definition is consistent with a corresponding document structure definition stored in said storage means.