1. Computer-readable storage medium or mediums encoded with instructions that when executed, cause a computer to perform a data structure conversion method, comprising: receiving hierarchically arranged tagged input data in a non-rectangular format; analyzing the hierarchically arranged tagged input data to determine one or more data relationships between one or more parent tags and one or more child tags, wherein each parent tag is associated with two or more child tags; using the determined one or more data relationships to determine rectangularization characteristics for the hierarchically arranged tagged input data; using the rectangularization characteristics to form a mapping specification including one or more data directives, wherein forming the mapping specification includes identifying one or more tables that will be generated from the hierarchically arranged tagged input data, and wherein each association between a parent tag and two or more child tags forms a single corresponding table specific to that association; processing the mapping specification to generate an XPath list, the XPath list specifying data items that are to be extracted from the hierarchically arranged tagged input data; processing the XPath list to gather data from the hierarchically arranged tagged input data; and using the gathered data to generate a map including one or more output observations.