16. A memory data structure comprising: an element table wherein said element table is configured to store a plurality of element records corresponding to a plurality of elements of a markup document so that a relational database includes a plurality of element records, and further wherein each element record includes an assigned element ID field and an element data set field; and an attribute table wherein said attribute table is configured to store a plurality of attribute records corresponding to a plurality of attributes of said markup document so that said relational database includes a plurality of attribute records, and further wherein each attribute data record includes an element ID field and an attribute data set wherein said element table and said attribute table include content of said markup document and further wherein a new markup document having a same content as said markup document can be constructed by retrieving said element data set in each of said plurality of element records stored in said element table of said relational database and by retrieving said attribute data set in each of said plurality of attribute records stored in said attribute table of said relational database.
19. The data structure of claims 16 wherein the element data set includes an element number field.