How to avoid hard coding second XML document

[wxdqz]

The concept is:I am producing a second XML from sub parts of a first XML. I want to graball of the data and sub-tags from <author>, both data and tagging, from thefirst XML to be placed in the second XML without hard-coding all of the child-elements.How can I do this given the following example?First XML ( Original info )<doc><author><firstname>Joe<\firstname><lastname>Smith<\lastname><\author><publisher>blah blah blah<\publisher><\doc>Second XML ( Desired Result )<author_list><author><firstname>Joe<\firstname><lastname>Smith<\lastname><\author><\authors_list>