my %book_columns = (
                     'Book_Id' => '@publisherId',
                     'Book_Platform' => '@platform',
                     'Book_Publisher' => '@publisher',
                    );

my %chapter_columns = (
                        'Chapter_Doi' => 'book:meta/@doi',
                        'Chapter_Doi_Prefix' => 'substring-before(book:meta/@doi,"/")',
                        'Chapter_Id' => '@id',
                        'Chapter_Title' => 'book:locator[contains(@xlink:href, "format=epub")]/@xlink:title',                        
                      );