Header section

**Table 29-2: Items permitted in the Header section of an XML document**
Item	Details
XML declaration	This must be the first item in the tree view if it exists. See “XML declaration”.
Document type declaration	If there is an XML declaration, the document type declaration must appear after the XML declaration and any optional processing instructions and comments, and before the root element. Otherwise, this must be the first item in the tree view. See “Document type declaration”.
Comments	See “Comments”.
Processing instructions	See “Processing instructions”.
Root element (start tag)	See “Root element”.
Group header elements	See “Generating group headers”.
Child elements	Child elements in the Header section cannot be iterative except in the case of group DataWindows.