# File nqxml/document.rb, line 44
 def setRootNode(node)
	    if node.nil?
		raise ArgumentError, 'root node may not be nil', caller
	    end

	    # Although this check is performed by the tree parser, we check
	    # again here. The document's creation may be in the hands of
	    # someone (or something) else.
	    raise ParserError.new("root node already defined") if @rootNode

	    @rootNode = node
	end