# Return and register a new empty docunit
	fun new_docunit: DocUnit do
		var mdoc = executor.mdoc
		assert mdoc != null

		var next_number = 1
		var name = executor.xml_name
		if executor.docunits.not_empty and executor.docunits.last.mdoc == mdoc then
			next_number = executor.docunits.last.number + 1
			name += "#" + next_number.to_s
		end

		var res = new DocUnit(mdoc, next_number, "", executor.xml_classname, name)
		executor.docunits.add res
		executor.toolcontext.modelbuilder.unit_entities += 1
		return res
	end