# Set the Namespace URI of a specific attribute.
	#
	# Parameters:
	#
	# * `index`: index of the attribute (zero-based).
	# * `uri`: attribute's Namespace URI, or the empty string for none.
	fun uri=(index: Int, uri: String) do
		assert index_in_bounds: index >= 0 and index < length
		data[index * 5] = uri
	end