# File lib/rgen/serializer/xmi20_serializer.rb, line 24
        def writeComposites(element)
                eachReferencedElement(element, containmentReferences(element)) do |r,te|
                        attrs = attributeValues(te)
                        attrs << ['xsi:type', "ecore:"+te.class.ecore.name]
                        tag = r.name
                        startTag(tag, attrs)
                        writeComposites(te)
                        endTag(tag)
                end
        end