Currently the XML serialisers both output namespaces that are not required:

xmlns:xsd="http://www.w3.org/2001/XMLSchema"; xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";

I'm not sure about the Data Contract serializer, but it is not difficult to supress these...

Just pass into the Serialize method an XmlSerializerNamespaces:

var xmlSerializerNamespaces = new XmlSerializerNamespaces();
xmlSerializerNamespaces.Add(String.Empty, defaultNamespace);

var xmlSerializer = new XmlSerializer(objectType);
xmlSerializer.Serialize(xmlWriter, toBeSerialised, xmlSerializerNamespaces);

Where defaultNamespace could be set on the GlobalConfiguration.Configuration.Formatters.XmlFormatter or it could be read from the XmlRoot attribute (if present) on the object being serialised.