public string Serialize()
{
string xml = "";
if (data != null) xml += "\r\n<data>" + SecurityElement.Escape(data) + "</data>";
if (header != null) xml += "\r\n<header>" + header.Serialize() + "</header>";
if (signature != null) xml += "\r\n<signature>" + SecurityElement.Escape(signature) + "</signature>";
if (version != null) xml += "\r\n<version>" + SecurityElement.Escape(version) + "</version>";
return xml;
}