Web service implementations are now rapidly growing. Web services are easily achieved by XML messaging for most programming languages. Applications usually utilize web services through APIs tied to a specific implementation of SOAP. nML is a dialect of SML and OCaml made in ROPAS. The soaptype type in nML is defined for the value of SOAP encoding. SOAP encoding specification defines rules for serialization of a graph of typed objects using XML Schema. XML Schema validates XML SOAP value. The soaptype type is encoded to XML and decoded from XML. It is necessary to guarantee safe encoding and decoding. So, the definitions for element and type definition in XML Schema are specified by element type and typeinfo type, which include the part of the definitions of XML Schema specification