===== Web services =====
  * XML (eXtendible Markup Language) based communication, which combine the advantages of RMI, CORBA, Messaging.
  * Messages and responses are text messages in XML format.
  * Advantage: communication can be followed easily, because data streams are not binary.   
  * Disadvantage: XML processing is more resource intensive than binary data processing.
  * Interface description is in XML format as well. WSDL (Web Service Definition Language), is programming language, platform independent.
  * UDDI (Universal Description, Discovery and Intergration) It is a registry for discovery, describe services.          
  * SOAP (Simple Object Access Protocol) is applied for data transmission.
     * Simpler solution is the XML-RPC. (XML-Remote Process Call)