Basic Web service platform is
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soap,WSDl,uddi
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XML and HTTP
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SOAP,RPC,XML
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none of the above
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all of the above
Web services fundamentally rely on XML for message formatting and HTTP for transport - these two protocols are the minimum required foundation. SOAP, WSDL, UDDI build upon this base but aren't required for basic XML-over-HTTP web services (often called RESTful or plain XML services).
The foundational, minimal web services platform is built on XML (for structuring/encoding data and messages) plus HTTP (as the transport protocol to send/receive those messages) — this is the classic 'lowest common denominator' description used in early web services literature, since XML+HTTP alone is enough to build a basic web service without requiring the fuller SOAP/WSDL/UDDI stack. SOAP, WSDL, and UDDI are higher-level standards built on top of that XML+HTTP foundation (for messaging format, service description, and discovery respectively), so they represent additional layers, not the basic platform itself.