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1. SOAP--Simple Object Access Protocal

SOAP is a lightweight protocol intented to exchanging structured information in a decentralized, distributed environment.The two major goals for SOAP is simplicity and extensibility.

SOAP is widely used for XML messaging as it :

??? defines thin layer on top of widely understood HTTP?
??? is flexible and extensible?
??? enjoys broad industry and developer community support

Main uses of SOAP are for

??? messaging: sending XML data orders, invoices, forms?
??? RPC: invoking services querying data sources, transacting

2. WSDL--Web Service Definition Language

As?the communication protocols and message formats are standardized?in the web community, it becomes increasingly possible and important to be able to?describe the communication s in some structured way.WSDL addresses this need by defining an XML grammar for describing network services as collections of communication endpoints capable of exchanging messages.

3. ?UDDI--?Universal Description, Discovery, and Integration

UDDI protocol is a central element of the group of related standards that comprise the Web services stack. The specification defines a standard method for publishing and discovering the network-based software components of a service-oriented architecture.

4.? the relationship between SOAP,WSDL and UDDI

web service client 需要定位另一個應用程序或者是網絡上的某一段業務邏輯， client 通過 name 、 catagory 、 identifier 或者 specification 來從 UDDI registry 中查詢服務，定位以后， client 從 UDDI registry 中得到 WSDL 文檔的位置信息。在 WSDL 文檔的 XML schema 中包含了如何訪問 web service 和請求信息的格式， client 按照 xml schema 的格式來創建一個 soap 消息，并向 host 發送請求。