The web services consist of four layers, as mentioned below:
Service transport:
This layer is the first layer in the web services protocol stack used in transporting XML files between various clients applications. Protocols used in the layer is as follows:
HTTP (Hypertext transfer protocol)
SMTP (Simple Mail Transfer Protocol)
FTP (File Transfer Protocol)
BEEP (Block Extensible Exchange Protocol)
XML Messaging:
This layer is the second layer in the web services protocol stack based on XML model where messages are encoded in common XML format which can be understandable to other client applications. This layer includes the following protocols:
XML - RPC
SOAP (Simple Object Access Protocol)
Service Description:
This layer provides the service description to the public interface like the location of web service, Available functions, And the data types for XML messaging. This layer only includes one language:
WSDL: WSDL stands for Web Service Description Language.
Service Discovery:
This layer in the Web Services protocol stack is used to publish or finding web services over the web. This layer includes:
UDDI (Universal Description, Discovery, and integration).
