2. Components of Web Services?

The basic Web services platform is XML + HTTP. All the standard Web Services works using following components

·         SOAP (Simple Object Access Protocol)

·         UDDI (Universal Description, Discovery and Integration)

·         WSDL (Web Services Description Language)

All these components have been discussed in Web Services Architecture section.

How Does it Work?

You can build a Java-based Web Service on Solaris that is accessible from your Visual Basic program that runs on Windows. You can also use C# to build new Web Services on Windows that can be invoked from your Web application that is based on JavaServer Pages (JSP) and runs on Linux.

An Example

Consider a simple account-management and order -processing system. The accounting personnel use a client application built with Visual Basic or JSP to create new accounts and enter new customer orders.

The processing logic for this system is written in Java and resides on a Solaris machine, which also interacts with a database to store the information.

The steps illustrated above are as follows:

1.    The client program bundles the account registration information into a SOAP message.

2.    This SOAP message is sent to the Web Service as the body of an HTTP POST request.

3.    The Web Service unpacks the SOAP request and converts it into a command that the application can understand. The application processes the information as required and responds with a new unique account number for that customer.

4.    Next, the Web Service packages up the response into another SOAP message, which it sends back to the client program in response to its HTTP request.

5.    The client program unpacks the SOAP message to obtain the results of the account registration process. For further details regarding the implementation of Web Services technology, read about the Cape Clear product set and review the product components.

- XML-RPC

This is the simplest XML based protocol for exchanging information between computers.

• XML-RPC is a simple protocol that uses XML messages to perform RPCs.
• Requests are encoded in XML and sent via HTTP POST.
• XML responses are embedded in the body of the HTTP response.
• XML-RPC is platform-independent.
• XML-RPC allows diverse applications to communicate.
• A Java client can speak XML-RPC to a Perl server.
• XML-RPC is the easiest way to get started with web services.

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- SOAP

SOAP is an XML-based protocol for exchanging information between computers.

• SOAP is a communication protocol
• SOAP is for communication between applications
• SOAP is a format for sending messages
• SOAP is designed to communicate via Internet
• SOAP is platform independent
• SOAP is language independent
• SOAP is simple and extensible
• SOAP allows you to get around firewalls
• SOAP will be developed as a W3C standard

To learn more about SOAP visit SOAP Tutorial

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- WSDL

WSDL is an XML-based language for describing Web services and how to access them.

• WSDL stands for Web Services Description Language
• WSDL is an XML based protocol for information exchange in decentralized and distributed environments.
• WSDL is the standard format for describing a web service.
• WSDL definition describes how to access a web service and what operations it will perform.
• WSDL is a language for describing how to interface with XML-based services.
• WSDL is an integral part of UDDI, an XML-based worldwide business registry.
• WSDL is the language that UDDI uses.
• WSDL was developed jointly by Microsoft and IBM.
• WSDL is pronounced as 'wiz-dull' and spelled out as 'W-S-D-L'

To learn more about WSDL visit WSDL Tutorial

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- UDDI

UDDI is an XML-based standard for describing, publishing, and finding Web services.

• UDDI stands for Universal Description, Discovery and Integration.
• UDDI is a specification for a distributed registry of Web services.
• UDDI is platform independent, open framework.
• UDDI can communicate via SOAP, CORBA, Java RMI Protocol.
• UDDI uses WSDL to describe interfaces to web services.
• UDDI is seen with SOAP and WSDL as one of the three foundation standards of web services.
• UDDI is an open industry initiative enabling businesses to discover each other and define how they interact over the Internet.