These three elements are:

1. White pages: It include basic information which is related to the company and its business and allowed others to discover your web service in unique identifier.

2. Yellow pages: It include more details about the company for example  the kind of electronic capabilities the company on this basis company offer to anyone to do business with it.

3. Green pages: It include the technical information about a web service that make helps someone to allowed bind customer to the Web service when he has been found.

RPC is a older technology  stands for Remote Procedure Call. RPC is a mechanism to call  function or procedure that are  available on a remote computer. XML-RPC provide facility to computer to call procedure from other remote computer and make function across network. XML-RPC uses the HTTP protocol to transfer information between a client computer and a server computer. It uses XML vocabulary to describe nature of request and response. XML-RPC client specified only a procedure name and parameters  and the server returns fault or response to the client but both are in XML format, with XML-RPC and web services, however, the Web becomes a collection of procedural connections where computers exchange information along tightly bound paths.

1. Component-based programming has become more popular 

For example end-to-end e-commerce solution residing on a Web farm needs to submit orders to a back-end Enterprise Resource Planning (ERP) application that resides on different hardware and might run on a different operating system. The Microsoft Distributed Component Object Model (DCOM), a distributed object infrastructure that allows an application to invoke Component Object Model (COM) components installed on another server, has been ported to a number of non-Windows platforms. But DCOM has never gained wide acceptance on these platforms, so it is rarely used to facilitate communication between Windows and non-Windows computers. ERP software vendors often create components for the Windows platform that communicate with the back-end system via a proprietary protocol.

2. Some services related to application 

For example, if the e-commerce application accepts credit card payment for goods purchased by the customer, it must elicit the services of the merchant bank to process the customer\'s credit card information. But for all practical purposes, DCOM and related technologies such as CORBA and Java RMI are limited to applications and components installed within the corporate datacenter. Two primary reasons for this are that by default these technologies leverage proprietary protocols and these protocols are inherently connection oriented.

3. Interoperability, The remote service must be able to be consumed by clients on other platforms.

4. Internet friendliness, The solution should work well for supporting clients that access the remote service from the Internet.

5. Strongly typed interfaces, There should be no ambiguity about the type of data sent to and received from a remote service.

1. Interoperability: Most important benefit  of Web services, its  work outside of private networks and  offering developers to find their solutions in appropriate way. Its provide Interoperability between many software\'s running ion different platform. Web Services are virtually platform-independent

2. Reusability: Web services use open standards and protocols. Deployment of services possible easily because  they are not a component-based model of application for development. This makes it easy to reuse Web Service components as appropriate in other services.

3. Deploy ability: Web services deploy over the Web and any user use this without any independent and mapping problems.

4. Usability: Web services allow the reuse of services and components within an infrastructure. Web Services allow the business logic of  different platform and exposed it over the Internet. This thigh provide the facility to use web services any where for different platform.

1. Web services suffered poor performance in comparison other distributed application  RMI, CORBA, or DCOM.

2. XML explicitly does not count among its design goals either conciseness of encoding or efficiency of parsing.

3. Transaction in Web Services is not infancy like other distributed standards like CORBA. The web service transaction is nonexistent.

4. When client make a request to the server. When  the server  response at that time if power gone and client end crash, in this condition server never known that client not activated.

1. XML-based: XML based is totally platform independent and run on any operating system and also language independent

2. Loosely Coupled: Loosely coupled means consumer of a web service does not tied web services directly.  A tightly coupled system implies that the client and server logic are closely tied to one another.

3. Coarse-grained: Its provide Coarse-grained facility for JAVA programs and methods.

4. Ability to be synchronous or asynchronous: Synchronized provide the facility  to binding the client when client want to execute the Web Services. Means client synchronously used the services.  Asynchronous operations allowed  the client  a client to invoke the web service when client want to execute other functions.

5. Supports to Remote Procedure Calls (RPCs): Web services support the remote procedure calls when transaction occur during exchange of documents.

6. Supports document exchange: Web services support the transfer the  exchange of documents to utilize business transaction. Exchange of document totally XML based.

7. Interoperability provide system to system work without any external effort.

1. Service provider: The service provider provide the service and  implements the service. It make the service available on the internet

2. Service requestor: This is any consumer of the web service. The requestor utilizes an existing web service by opening a network connection and sending an XML request.

3. Service registry: Centralized directory of services. It is logically  registry provides a central place. At that place developers published  new services  and find existing services.

4. Service transport: Service transport is responsible for transporting messages between applications. Its includes hypertext transfer protocol (HTTP), Simple Mail Transfer Protocol (SMTP), file transfer protocol (FTP). Its include something newer protocol  named Blocks Extensible Exchange Protocol (BEEP).

5. XML messaging: Responsible for encoding messages in a common XML format because that messages must be understandable at the  second  end. Currently, this layer includes XML-RPC and SOAP.

6. Service description: Responsible for describing the public interface to a specific web service. Currently, service description is handled via the Web Service Description Language (WSDL).

7. Service discovery: Responsible for centralizing services into a common registry. Its provide easy publish and find  functionality for the developer. Currently, service discovery is handled via Universal Description, Discovery, and Integration (UDDI).