Simple Object Access Protocol is a protocol for interchange of data in deconcentrated and distributed environs. This is a protocol which has three parts: the first part consists of the framework which describes the information in a message and the method to process it. The next part is a set of rules to govern encoding of instances of application defined data types. The last part being a conventional process which represents remote procedure calls and responses. Simple Object Access Protocol can be used in combination with other variety of protocols.

What is Simple Object Access Protocol?
SOAP stands for a communication protocol. It is used for communicating between applications. It is a format for sending messages via the internet. Based on XML SOAP is platform independent and language independent. It is simple and extensible and allows getting around firewalls.

The Simple Object Access Protocol is a method by which a program running in one kind of operating system to communicate with a program in another same kind or different kind of operating system. SOAP assigns the method of exactly hot to encode an HTTP header file and an XML file so that information can be passed from the calling computer to the called computer or vice versa. It also shows how the called program responds.

SOAP is a high level way for one system to tell the other to do things over the internet. Interoperability is increased as scripted web applications can cross the operating system boundary. Example is the desktop tools being connected to systems running on servers.

Advantages:
o When SOAP is used over HTTP it allows easier communication behind proxies and firewalls.
o It is versatile and allows use of different transport protocols.

Disadvantages:
o SOAP when compared to other middleware technology is slow.
o When SOAP is used with HTTP as a transport protocol then only one party can use the services of the other. Developers cannot use and if they require it then they have to use the polling method.
o SOAP limits the amount of data that can be sent.
o Good analysis of the operation at the application protocol level is problematic.

Why should SOAP be used?

SOAP is used because it has no security problem, no firewalls, and no proxy problem. It has no interoperability problem and can communicate between applications on different operating systems and with applications developed using different programming languages.

Conclusion:

SOAP is considered to be a moderate success. The ideas of this protocol have been used by many. In the beginning SOAP was used mainly for defining a type system because then XML had no schema language. SOAP is a call response mechanism. It operates in a client server prototype. The server is called by the client by passing parameters. To this the server provides a response. Both the call and the response are transported in the form of XML documents. Thus to make SOAP work properly a client and a server is needed.