SOAP

SOAP, Simple Object Access Protocol, and lately also stood for Service Oriented Architecture Protocol, is a XML based protocol that allows a client application exchange information with a application within a remote server over HTTP protocol. SOAP was orignially designed in 1998, with backing from MS, as an object-access protocol. SOAP is currently maintained by the XML Protocol Working Group of the World Wide Web Consortium.

SOAP (Simple Object Access Protocol) is a way for a program running in one kind of operating system (such as Windows 2000) to communicate with a progam in the same or another kind of an operating system (such as Linux) by using the World Wide Web's Hypertext Transfer Protocol (HTTP)and its Extensible Markup Language (XML) as the mechanisms for information exchange. Since Web protocols are installed and available for use by all major operating system platforms, HTTP and XML provide an already at-hand solution to the problem of how programs running under different operating systems in a network can communicate with each other. SOAP specifies exactly how to encode an HTTP header and an XML file so that a program in one computer can call a program in another computer and pass it information. It also specifies how the called program can return a response.
SOAP was developed by Microsoft, DevelopMentor, and Userland Software and has been proposed as a standard interface to the Internet Engineering Task Force (IETF). It is somewhat similar to the Internet Inter-ORB Protocol (IIOP), a protocol that is part of the Common Object Request Broker Architecture (CORBA). Sun Microsystems' Remote Method Invocation (RMI) is a similar client/server interprogram protocol between programs written in Java.
An advantage of SOAP is that program calls are much more likely to get through firewall servers that screen out requests other than those for known applications (through the designated port mechanism). Since HTTP requests are usually allowed through firewalls, programs using SOAP to communicate can be sure that they can communicate with programs anywhere.


SOAP provides a way that allows communications between different programs located remotely running on different operating systems, with different technologies and programming languages.
SOAP makes use of HTTP, allowing more easier commnication behind proxy and firewall than pervious remote execution technology.

WSDL(Web Services Description Language) is an XML-based language for describing web services and how to access them. WSDL is a document written in XML. The document describes a web service. It specifies the location of the service and the operations (or methods) the service exposes.