Hello
SOAP is an XML-based protocol for exchanging information in a decentralized, distributed environment. It was made for Web, a combination of XML and HTTP opens up new options for distributed data exchange and interaction in a loosely coupled web environment. SOAP is a technology that allows XML to move easily over the Web. SOAP does this trough an XML envelope for delivering XML content and specifying a set of rules for services to follow when they receive a SOAP message.
The fundamental change brought about by SOAP has been the ability to move data anywhere across the Web. Before SOAP there were only two main options for moving data between partners.
One was to build a wide area network spanning a broad geographic region and let the partners plug into it. This was the approach taken by EDI, which defined messages and protocols for data transfer but left the network details up to the partners. The result was a collection of networks that pretty much locked the partners in and made it difficult and expensive to reach out to other EDI networks and costly to bring in new partners.
The second approach for moving data between partners was to build a distributed object infrastructure than ran over the internet. This was the approach taken by Common Object Request Broker (CORBA), Remote Method Invocation (RMI) and Distributed Component Object Model (DCOM). The problem was that each had to decide on a protocol that could sit on top of TCP/IP and handle inter object communication. CORBA Chose Internet Inter-ORB Protocol (IIOP), DCOM chose object Remote Procedure Call (ORPC), and RMI chose Remote Method Protocol (JRMP). While this approach reduced the need to share the same underlying network, the drawback was that CORBA could talk to CORBA, RMI to RMI and DCOM to DCOM, but they neither could talk to each other nor directly to the web except through special sockets that required adding extra layers to an already complex architecture.
SOAP the third option, combines the data capabilities of XML with the transport capabilities of HTTP, there by overcoming drawbacks of both EDI and tightly coupled distributed object system such as CORBA, RMI and DCOM. It does this by breaking dependence between data and transport and in doing so opens up a new era of loosely coupled distributed data exchange.
SOAP Carries an XML RPC tradition by defining an XML language for packaging arbitrarily XML inside an XML envelope. Although SOAP does not depend on HTTP, the momentum behind SOAP is attributable to the fact that HTTP will usually be used for transfer protocol for SOAP messages.
SOAP is a transport protocol similar to IIOP for CORBA, ORPC for DCOM or JRMP for RMI.
SOAP differs from CORBA, RMI or DCOM in several ways.
IIOP, ORPC and JRMP are binary protocols, while SOAP is a text based protocol that uses XML. Using XML for data encoding makes SOAP easier to read than a binary stream.
1) Because SOAP is text based, it is able to move more easily across the firewalls than IIOP, ORPC or JRMP.
<p2) SOAP is based on XML, which is standard driven rather than vendor driven. Potential adaptors are less likely to fear vendor lock in with SOAP. </p2>
The net effect is that SOAP can be picked up by different transport protocol and delivered in different ways. For example, when used with HTTP it can be delivered to a web server, when used over FTP it can be deposited directly into a file system and when used with SMTP it can be delivered to a user's mailbox.
Many companies exchange data between established partners is proving totally satisfactory way to leverage the benefits of XML and the web. In this scenario the required are an agreed upon schema either DTD or an XML schema, for XML data being exchanged and the SOAP server capable of handling the incoming XML as it arrives over the web. Details about what kind of schemau2019s to expect and who will check the XML conforms to the schema are decided offline by individuals participating in the process. On the software side senderu2019s needs to be involved in packaging their data in an XML document. For those companies already storing data in XML, this should require only minimal effort. If the stored XML data is not in the form required by the agreement, an XSL Transformation(XSLT) style sheet can be programmed to automate the transformation.
SOAP messages define one way data transmission from sender to the receiver. However SOAP messages are often combined to implement patterns such as request-response. When using HTTP binding with SOAP, SOAP messages can use the same connection as the inbound request.
Regard's
CHETAN AHUJA
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