What is the SOAP ??

05 Jan

SOAP is a protocol specification to invoke methods on servers, services, components and objects. The available procedure of using XML and HTTP as a method invocation mechanism is implied by SOAP. A small number of HTTP headers that facilitate firewall/proxy filtering are authorized by the SOAP specification. The SOAP specification also mandates an XML vocabulary that is used to represent method parameters, return values, and exceptions.

To exchange structured and typed information between peers in a decentralized, distributed environment using XML, SOAP presents an uncomplicated mechanism. SOAP defines a simple mechanism for expressing application semantics by providing a modular packaging model and encoding mechanisms for encoding data within modules instead of defining any application semantics such as a programming model or implementation specific semantics. This allows SOAP to be used in a large variety of systems ranging from messaging systems to RPC.

An Overview to SOAP

SOAP, (the Simple Object Access Protocol), is XML syntax to exchange messages. Moreover, since it is XML, it is independent from both language and platform. In addition, SOAP is a fundamental part of .NET, Microsoft’s new development platform, and to understand what SOAP is and how it works it will be important for developers to move towards .NET.

In SOAP, there are four parts:

  • The SOAP envelope construct: Defines an overall framework to express what is in a message, who should deal with it, and whether it is optional or mandatory.
  • The SOAP encoding rules: Defines a serialization mechanism that can be used to exchange instances of application-defined datatypes.
  • The SOAP RPC representation: Defines a convention that can be used to represent remote procedure calls and responses.
  • The SOAP binding: Defines a convention to exchange SOAP envelopes between peers using an underlying protocol for transport.

Simply, SOAP is a well-documented wire protocol. Microsoft is getting behind SOAP and in future, probably will offer some type of implementation. However, other vendors can also do the same. For instance, the Perl implementation of SOAP is not tied to COM or Windows in any way, and if a modern version of Perl is available, can be used on any platform where. SOAP does not attach anyone to a particular platform. It provides a practical way to communicate over the Internet that is easy to implement on any platform.

Functionally, SOAP is very similar to IIOP which the underlying protocol used by most CORBA products. DCOM has additional protocol functionality such as garbage collection, causality that is not present in IIOP or SOAP. However, DCOM’s extended functionality generally only needed in server-server communications and is not required in client-server communications. An advantage of both IIOP and DCOM side, SOAP packets be likely to be larger on the wire and can be somewhat more resource intensive to parse/generate.


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Posted by on January 5, 2012 in ASP .NET


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