SOAP - Enabling communicationby Aswathi P P (Software Programmer, Excellone Technologies)
Simple Object Access Protocol [SOAP] is an extensible,
text-based framework for enabling communication between diverse
parties- i.e. objects that have no prior knowledge of each other
or of each others platforms in the web technology field. This XML-based
object invocation protocol was first incorporated for distributed
applications to interact over HTTP and through corporate firewalls.
Client applications can inter-operate in loosely coupled environments
to discover and connect dynamically to services without having any
agreements established between them previously.
Message Format
The standardized message format has a MIME type
of "text/xml" and the soap envelope. The envelope, which is an XML
document, consists of a header (optional) and a body (mandatory).
Header entries are for the modes that perform intermediate processing
while the body part is focused on the final recipient of the message.
Name Spaces
First name space defines the
elements and attributes in this message. Second name space refers
to the SOAP encoding which is applicable to the whole document.
Head
The transaction element comes
first along with name space attributes and by the must Understand
attribute with a value of 1. The header processing is entirely independent
of the SOAP message body. Other than defining transaction modes
like intermediate notes, a SOAP message may optionally contain header
entries specifying nodes that perform authorization processing,
encryption, persistence of state, business logic processing etc.
Body
The cryptic and modular packaging
model SOAP body consists of a XML payload, which we can service.
SOAP-RPC
Usually follows one-way transmissions
from a sender to a receiver. SOAP messages do have to be combined
to implement request response mechanisms. While using SOAP-RPC,
first of all the request and response message must be encoded as
structures. In each input parameter of an operation there must be
an element with the same name as parameter. Also every output parameter
must contain an element with a matching name.
A SOAP client
A program that creates an XML document containing
the information required to invoke remotely a method in a distributed
system is known as a SOAP client. As requests and messages are sent
over HTTP, SOAP documents enable the transfer of information across
divergent web platforms.
A SOAP server
A SOAP server is a special code that listens for
SOAP messages and acts as a distributor and interpreter of SOAP
documents.
In conclusion
This XML based protocol for sending messages and
making remote procedure calls in a distributed environment that
contains 3 parts. The SOAP envelope construct defining an over-all
framework for defining the content of the message, the concerned
person to deal with it and whether it is mandatory or optional.
The encoding rules define a serialization mechanism used to exchange
instances of application-defined data-types. The SOAP RPC, defines
a connection that can be used to exchange instance of application-defined
data-types.
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