Explain SOAP Web Services ?
SOAP is an acronym for Simple Object Access Protocol. SOAP web services are loosely coupled because the consumer, of a web service does not know its implementation details. The consumer is able to invoke a SOAP web service using a self-explanatory interface describing the available business methods. The underlying implementation can be done in any language. A consumer and a service provider exchange data in a loosely coupled way using XML documents. A consumer sends a request to a SOAP web service in the form of an XML document, and receives a reply, also in XML.
SOAP web services are also about distribution. HTTP is the default network protocol, And it is a well-known and robust stateless protocol. SOAP web services are everywhere. They can be invoked from a simple desktop or used for business-to-business
(B2B) integration. SOAP web services integrate applications run by different systems through the Internet or within the same company
which is known as Enterprise Application Integration, or EAI. In all types of cases, they give a standard way of connection.
SOAP web services constitute a type of business logic exposed via a service i.e., the service provider to a client i.e., the service consumer. However, unlike objects or EJBs, SOAP web services provide a loosely coupled interface using XML. SOAP web service standards specify that the interface to which a message is sent should define
the format of the message request and response, and mechanisms to publish and to discover web service interfaces (the service registry).
The SOAP web service can optionally register its interface into a registry (Universal Description Discovery and Integration, or UDDI) so a consumer can discover it. Once the consumer knows the interface of the service and the message format, it can send
a request to the service provider and receive a response.
SOAP web services depend on several technologies and protocols :
XML
Extensible Markup Language is the basic foundation on which SOAP web services are built and defined (SOAP, WSDL, and UDDI).
WSDL
Web Services Description Language defines the message types, interface, protocol and interactions between the consumer and the provider.
SOAP
Simple Object Access Protocol is a message-encoding protocol based on XML technologies, defining an envelope for web services communication.
Messages
Messages are exchanged using a transport protocol. Although Hypertext Transfer Protocol (HTTP) is the most widely adopted transport protocol, others such as SMTP or JMS can also be used.
UDDI
Universal Description Discovery, and Integration is an optional service registry and discovery mechanism, it can be used for storing and categorizing SOAP web services interfaces (WSDL).
With these standard technologies, SOAP web services provide almost infinite potential. Clients can call a service, which can be mapped to any program and accommodate any data type and structure to exchange messages through XML.
