The next generation of distributed computing has arrived. A Web service is a unit of managed code that can be remotely invoked using HTTP, that is, it can be activated using HTTP requests.
Historically speaking, remote access to binary units required platform-specific and sometimes language-specific protocols. For example, DCOM clients access remote COM types using tightly coupled RPC calls. CORBA requires the use of tightly coupled protocol referred to as Internet Inter-ORB Protocol (IIOP), to activate remote types. Enterprise JavaBeans (EJBs) requires a Remote Method Invocation (RMI) Protocol and by and large a specific language (Java). Thus each of these remote invocation architectures needs proprietary protocols, which typically require a tight connection to the remote source.
One can access Web services using nothing but HTTP. Of all the protocols in existence today, HTTP is the one specific wire protocol that all platforms tend to agree on. Thus , using Web services, a Web service developer can use any language he wish and a Web service consumer can use standard HTTP to invoke methods a Web service provides. The bottom line is that we have true language and platform integration . Simple Object Access Protocol (SOAP) and XML are also two key pieces of the Web services architecture.
What is a Web Service
Web services constitute a distributed computer architecture made up of many different computers trying to communicate over the network to form one system. They consist of a set of standards that allow developers to implement distributed applications - using radically different tools provided by many different vendors - to create applications that use a combination of software modules called from systems in disparate departments or from other companies.
A Web service contains some number of classes, interfaces, enumerations and structures that provide black box functionality to remote clients. Web services typically define business objects that execute a unit of work (e.g., perform a calculation, read a data source, etc.) for the consumer and wait for the next request. Web service consumer does not necessarily need to be a browser-based client. Console-baed and Windows Forms-based clients can consume a Web service. In each case, the client indirectly interacts with the Web service through an intervening proxy. The proxy looks and feels like the real remote type and exposes the same set of methods. Under the hood, the proxy code really forwards the request to the Web service using standard HTTP or optionally SOAP messages.
Web Service Standards
Web services are registered and announced using the following services and protocols. Many of these and other standards are being worked out by the UDDI project, a group of industry leaders that is spearheading the early creation and design efforts.
Universal Description, Discovery, and Integration (UDDI) is a protocol for describing available Web services components. This standard allows businesses to register with an Internet directory that will help them advertise their services, so companies can find one another and conduct transactions over the Web. This registration and lookup task is done using XML and HTTP(S)-based mechanisms.
Simple Object Access Protocol (SOAP) is a protocol for initiating conversations with a UDDI Service. SOAP makes object access simple by allowing applications to invoke object methods or functions, residing on remote servers. A SOAP application creates a request block in XML, supplying the data needed by the remote method as well as the location of the remote object itself.
Web Service Description Language (WSDL), the proposed standard for how a Web service is described, is an XML-based service IDL (Interface Definitition Language) that defines the service interface and its implementation characteristics. WSDL is referenced by UDDI entries and describes the SOAP messages that define a particular Web service.
ebXML (e-business XML) defines core components, business processes, registry and repository, messaging services, trading partner agreements, and security.
Implementing Web Services
Here comes a brief step-by-step on how a Web service is implemented.
* A service provider creates a Web service
* The service provider uses WSDL to describe the service to a UDDI registry
* The service provider registers the service in a UDDI registry and/or ebXML registry/repository.
* Another service or consumer locates and requests the registered service by querying UDDI and/or ebXML registries.
* The requesting service or user writes an application to bind the registered service using SOAP in the case of UDDI and/or ebXML
* Data and messages are exchanged as XML over HTTP
Web Service Infrastructure
Source:
http://www.roseindia.net/webservices/webservices.shtml
Historically speaking, remote access to binary units required platform-specific and sometimes language-specific protocols. For example, DCOM clients access remote COM types using tightly coupled RPC calls. CORBA requires the use of tightly coupled protocol referred to as Internet Inter-ORB Protocol (IIOP), to activate remote types. Enterprise JavaBeans (EJBs) requires a Remote Method Invocation (RMI) Protocol and by and large a specific language (Java). Thus each of these remote invocation architectures needs proprietary protocols, which typically require a tight connection to the remote source.
One can access Web services using nothing but HTTP. Of all the protocols in existence today, HTTP is the one specific wire protocol that all platforms tend to agree on. Thus , using Web services, a Web service developer can use any language he wish and a Web service consumer can use standard HTTP to invoke methods a Web service provides. The bottom line is that we have true language and platform integration . Simple Object Access Protocol (SOAP) and XML are also two key pieces of the Web services architecture.
What is a Web Service
Web services constitute a distributed computer architecture made up of many different computers trying to communicate over the network to form one system. They consist of a set of standards that allow developers to implement distributed applications - using radically different tools provided by many different vendors - to create applications that use a combination of software modules called from systems in disparate departments or from other companies.
A Web service contains some number of classes, interfaces, enumerations and structures that provide black box functionality to remote clients. Web services typically define business objects that execute a unit of work (e.g., perform a calculation, read a data source, etc.) for the consumer and wait for the next request. Web service consumer does not necessarily need to be a browser-based client. Console-baed and Windows Forms-based clients can consume a Web service. In each case, the client indirectly interacts with the Web service through an intervening proxy. The proxy looks and feels like the real remote type and exposes the same set of methods. Under the hood, the proxy code really forwards the request to the Web service using standard HTTP or optionally SOAP messages.
Web Service Standards
Web services are registered and announced using the following services and protocols. Many of these and other standards are being worked out by the UDDI project, a group of industry leaders that is spearheading the early creation and design efforts.
Universal Description, Discovery, and Integration (UDDI) is a protocol for describing available Web services components. This standard allows businesses to register with an Internet directory that will help them advertise their services, so companies can find one another and conduct transactions over the Web. This registration and lookup task is done using XML and HTTP(S)-based mechanisms.
Simple Object Access Protocol (SOAP) is a protocol for initiating conversations with a UDDI Service. SOAP makes object access simple by allowing applications to invoke object methods or functions, residing on remote servers. A SOAP application creates a request block in XML, supplying the data needed by the remote method as well as the location of the remote object itself.
Web Service Description Language (WSDL), the proposed standard for how a Web service is described, is an XML-based service IDL (Interface Definitition Language) that defines the service interface and its implementation characteristics. WSDL is referenced by UDDI entries and describes the SOAP messages that define a particular Web service.
ebXML (e-business XML) defines core components, business processes, registry and repository, messaging services, trading partner agreements, and security.
Implementing Web Services
Here comes a brief step-by-step on how a Web service is implemented.
* A service provider creates a Web service
* The service provider uses WSDL to describe the service to a UDDI registry
* The service provider registers the service in a UDDI registry and/or ebXML registry/repository.
* Another service or consumer locates and requests the registered service by querying UDDI and/or ebXML registries.
* The requesting service or user writes an application to bind the registered service using SOAP in the case of UDDI and/or ebXML
* Data and messages are exchanged as XML over HTTP
Web Service Infrastructure
Source:
http://www.roseindia.net/webservices/webservices.shtml
