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Web Service - the next generation of WWW

Print View , by: iSee ,Total views: 10 ,Word Count: 1885 ,Date: Sun, 24 May 2009 Time: 11:37 AM

Web Service the term seems to heat up overnight. The so-called Web Service is published by the enterprises to complete their particular business needs of the online application service, other companies or application software through the Internet to access and use the online services.
Web Service is the next generation of WWW, which allows Web sites to place in the programmable elements can be Web-based distributed computing and processing. Web Service is moving very quickly, this new specification (SOAP, WSDL and UDDI) to build the module is only a few months before, had been on the design, development and deployment of Web-based applications have had a tremendous impact on the software industry giant and the new Internet era have the software in this area began a new round of competition.

Web Service
The characteristics of
Web Service is packaged as a single entity and published to the network using other programs for the collection of functions. Web Service is used to create an open distributed system component that allows companies and individuals quickly and inexpensively to provide its data services around the world.
Web Service is the core of the next generation of distributed systems, it has the following characteristics:
● Interoperability: Any of the Web Service can be conducted with other Web Service interaction. With SOAP (Simple Object Access Protocol) that all the major suppliers to support the new standard protocols, thus avoiding the CORBA, DCOM and other agreements between the conversion of trouble. But also because you can use any language to write Web Service, so developers need not change their development environment, can the production and use of Web Service.
● universality: Web Service using HTTP and xml to communicate. Therefore, any support for these technologies can have the equipment and access to Web Service.
● easy-to-use: Web Service easier to understand the concept behind, and from IBM and Microsoft this supplier's toll-free kit that allows developers to quickly create and deploy Web Service. In addition, some of the toolbox also allows existing COM components and JavaBean easily become a Web Service.
● industry support: all the major suppliers are in support of SOAP and Web Service technology around. For example, Microsoft's. Net platform based on Web Service, therefore, prepared to use Visual Basic component is easy to deploy as a Web Service and IBM VisualAge can be prepared using the Web Service.
Web Service
Web Service is an independent, modular applications, through networks, in particular the WWW to describe, publish, positioning, and call. Web Service architecture describes three roles (service provider, service requestor, service agent), as well as the three operations (publish, find, bind).
Service providers through the service agent, where to configure and publish the registration service through the lookup service requestor agent services have been published where the registration records to find the service requestor to bind service providers and use the available services.
Web Service in the world, the three operations were praised it contains three different technologies. Published services UDDI (Universal Description, Discovery and Integration), to find services using UDDI and WSDL (Web Service Description Language) a combination of services WSDL binding and SOAP. In three operations, the binding operation is the most important, it contains the actual use of the service, which is prone to interoperability problems. It is because of service provider and service requestor of the full support of the SOAP specification to address these issues and to achieve seamless interoperability.
When the developers to develop new applications, or UDDI Operator through UDDI Search Engine the Web interface in the UDDI Registry to find the needs of Web Service; and then in the UDDI Registry, or through the UDDI Registry to find the Web Service to connect the call to standardize the , the call to use WSDL to describe the general norms. Developers can use development tools or by manually calling the norm, and then add their own applications as defined in the specification called Web Service call. This application developed can be called through SOAP to the Web Service has been designated.
As for the automatic integration of applications with the services (Service) or application (Application), user applications through the SOAP protocol UDDI Operator or visit UDDI Registry, find the Web Service, UDDI Operator and UDDI Registry Agreement through SOAP response Web Service call norms and norms call link, the application has been described using the WSDL specification version of the service call, through the analysis of the description text, automatic generation of a local call interface binding, and the parameters required for proper binding of the call and complete the call.
SOAP Simple Object Access Protocol
SOAP is an XML-based transport protocol does not rely on that layer protocol used between the convenience of the application form to the exchange of data objects. Lower in SOAP, it can be HTTP / HTTP, it could be a SMTP/POP3, also can be applied to a number of specially designed communication protocol specific.
xml in the form of SOAP provides a simple, light-weight for the dispersion or distribution of the environment and type of the exchange of structured information. SOAP itself does not define any application semantics, such as the programming model or a particular realization of the semantic; In fact, it is through the provision of a standard component of the package model and the data encoding module of the mechanism, a simple definition that semantic application mechanism, which can be used from the SOAP messaging systems to RPC.
SOAP consists of three parts:
● SOAP package structure: the definition of an overall framework to show what the contents of the message contains, who is going to deal with these, as well as the content is optional or required.
● SOAP encoding rules: definition of the application for the exchange of data types defined in a series of examples of the mechanism.
● SOAP RPC said: used to indicate the definition of a remote procedure call and response agreements.
In the SOAP package, SOAP encoding rules and outside the SOAP RPC agreement, this specification also defines the two binding agreements, describes the expansion with or without HTTP framework, SOAP message to include in the HTTP message has been sent .
Universal Description,
Discovery and Integration UDDI
UDDI is a Web-based, distributed and provided for the Web Service, the information center for the registration of the realization of standards and norms, but also enable enterprises to set their own registration to provide the Web Service to enable other businesses to find the the realization of the standard access protocol.
UDDI is a core component of UDDI Business Registry, which uses an xml document to describe the business and provide the Web Service. Conceptually, UDDI business registration information provided consists of three parts:
● White (White Page): including the address, contact methods and known business logos.
● Yellow Pages (Yellow page): including the standard classification based on the types of trades.
● Green Page (Green Page): including on the corporate Web Service provided technical information in the form may be some point to a file or URL of the target, and these documents or URL is the service discovery mechanism for services.
All of the UDDI Business Registry information is stored in the UDDI Business Registry. Through the use of UDDI discovery services, enterprises can be registered by other companies who wish to found their own to provide the Web Service. Commercial enterprises through UDDI registry Web interface, or use a "UDDI Programmer's API standard" programming interface described in the tools, information added to the UDDI Business Registry. UDDI Business Registry is a logically centralized, physically distributed by a number of root composition, among the rules according to a certain data synchronization. When a commercial Enterprise in the UDDI registry to implement an example of registration, the registration information will be automatically copied to the other UDDI root, so any hope can be found by Web Service found that the people.
Web Services Description Language WSDL
With the communication protocol and message format in the Web of standardized, formatted in some way to describe the communication is becoming increasingly important, the possibility of its realization is also growing. WSDL definition with a set of XML grammar to describe the network of services to meet this demand. WSDL definition of the network services can exchange messages as a communication endpoint set. WSDL services provided for the distributed system to help document, while the service automatically can also be used as inter-application communication solutions.
Services of a WSDL document is defined as a collection of network endpoints, or ports collection. In WSDL, the abstract endpoint, and the definition of news with their specific network and data format is separated from binding. This allows reuse of abstract definitions: messages, the need for data exchange described in the abstract; port type, an abstract collection of operations. Port for a specific type of specific protocols and data formats norms constitute a reusable binding. The definition of a port into a network address and the binding of reusable connections, defined as a collection of port services. Therefore, the definition of a WSDL document in the use of network service elements are as follows:
● Type: the use of certain types of systems (such as XSD) data type definition.
● news: communication data has the type of abstract definitions.
● operations: service support of the abstract description of the action.
● Port Type: an abstract collection of operations, the operation by one or more endpoint support.
● bind: port for a specific type of concrete protocol specification and data format specification.
● Port: a single endpoint, defined as a binding and a network connection address.
● Service: a collection of related endpoints.

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