Web services standards :
The following standards play key roles in Web services: Universal Description, Discovery and Integration (UDDI), Web Services Description Language (WSDL), SOAP, and eXtensible Markup Language (XML).
Universal Description, Discovery and Integration (UDDI) :
UDDI is a protocol for describing available Web services components.The specification defines a group of Web services and programmatic interfaces for publishing, retrieving, and managing information about services. (In true SOA fashion, a UDDI registry is itself composed of Web services!) UDDI builds upon several other established industry standards, including HTTP, XML, XML Schema (XSD), SOAP, and WSDL.
A UDDI registry contains categorized information about businesses and the services that they offer, and it associates those services with technical specificiations of the Web Service. These technical specifications are usually defined using WSDL.A Web Service consumer queries the UDDI registry to find the WSDL descriptions to determine how to use the Web Service.The UDDI Project operates a global public registry called the UDDI Business Registry. This registry is available to everyone at no charge (see http://www.uddi.org) ).Before you can publish your business entity and Web service to a public registry, you must first register your business entity with a UDDI registry.
Organizations can also set up a private registry to support the requirements of an enterprise or a private community.A private registry allows you to publish and test your internal applications in a secure, private environment.
Web Services Description Language (WSDL):
WSDL describes web services in XML format.Since XML is used so WSDL is plateform and language independant.
WSDL allows a service provider to specify the following characteristics of a Web service:
WSDL specification(which is in XML) divided into six major elements - Definition, Types, Message, PortType, Service
Simple Object Access Protocol(SOAP):
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.SOAP has
Other frameworks existed which provided SOAP like functionalitiy e.g. CORBA, DCOM and Java RMI. Since SOAP is written entirely in XML so it is platform and language independent unlike other frameworks.
eXtensible Markup Language (XML) :
XML is an eXtensible Mark-up Language that enables you to identify and organize your information in a more accurate and flexible way. It is called extensible because it does not have a fixed format. An example of a mark-up language that has a fixed format is HTML. The difference between the two is that with XML you can define any element and call it whatever you like, while with HTML you already have pre-defined elements and attributes. For instance, to make text appear italic in a Web browser, you use the tags. Every modern browser knows how to display that text. Without pre-defined tags like this, XML allows you to define your own tags to both display and format text. This flexibility is exactly what Web services use to make it both platform and implementation independent.
The following standards play key roles in Web services: Universal Description, Discovery and Integration (UDDI), Web Services Description Language (WSDL), SOAP, and eXtensible Markup Language (XML).
Universal Description, Discovery and Integration (UDDI) :
UDDI is a protocol for describing available Web services components.The specification defines a group of Web services and programmatic interfaces for publishing, retrieving, and managing information about services. (In true SOA fashion, a UDDI registry is itself composed of Web services!) UDDI builds upon several other established industry standards, including HTTP, XML, XML Schema (XSD), SOAP, and WSDL.
A UDDI registry contains categorized information about businesses and the services that they offer, and it associates those services with technical specificiations of the Web Service. These technical specifications are usually defined using WSDL.A Web Service consumer queries the UDDI registry to find the WSDL descriptions to determine how to use the Web Service.The UDDI Project operates a global public registry called the UDDI Business Registry. This registry is available to everyone at no charge (see http://www.uddi.org) ).Before you can publish your business entity and Web service to a public registry, you must first register your business entity with a UDDI registry.
Organizations can also set up a private registry to support the requirements of an enterprise or a private community.A private registry allows you to publish and test your internal applications in a secure, private environment.
Web Services Description Language (WSDL):
WSDL describes web services in XML format.Since XML is used so WSDL is plateform and language independant.
WSDL allows a service provider to specify the following characteristics of a Web service:
- The name of the Web service and addressing information
- The protocol and encoding style to be used when accessing the public operations of the Web service
- The type information such as operations, parameters, and data types comprising the interface of the Web service
- WSDL documents allow developers to expose their applications as network-accessible services on the Internet. Through UDDI and WSIL, other applications can discover WSDL documents and bind with them to execute transactions or perform other business processes.
WSDL specification(which is in XML) divided into six major elements - Definition, Types, Message, PortType, Service
Simple Object Access Protocol(SOAP):
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.SOAP has
Other frameworks existed which provided SOAP like functionalitiy e.g. CORBA, DCOM and Java RMI. Since SOAP is written entirely in XML so it is platform and language independent unlike other frameworks.
eXtensible Markup Language (XML) :
XML is an eXtensible Mark-up Language that enables you to identify and organize your information in a more accurate and flexible way. It is called extensible because it does not have a fixed format. An example of a mark-up language that has a fixed format is HTML. The difference between the two is that with XML you can define any element and call it whatever you like, while with HTML you already have pre-defined elements and attributes. For instance, to make text appear italic in a Web browser, you use the tags. Every modern browser knows how to display that text. Without pre-defined tags like this, XML allows you to define your own tags to both display and format text. This flexibility is exactly what Web services use to make it both platform and implementation independent.
Web services Model:
Web services can be classified as “Big” web services and “RESTful” web services. Big web services are based on SOAP standard.RESTful web services are based on the way how our web works ( world wide web / www). I my next blog we will see the details about Web services types.
