Essentials of SOA, Web Services and ESB in the Integration context – Part II
According to W3, “Web services architecture is an interoperability architecture that provides a standard means of interoperating between different software applications, running on a variety of platforms and/or frameworks”.
The core technologies used for Web services are:
- XML: generic language that can describe any kind of content in a structured way, separated from its presentation to a specific device.
- SOAP: Platform-neutral protocol that allows a client to call a remote service.
- WSDL: XML-based interface and implementation description language. Using a WSDL document, the service provider specifies the operations that a Web service provides and the parameters and data types of these operations.
- UDDI: Universal Description, Discovery, and Integration (UDDI) is both a client-side API and a SOAP-based server implementation used to store and retrieve information about service providers and Web services.
- WSIL: Web Services Inspection Language (WSIL) is an XML-based specification that locates Web services without using UDDI.
Web services have the following key properties:
- Web services are self-contained. On client side, no additional software required. On server side, an HTTP and SOAP server would suffice;
- Web services are self-describing; Format definition travels with the service – no metadata repository required.
- Web services can be published, located, and invoked across the Web;
- Web services are language-independent and interoperable;
- Web services are loosely coupled;
- Web services are dynamic; With UDDI and WSDL, the discovery is automated and Web services can be deployed without disturbing the clients.
- Web services provide programmatic access; Service consumers have to know the interfaces to Web Services and no knowledge of implementation required.
Web services alone cannot handle the complex requirement of SOA within an enterprise. That is where ESB – the Enterprise Service Bus – seen as the Universal Integration Backbone comes in.