Web Services: W3C Definition A Web service is a software system Identified by a URL, whose public interfaces and bindings are defined and described using XML Its definition can be discovered by other software systems These systems may then interact with the Web service using XML based messages conveyed by Internet protocols
Web Services Web services are an emerging technology that offer a solution for providing a common collaborative architecture Web services provide functional building blocks which are not tied to any particular programming language or hardware platform They are accessible over standard Internet protocols
The Evolution Online systems replace Batch systems Graphical User Interfaces replace “green” screens Networked systems replace standalone systems Internet based systems replace LAN based systems Future ??? Web Services replace simple Internet and LAN based systems
Web Services Technologies XML (eXtensible Markup Language) markup language that underlies most of the specifications used for Web services SOAP (Simple Object Access Protocol) (Simple Object Access Protocol), similar to JDBC, is a network, transport, and programming language and platform neutral protocol that allows a client to call a remote service. The message format is XML. WSDL (Web services description language) An XML-based interface and implementation description language. The service provider uses a WSDL document in order to specify the operations a Web service provides. UDDI (universal description, discovery, and integration) Both a client-side API and a SOAP-based server implementation that can be used to store and retrieve information on service providers and Web services.
How it works A Web Service is a URL-addressable software resource that performs functions (or a function) Web Services communicate using standard protocol known as SOAP (Simple Object Access Protocol) A Web Service is located by its listing in a Universal Discovery, Description and Integration (UDDI) directory
Web Services Integration In a lot of organizations, the data and logic of one application are basically useless to other applications When an application and its data are isolated from other applications, we often say that they are in “silos” Web Services are better at sharing data and functions The result is that the “silos” come down, and previously isolated systems can talk to each other
Web Services Access Web Services are especially good at providing access through different interfaces A Web Service can have a dedicated client application, but it can also be readily accessed through browsers, wireless devices, voice-activated interfaces, and so on Adding new access methods is much simpler than with a traditional application
Web Services Flexibility One of the more important innovations in Web Services is “machine-to-machine communications” This means that a Web Service can ask another Web Service to do something, and that Web Service can ask another Web Service to do something, and so on In the future, many Web Services will really just be aggregations of other Web Services
Web Services Application Assembly Future applications will be assembled from a diverse group of web services, aggregating functionality Reusability is extended to the execution level, versus reusability from just the design and construction level
SOAP Simple Object Access Protocol SOAP is an open protocol specification defining a uniform way of performing RPCs using HTTP as the underlying communications protocol with XML for the data serialization.
How Is a Service Described? WSDL (Web Service Description Language) XML-based W3C for standard
How Do I Find Web Services? UDDI project by Microsoft, IBM, and others Take a look at uddi.org Websites //www.xmethods.net //www.salcentral.com