Introducing Web Services
- The Basics of Web Services
- A Simple Example: Searching for Information
- The Next Generation of the Web
- Interacting with Web Services
- The Technology of Web Services
- XML for Business Collaboration: ebXML
- Web Services versus Other Technologies
- Additional Technologies
- Vendor Approaches to Web Services
Like the effect of rail transportation on national economic systems, Web services are fundamentally changing the rules of Web commerce. They connect programs to each other across distant points on the global map, transporting large amounts of data more efficiently and cheaply than ever before. The result is faster, better, and more productive communication for businesses and consumers alike.
The Web started out supporting human interactions with textual data and graphics. People use the Internet daily to look up stock quotes, buy consumer goods, and read the latest news. This level of interaction is fine for many purposes. But the essentially text-based Web does not support software interactions very well, especially transfers of large amounts of data. A more efficient method is needed that allows applications to interact directly with one another, automatically executing instructions that would otherwise have to be entered manually through a browser.
Individuals and companies doing business over the Web need a way to publish links to their applications and data, in much the same way that they publish links to their Web pages. Internet-based applications need to be able to find, access, and automatically interact with other Internet-based applications. Web services improve Internet use by enabling program-to-program communication. Through the widespread adoption of Web services, applications at various Internet locations can be directly integrated and interconnected as if they were part of a single, large IT (information technology) system.
The Basics of Web Services
Web services are Extensible Markup Language (XML) applications mapped to programs, objects, or databases or to comprehensive business functions. Using an XML document created in the form of a message, a program sends a request to a Web service across the network, and, optionally, receives a reply, also in the form of an XML document. Web services standards define the format of the message, specify the interface to which a message is sent, describe conventions for mapping the contents of the message into and out of the programs implementing the service, and define mechanisms to publish and to discover Web services interfaces.
This technology can be used in many ways. Web services can run on desktop and handheld clients to access such Internet applications as reservations systems and order-tracking systems. Web services can also be used for business-to-business (B2B) integration, connecting applications run by various organizations in the same supply chain. Web services can also solve the broader problem of enterprise application integration (EAI), connecting multiple applications from a single organization to multiple other applications both inside and outside the firewall. In all these cases, the technologies of Web services provide the standard glue connecting diverse pieces of software.
As illustrated in Figure 1-1, Web services present to the networks a standard way of interfacing with back-end software systems, such as database management systems, .NET, J2EE (Java2 Platform, Enterprise Edition), or CORBA (common object request broker architecture), objects, adapters to enterprise resource planning (ERP) packages, integration brokers, and others. Web services interfaces receive a standard XML message from the networking environment, transform the XML data into a format understood by a particular back-end software system, and, optionally, return a reply message. The underlying software implementations of Web services can be created by using any programming language, operating system, or middleware system.
Figure 1-1 Web services interface with back-end systems
Web services combine the execution characteristics of programmatic applications with the abstraction characteristics of the Internet. Today's Internet technologies succeed in part because they are defined at a sufficiently high level of abstraction to enable compatibility with any operating system, hardware, or software. The Web services-based Internet infrastructure exploits this abstraction level and includes semantic information associated with data. That is, Web services define not only the data but also how to process the data and map it into and out of underlying software applications.