Think of Web Services as Software Lego. Just as Lego blocks can be assembled together to build bigger structures, Web Services provide a mechanism to integrate programming modules from different companies and across the Web to build network-wide applications. Web Services offers a vision where computer systems can talk to each other in real-time without building connectors for every new connection (application) needs to be added.
While there have been services like EDI in the past, it has not been possible to build these applications on a much larger scale and across enterprises cost-effectively. What Web Services does is offer a platform through a set of standards to enable this across silos of information and systems within and across enterprises. It is part of the movement where software is no shrink-wrapped or built to custom-specifications, but rather pieced together on demand from pre-fabricated components on the Internet.
Here is a collection of views which help explain the concept and vision of Web Services.
Leslie Walker (Washington Post):
The grand idea is to make Internet software more interoperable by agreeing to common communication conventions that would allow disparate programs to snap together like Lego blocks. Web services are the hoped-for byproduct of a new set of standards being developed for Internet softwarewhich supposedly will help programmers create smarter services online, in part by spawning software “agents” that will do work people now do manually by surfing to various Web sites.
Kevin Werbach (Release 1.0):
Web services are software objects that can be assembled over the Internet using standard protocols to perform functions or execute business processes. They fill in the white space between applications, systems and companies with simple messaging, description, discovery and management protocols and other mechanisms.
Anything can be exposed as a Web service, from trivial Fahrenheit-to-Celsius temperature converters to full enterprise applications. To use what is fast becoming a canonical example, the provider of an online portfolio application could call a stock-quote service over the Internet using an open format, rather than hard-coding in the feed. It could use the same mechanism to add other services or swap out quote providers, because everything uses the same protocols.
Web services seek to realize a widely shared vision for the future of software: distributed, componentized, standardized, open, scalable, and Internet-centric.
An IBM White Paper:
Web Services has been described as a new computing model for using the Web – the building blocks allowing companies and individuals to quickly and inexpensively make their digital assets available worldwide. Until now, users have used the Web to browse for information, download files and initiate purchases and transactions. All of these activities are performed manually by way of a browser. Web Services are Internet-based applications that perform a specific task or set of tasks. Web Services are initiated automatically by a program or set of programs.
One B-to-C example is the Web Service that executes a program from a PC, PDA, Internet phone, etc. and goes out to various Internet sites, accesses a user’s financial data – a Chase Manhattan checking account, a Fidelity investment portfolio, an IBM 401K statement, a CD from BankOne and savings account from Bank of America – into one consolidated statement. Browsers can’t do that; Web Services can!
One B-to-B example is the Web Service that allows application integration beyond the boundary of the enterprise, tieing the workflow, the processes, all the approval and the actual application integration from one partner to a supplier to another partner together to enable business to be conducted as a group of partnerships.