Web Services are receiving a lot of press attention. Some are heralding Web Services as the biggest technology breakthrough since the web itself; others are more skeptical that they are nothing more than evolved web applications.
A Web Service is a collection of functions that are packaged as a single entity and published to the network for use by other programs. Web services are building blocks for creating open distributed systems, and allow companies and individuals to quickly and cheaply make their digital assets available worldwide. One early example is Microsoft Passport, but many others such as Project Liberty are emerging. One Web Service may use another Web Service to build a richer set of features to the end user. Web services for car rental or air travel are examples. In the future applications may be built from Web services that are dynamically selected at runtime based on their cost, quality, and availability.
The power of Web Services comes from their ability to register themselves as being available for use using WSDL (Web Services Description Language) and UDDI (Universal Description, Discovery and Integration). Web services are based on XML (extensible Markup Language) and SOAP (Simple Object Access Protocol).
Despite whether you see the difference between sophisticated web applications and Web Services, it is clear that these emerging systems will face the same security issues as traditional web applications.