Web services, where software connects to other service-generating software, is seen as a critical ingredient of the next generation of the web, now referred to as Web 2.0. Key to web services technology is WSDL, an XML vocabulary for describing web services. Web service providers make WSDL descriptions available that allow programs to connect to and use the services. Currently, web services utilize SOAP or REST (or both) for their infrastructure. Numerous tools exist that facilitate the definition, deployment, and access of web services. In the realm of software architecture, web services are being used to develop loosely coupled service-oriented architectures (SOAs).