296 CHAPTER 8 Enterprise application testing indicating that the product is available in inventory and a ship date has been scheduled. This is known as a "bi-directional" real-time integration. All of these integrations can be direct system-to-system integrations, but most large enterprises have moved away from this approach. Is it far more common for yet another enterprise application to be put in place as an integration solution. The logic behind this is that multiple enterprise applications may need to have integrations to the same back-end systems. With a system-to-system integration, any time the back-end system changes, all of the connecting applications need to be modified as well. With an enterprise integration solution in place, it is often sufficient to simply make changes within the integration application and leave the application using the interface alone. 8.2.3.1.1 Web services In some cases, real-time integration applications require the use of proprietary protocols or agent software. However, more and more interfaces are being built to use web services either as part of a service-oriented architecture or simply to increase ease-of-use of the interface. Web services are integrations based on a number of standards such as Extensible Markup Language (XML), Simple Object Access Protocol (SOAP), and Web Services Description Language (WSDL) in such