A VoiceXML IVR application operates like a traditional web application. However, instead of a web browser presenting an HTML-based web page generated by a web server that in turn asks for data from a database, a VoiceXML IVR plays a VXML-based dialog. VoiceXML takes the place of HTML in this example, and basically allows the application to function in the same way. This could be analogous to ordering food in a restaurant. The waiter presents a menu of choices, and after perusing the menu, you settle on your preference and communicate your choice to the waiter. The waiter takes your order, but they are not responsible for cooking your food. Instead, your order is submitted to the cook, who then assembles various ingredients, and combines them to make your meal. The waiter then picks up your dishes, brings them to the table, and serves you.
Now instead, imagine an IVR server, a call flow application server, a business logic server, and a database. The call flow app server tells the IVR what to say and what to collect from the caller. The caller enters their information over the phone, and the IVR delivers this information to a call flow app server. The call flow app server, however, does not know what data is associated with the information it has just received, so it has to ask the business logic server for this data. The business logic server knows how to extract data from the database. After the business logic server determines this value, it is relayed to the call flow app server. The call flow app server then builds a VoiceXML script that will instruct the IVR server to verbalize your data. We refer to this as the VoiceXML IVR four-tier architecture. Plum Voice builds the IVR platform (tier one) from the ground up, and we specialize in writing custom call flow application server code (tier two). Typically, customers provide tiers three and four on their own, as they already own web servers and databases that suit these two roles respectively. In general, customers typically write the business logic server code as they have the most knowledge of how their business processes work, and how their business data is structured.
