VXML(Voice XML) is widely used by IVR users who prefer to host their voice applications with hosted IVR provider. Mostly, companies or organizations who want to have their complete control on the voice application and do not want to invest in CTI hardware and infrastructure of running a data center along with telephone lines.
In simple and plain language, VXML based applications remain at IVR user premise and hosted IVR system downloads VXML codes to its server and executes the codes. By this arrangement, VXML based voice applications remain at the control of the IVR user while users of that voice application call up hosted IVR number and avail the IVR service.
Payment gateway, CRM ( Customer Resource Management) are few IVR applications which are widely configured to work in the above architecture.
Though VXML is preferred tool for writing such voice applications, as it works seamlessly with any web services as well as its similarity in coding with HTML. Now a days, many hosted IVR service providers provide visual tools for developing voice applications which are faster and simpler to learn and develop any kind of voice applications.
Main advantages of use of VXML for voice application to be hosted are :-
1. VXML is standard adopted by W3C and now supported by all hosted IVR providers. It provides flexibility to change its call flow locally without having to depend on hosted IVR provider.
2. Many high end PABX systems supports VXML now a days. There are large community who are actively developing VXML based voice applications.
3. VXML offers very high flexibility in terms of distributed computing as VXML codes may reside in many web servers which would be fetched by hosted IVR server. New VXML voice applications could be stored in different server anytime without any changes in hosted IVR platform.
4. Adopting new technologies like automatic speech recognition (ASR), text to speech conversion ( TTS) and other CTI technologies are easy for VXML based voice applications.
Though VXML provides many advantages, it has some disadvantages too:-
1. VXML interpreter introduces new cost of total IVR system which may increase cost of the IVR system.
2. It is not that easy to write voice applications using VXML and to maintain it, trained VXML coders are required full time.
3. There are many hosted IVR service providers who do not support VXML due to cost component. Other alternatives to VXML, visual tools like INVOX come with free for hosted IVR subscriber and much easier to develop voice applications.
So, for voice applications which need to be tightly integrated with other web services, VXML seems to a good choice while quick changes in call flow, visual tool for designing call flow seems better choice.