Vector-based Natural Language Call Routing

This paper describes a domain-independent, automatically trained natural language call router for directing incoming calls in a call center. Our call router directs customer calls based on their response to an open-ended How may I direct your call? prompt. Routing behavior is trained from a corpus of transcribed and hand-routed calls and then carried out using vector-based information retrieval techniques. Terms consist of n-gram sequences of morphologically reduced content words, while documents representing routing destinations consist of weighted term frequencies derived from calls to that destination in the training corpus. Based on the statistical discriminating power of the n-gram terms extracted from the caller's request, the caller is 1) routed to the appropriate destination, 2) transferred to a human operator, or 3) asked a disambiguation question. In the last case, the system dynamically generates queries tailored to the caller's request and the destinations with which it is consistent, based on our extension of the vector model. Evaluation of the call router performance over a financial services call center using both accurate transcriptions of calls and fairly noisy speech recognizer output demonstrated robustness in the face of speech recognition errors. More specifically, using accurate transcriptions of speech input, our system correctly routed 93.8% of the calls after redirecting 10.2% of all calls to a human operator. Using speech recognizer output with a 23% error rate reduced the number of correctly routed calls by 4%.