Conversational User Interfaces

Self-service systems, online help systems, web services, mobile communication devices, remote control systems, and dashboard computers are providing ever more functionality. However, along with greater functionality, the user must also come to terms with the greater complexity and a steeper learning curve. This complexity is compounded by the sheer proliferation of different systems lacking a standard user interface. Conversational user interfaces allow various natural communication modes like speech, gestures and facial expressions for input as well as output and exploit the context in which an input is used to compute its meaning. The growing emphasis on conversational user interfaces is fundamentally inspired by the aim to support natural, flexible, efficient and powerfully expressive means of human-computer communication that are easy to learn and use. Advances in human language technology and intelligent user interfaces offer the promise of pervasive access to online information and web services. The development of conversational user interfaces allows the average person to interact with computers anytime and anywhere without special skills or training, using such common devices as a mobile phone. Advanced conversational user interfaces include the situated understanding of possibly imprecise, ambiguous or incomplete multimodal input and the generation of coordinated, cohesive, and coherent multimodal presentations. In conversational user interfaces the dialogue management is based on representing, reasoning, and exploiting models of the user, domain, task, context, and modalities. These systems are capable of real-time dialogue processing, including flexible multimodal turn-taking, backchanneling, and metacommunicative interaction. One important aspect of conversations is that the successive utterances of which it consists are often interconnected by cross references of various sorts. For instance, one utterance will use a pronoun to refer to something mentioned in the previous utterance. Computational models of discourse must be able to represent, compute and resolve such cross references. Conversational user interfaces differ in the degree with which the user or the system controls the conversation. In directed or menubased dialogues the system maintains tight control and the human is highly restricted in his dialogue behavior, whereas in free-form dialogue the human takes complete control and the system is totally passive. In mixed-initiative conversational user interfaces, the dialogue control moves back and forth between the system and the user like in most face-to-face conversations between humans. Four papers in this special issue deal with conversational user interfaces that use speech as the main mode of interaction. The paper by Helbig and Schindler discusses state-of-art component technologies and requirements for the successful deployment of conversational user interfaces in industrial environments such as logistics centers, assembly lines, and car inspection facilities. It shows that the speech recognition rate in such environments is still depending on the correct positioning and adjustment of the microphone and discusses the need for wireless microphones in most industrial applications of spoken dialogue systems. Block, Caspari and Schachtl describe an innovative dialogue engine for the Virtual Call Center Agent (ViCA), that provides access to product documentation. A multiframe based dialogue engine is introduced that supports natural conversations by allowing over-answering and free-order information input. The paper reports encouraging results from a usability test showing a high task completion rate. The paper by te Vrugt and Portele describes a tasked-oriented spoken dialogue system that allows the user to control a wide spectrum of infotainment applications, like a hard-disk recorder, an image browser, a music player, a TV set and an electronic program guide. The paper presents a flexible framework for such a multi-application dialogue system and an applicationindependent scheme for dialogue processing. Nöth et al. describe lessons learnt from the implementation of three commercially deployed conversational interfaces. The authors propose five guidelines, which they consider to be crucial, when building and operating telephone-based dialogue systems. One of the guidelines concerns the fact that a spoken dialogue system must react fast to any kind of user input, no matter