ECAF: Authoring language for embodied conversational agents

Embodied Conversational Agent (ECA) is the user interface metaphor that allows to naturally communicate information during human-computer interaction in synergic modality dimensions, including voice, gesture, emotion, text, etc. Due to its anthropological representation and the ability to express human-like behavior, ECAs are becoming popular interface front-ends for dialog and conversational applications. One important prerequisite for efficient authoring of such ECA-based applications is the existence of a suitable programming language that exploits the expressive possibilities of multimodally blended messages conveyed to the user. In this paper, we present an architecture and interaction language ECAF, which we used for authoring several ECA-based applications. We also provide the feedback from usability testing we carried for user acceptance of several multimodal blending strategies.